App Engine Python SDK version 1.7.7

[gae.git] / python / google / appengine / api / images / __init__.py

#!/usr/bin/env python
#
# Copyright 2007 Google Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#




"""Image manipulation API.

Classes defined in this module:
  Image: class used to encapsulate image information and transformations for
    that image.

    The current manipulations that are available are resize, rotate,
    horizontal_flip, vertical_flip, crop and im_feeling_lucky.

    It should be noted that each transform can only be called once per image
    per execute_transforms() call.
"""







import struct

try:
  import json
except:
  import simplejson as json

from google.appengine.api import apiproxy_stub_map
from google.appengine.api import blobstore
from google.appengine.api import datastore_types
from google.appengine.api.images import images_service_pb
from google.appengine.runtime import apiproxy_errors


BlobKey = datastore_types.BlobKey


JPEG = images_service_pb.OutputSettings.JPEG
PNG = images_service_pb.OutputSettings.PNG
WEBP = images_service_pb.OutputSettings.WEBP
BMP = -1
GIF = -2
ICO = -3
TIFF = -4

OUTPUT_ENCODING_TYPES = frozenset([JPEG, PNG, WEBP])

UNCHANGED_ORIENTATION = images_service_pb.InputSettings.UNCHANGED_ORIENTATION
CORRECT_ORIENTATION = images_service_pb.InputSettings.CORRECT_ORIENTATION

ORIENTATION_CORRECTION_TYPE = frozenset([UNCHANGED_ORIENTATION,
                                         CORRECT_ORIENTATION])

TOP_LEFT = images_service_pb.CompositeImageOptions.TOP_LEFT
TOP_CENTER = images_service_pb.CompositeImageOptions.TOP
TOP_RIGHT = images_service_pb.CompositeImageOptions.TOP_RIGHT
CENTER_LEFT = images_service_pb.CompositeImageOptions.LEFT
CENTER_CENTER = images_service_pb.CompositeImageOptions.CENTER
CENTER_RIGHT = images_service_pb.CompositeImageOptions.RIGHT
BOTTOM_LEFT = images_service_pb.CompositeImageOptions.BOTTOM_LEFT
BOTTOM_CENTER = images_service_pb.CompositeImageOptions.BOTTOM
BOTTOM_RIGHT = images_service_pb.CompositeImageOptions.BOTTOM_RIGHT

ANCHOR_TYPES = frozenset([TOP_LEFT, TOP_CENTER, TOP_RIGHT, CENTER_LEFT,
                          CENTER_CENTER, CENTER_RIGHT, BOTTOM_LEFT,
                          BOTTOM_CENTER, BOTTOM_RIGHT])



MAX_TRANSFORMS_PER_REQUEST = 10




MAX_COMPOSITES_PER_REQUEST = 16


class Error(Exception):
  """Base error class for this module."""


class TransformationError(Error):
  """Error while attempting to transform the image."""


class BadRequestError(Error):
  """The parameters given had something wrong with them."""


class NotImageError(Error):
  """The image data given is not recognizable as an image."""


class BadImageError(Error):
  """The image data given is corrupt."""


class LargeImageError(Error):
  """The image data given is too large to process."""


class InvalidBlobKeyError(Error):
  """The provided blob key was invalid."""

  def __init__(self, blob_key=None):
    """Constructor.

    Args:
      blob_key: The blob_key that is believed to be invalid. May be None if the
        BlobKey is unknown.
    """
    self._blob_key = blob_key

  def __str__(self):
    """Returns a string representation of this Error."""
    if self._blob_key:
      return 'InvalidBlobKeyError: %s' % repr(self._blob_key)
    else:
      return 'InvalidBlobKeyError'


class BlobKeyRequiredError(Error):
  """A blobkey is required for this operation."""


class UnsupportedSizeError(Error):
  """Specified size is not supported by requested operation."""


class AccessDeniedError(Error):
  """The application does not have permission to access the image."""


class ObjectNotFoundError(Error):
  """The object referred to by a BlobKey does not exist."""


def _ToImagesError(error, blob_key=None):
  """Translate an application error to an Images error, if possible.

  Args:
    error: an ApplicationError to translate.
    blob_key: The blob_key that used in the function that caused the error.
      May be None if the BlobKey is unknown.

   Returns:
     The Images error if found, otherwise the original error.
  """
  error_map = {
      images_service_pb.ImagesServiceError.NOT_IMAGE:
      NotImageError,
      images_service_pb.ImagesServiceError.BAD_IMAGE_DATA:
      BadImageError,
      images_service_pb.ImagesServiceError.IMAGE_TOO_LARGE:
      LargeImageError,
      images_service_pb.ImagesServiceError.INVALID_BLOB_KEY:
      InvalidBlobKeyError,
      images_service_pb.ImagesServiceError.ACCESS_DENIED:
      AccessDeniedError,
      images_service_pb.ImagesServiceError.OBJECT_NOT_FOUND:
      ObjectNotFoundError,
      images_service_pb.ImagesServiceError.UNSPECIFIED_ERROR:
      TransformationError,
      images_service_pb.ImagesServiceError.BAD_TRANSFORM_DATA:
      BadRequestError,
      }

  error_code = error.application_error

  if error_code == images_service_pb.ImagesServiceError.INVALID_BLOB_KEY:
    return InvalidBlobKeyError(blob_key)

  desired_exc = error_map.get(error_code, Error)
  return desired_exc(error.error_detail)


class Image(object):
  """Image object to manipulate."""

  def __init__(self, image_data=None, blob_key=None, filename=None):
    """Constructor.

    Only one of image_data, blob_key or filename can be specified.

    Args:
      image_data: str, image data in string form.
      blob_key: BlobKey, BlobInfo, str, or unicode representation of BlobKey of
        blob containing the image data.
      filename: str, the filename of a Google Storage file containing the
        image data. Must be in the format '/gs/bucket_name/object_name'.

    Raises:
      NotImageError if the given data is empty.
    """

    if not image_data and not blob_key and not filename:
      raise NotImageError("Empty image data.")
    if image_data and (blob_key or filename):
      raise NotImageError("Can only take one of image, blob key or filename.")
    if blob_key and filename:
      raise NotImageError("Can only take one of image, blob key or filename.")

    self._image_data = image_data
    if filename:
      self._blob_key = blobstore.create_gs_key(filename)
    else:
      self._blob_key = _extract_blob_key(blob_key)
    self._transforms = []
    self._width = None
    self._height = None
    self._format = None
    self._correct_orientation = UNCHANGED_ORIENTATION
    self._original_metadata = None

  def _check_transform_limits(self):
    """Ensure some simple limits on the number of transforms allowed.

    Raises:
      BadRequestError if MAX_TRANSFORMS_PER_REQUEST transforms have already been
      requested for this image
    """
    if len(self._transforms) >= MAX_TRANSFORMS_PER_REQUEST:
      raise BadRequestError("%d transforms have already been requested on this "
                            "image." % MAX_TRANSFORMS_PER_REQUEST)

  def _update_dimensions(self):
    """Updates the width and height fields of the image.

    Raises:
      NotImageError if the image data is not an image.
      BadImageError if the image data is corrupt.
    """
    if not self._image_data:
      raise NotImageError("Dimensions unavailable for blob key input")
    size = len(self._image_data)
    if size >= 6 and self._image_data.startswith("GIF"):
      self._update_gif_dimensions()
      self._format = GIF;
    elif size >= 8 and self._image_data.startswith("\x89PNG\x0D\x0A\x1A\x0A"):
      self._update_png_dimensions()
      self._format = PNG
    elif size >= 2 and self._image_data.startswith("\xff\xD8"):
      self._update_jpeg_dimensions()
      self._format = JPEG
    elif (size >= 8 and (self._image_data.startswith("II\x2a\x00") or
                         self._image_data.startswith("MM\x00\x2a"))):
      self._update_tiff_dimensions()
      self._format = TIFF
    elif size >= 2 and self._image_data.startswith("BM"):
      self._update_bmp_dimensions()
      self._format = BMP
    elif size >= 4 and self._image_data.startswith("\x00\x00\x01\x00"):
      self._update_ico_dimensions()
      self._format = ICO
    elif (size >= 16 and (self._image_data.startswith("RIFF", 0, 4) and
                          self._image_data.startswith("WEBP", 8, 12) and
                          self._image_data.startswith("VP8 ", 12, 16))):
      self._update_webp_dimensions()
      self._format = WEBP

    elif (size >= 16 and (self._image_data.startswith("RIFF", 0, 4) and
                          self._image_data.startswith("WEBP", 8, 12) and
                          self._image_data.startswith("VP8X", 12, 16))):
      self._update_webp_vp8x_dimensions()
      self._format = WEBP
    else:
      raise NotImageError("Unrecognized image format")

  def _update_gif_dimensions(self):
    """Updates the width and height fields of the gif image.

    Raises:
      BadImageError if the image string is not a valid gif image.
    """

    size = len(self._image_data)
    if size >= 10:
      self._width, self._height = struct.unpack("<HH", self._image_data[6:10])
    else:
      raise BadImageError("Corrupt GIF format")

  def _update_png_dimensions(self):
    """Updates the width and height fields of the png image.

    Raises:
      BadImageError if the image string is not a valid png image.
    """


    size = len(self._image_data)
    if size >= 24 and self._image_data[12:16] == "IHDR":
      self._width, self._height = struct.unpack(">II", self._image_data[16:24])
    else:
      raise BadImageError("Corrupt PNG format")

  def _update_jpeg_dimensions(self):
    """Updates the width and height fields of the jpeg image.

    Raises:
      BadImageError if the image string is not a valid jpeg image.
    """

    size = len(self._image_data)
    offset = 2
    while offset < size:
      while offset < size and ord(self._image_data[offset]) != 0xFF:
        offset += 1
      while offset < size and ord(self._image_data[offset]) == 0xFF:
        offset += 1
      if (offset < size and ord(self._image_data[offset]) & 0xF0 == 0xC0 and
          ord(self._image_data[offset]) != 0xC4):
        offset += 4
        if offset + 4 <= size:
          self._height, self._width = struct.unpack(
              ">HH",
              self._image_data[offset:offset + 4])
          break
        else:
          raise BadImageError("Corrupt JPEG format")
      elif offset + 3 <= size:
        offset += 1
        offset += struct.unpack(">H", self._image_data[offset:offset + 2])[0]
      else:
        raise BadImageError("Corrupt JPEG format")
    if self._height is None or self._width is None:
      raise BadImageError("Corrupt JPEG format")

  def _update_tiff_dimensions(self):
    """Updates the width and height fields of the tiff image.

    Raises:
      BadImageError if the image string is not a valid tiff image.
    """


    size = len(self._image_data)
    if self._image_data.startswith("II"):
      endianness = "<"
    else:
      endianness = ">"
    ifd_offset = struct.unpack(endianness + "I", self._image_data[4:8])[0]
    if ifd_offset + 14 <= size:
      ifd_size = struct.unpack(
          endianness + "H",
          self._image_data[ifd_offset:ifd_offset + 2])[0]
      ifd_offset += 2
      for unused_i in range(0, ifd_size):
        if ifd_offset + 12 <= size:
          tag = struct.unpack(
              endianness + "H",
              self._image_data[ifd_offset:ifd_offset + 2])[0]
          if tag == 0x100 or tag == 0x101:
            value_type = struct.unpack(
                endianness + "H",
                self._image_data[ifd_offset + 2:ifd_offset + 4])[0]
            if value_type == 3:
              format = endianness + "H"
              end_offset = ifd_offset + 10
            elif value_type == 4:
              format = endianness + "I"
              end_offset = ifd_offset + 12
            else:
              format = endianness + "B"
              end_offset = ifd_offset + 9
            if tag == 0x100:
              self._width = struct.unpack(
                  format,
                  self._image_data[ifd_offset + 8:end_offset])[0]
              if self._height is not None:
                break
            else:
              self._height = struct.unpack(
                  format,
                  self._image_data[ifd_offset + 8:end_offset])[0]
              if self._width is not None:
                break
          ifd_offset += 12
        else:
          raise BadImageError("Corrupt TIFF format")
    if self._width is None or self._height is None:
      raise BadImageError("Corrupt TIFF format")

  def _update_bmp_dimensions(self):
    """Updates the width and height fields of the bmp image.

    Raises:
      BadImageError if the image string is not a valid bmp image.
    """




    size = len(self._image_data)
    if size >= 18:
      header_length = struct.unpack("<I", self._image_data[14:18])[0]
      if ((header_length == 40 or header_length == 108 or
           header_length == 124 or header_length == 64) and size >= 26):

        self._width, self._height = struct.unpack("<II",
                                                  self._image_data[18:26])
      elif header_length == 12 and size >= 22:
        self._width, self._height = struct.unpack("<HH",
                                                  self._image_data[18:22])
      else:
        raise BadImageError("Corrupt BMP format")
    else:
      raise BadImageError("Corrupt BMP format")

  def _update_ico_dimensions(self):
    """Updates the width and height fields of the ico image.

    Raises:
      BadImageError if the image string is not a valid ico image.
    """
    size = len(self._image_data)
    if size >= 8:
      self._width, self._height = struct.unpack("<BB", self._image_data[6:8])

      if not self._width:
        self._width = 256
      if not self._height:
        self._height = 256
    else:
      raise BadImageError("Corrupt ICO format")

  def set_correct_orientation(self, correct_orientation):
    """Set flag to correct image orientation based on image metadata.

    EXIF metadata within the image may contain a parameter indicating its proper
    orientation. This value can equal 1 through 8, inclusive. "1" means that the
    image is in its "normal" orientation, i.e., it should be viewed as it is
    stored. Normally, this "orientation" value has no effect on the behavior of
    the transformations. However, calling this function with the value
    CORRECT_ORIENTATION any orientation specified in the EXIF metadata will be
    corrected during the first transformation.

    NOTE: If CORRECT_ORIENTATION is specified but the image is already in
    portrait orientation, i.e., "taller" than it is "wide" no corrections will
    be made, since it appears that the camera has already corrected it.

    Regardless whether the correction was requested or not, the orientation
    value in the transformed image is always cleared to indicate that no
    additional corrections of the returned image's orientation is necessary.

    Args:
      correct_orientation: a value from ORIENTATION_CORRECTION_TYPE.

    Raises:
      BadRequestError if correct_orientation value is invalid.
    """
    if correct_orientation not in ORIENTATION_CORRECTION_TYPE:
      raise BadRequestError("Orientation correction must be in %s" %
                            ORIENTATION_CORRECTION_TYPE)
    self._correct_orientation = correct_orientation


  def _update_webp_dimensions(self):
    """Updates the width and height fields of the webp image."""

    size = len(self._image_data)



    if size < 30:
      raise BadImageError("Corrupt WEBP format")

    bits = (ord(self._image_data[20]) | (ord(self._image_data[21])<<8) |
            (ord(self._image_data[22]) << 16))

    key_frame = ((bits & 1) == 0)

    if not key_frame:
      raise BadImageError("Corrupt WEBP format")

    profile = (bits >> 1) & 7
    show_frame = (bits >> 4) & 1

    if profile > 3:
      raise BadImageError("Corrupt WEBP format")

    if show_frame == 0:
      raise BadImageError("Corrupt WEBP format")

    self._width, self._height = struct.unpack("<HH", self._image_data[26:30])

    if self._height is None or self._width is None:
      raise BadImageError("Corrupt WEBP format")

  def _update_webp_vp8x_dimensions(self):
    """Updates the width and height fields of a webp image with vp8x chunk."""
    size = len(self._image_data)

    if size < 30:
      raise BadImageError("Corrupt WEBP format")

    self._width, self._height = struct.unpack("<II", self._image_data[24:32])

    if self._height is None or self._width is None:
      raise BadImageError("Corrupt WEBP format")

  def resize(self, width=0, height=0, crop_to_fit=False,
             crop_offset_x=0.5, crop_offset_y=0.5, allow_stretch=False):
    """Resize the image maintaining the aspect ratio.

    If both width and height are specified, the more restricting of the two
    values will be used when resizing the image. The maximum dimension allowed
    for both width and height is 4000 pixels.
    If both width and height are specified and crop_to_fit is True, the less
    restricting of the two values will be used when resizing and the image will
    be cropped to fit the specified size. In this case the center of cropping
    can be adjusted  by crop_offset_x and crop_offset_y.

    Args:
      width: int, width (in pixels) to change the image width to.
      height: int, height (in pixels) to change the image height to.
      crop_to_fit: If True and both width and height are specified, the image is
        cropped after resize to fit the specified dimensions.
      crop_offset_x: float value between 0.0 and 1.0, 0 is left and 1 is right,
        default is 0.5, the center of image.
      crop_offset_y: float value between 0.0 and 1.0, 0 is top and 1 is bottom,
        default is 0.5, the center of image.
      allow_stretch: If True and both width and height are specified, the image
        is stretched to fit the resize dimensions without maintaining the
        aspect ratio.

    Raises:
      TypeError when width or height is not either 'int' or 'long' types.
      BadRequestError when there is something wrong with the given height or
        width or if MAX_TRANSFORMS_PER_REQUEST transforms have already been
        requested on this image.
    """
    if (not isinstance(width, (int, long)) or
        not isinstance(height, (int, long))):
      raise TypeError("Width and height must be integers.")
    if width < 0 or height < 0:
      raise BadRequestError("Width and height must be >= 0.")

    if not width and not height:
      raise BadRequestError("At least one of width or height must be > 0.")

    if width > 4000 or height > 4000:
      raise BadRequestError("Both width and height must be <= 4000.")

    if not isinstance(crop_to_fit, bool):
      raise TypeError("crop_to_fit must be boolean.")

    if crop_to_fit and not (width and height):
      raise BadRequestError("Both width and height must be > 0 when "
                            "crop_to_fit is specified.")

    if not isinstance(allow_stretch, bool):
      raise TypeError("allow_stretch must be boolean.")

    if allow_stretch and not (width and height):
      raise BadRequestError("Both width and height must be > 0 when "
                            "allow_stretch is specified.")

    self._validate_crop_arg(crop_offset_x, "crop_offset_x")
    self._validate_crop_arg(crop_offset_y, "crop_offset_y")

    self._check_transform_limits()

    transform = images_service_pb.Transform()
    transform.set_width(width)
    transform.set_height(height)
    transform.set_crop_to_fit(crop_to_fit)
    transform.set_crop_offset_x(crop_offset_x)
    transform.set_crop_offset_y(crop_offset_y)
    transform.set_allow_stretch(allow_stretch)

    self._transforms.append(transform)

  def rotate(self, degrees):
    """Rotate an image a given number of degrees clockwise.

    Args:
      degrees: int, must be a multiple of 90.

    Raises:
      TypeError when degrees is not either 'int' or 'long' types.
      BadRequestError when there is something wrong with the given degrees or
      if MAX_TRANSFORMS_PER_REQUEST transforms have already been requested.
    """
    if not isinstance(degrees, (int, long)):
      raise TypeError("Degrees must be integers.")

    if degrees % 90 != 0:
      raise BadRequestError("degrees argument must be multiple of 90.")


    degrees = degrees % 360




    self._check_transform_limits()

    transform = images_service_pb.Transform()
    transform.set_rotate(degrees)

    self._transforms.append(transform)

  def horizontal_flip(self):
    """Flip the image horizontally.

    Raises:
      BadRequestError if MAX_TRANSFORMS_PER_REQUEST transforms have already been
      requested on the image.
    """
    self._check_transform_limits()

    transform = images_service_pb.Transform()
    transform.set_horizontal_flip(True)

    self._transforms.append(transform)

  def vertical_flip(self):
    """Flip the image vertically.

    Raises:
      BadRequestError if MAX_TRANSFORMS_PER_REQUEST transforms have already been
      requested on the image.
    """
    self._check_transform_limits()
    transform = images_service_pb.Transform()
    transform.set_vertical_flip(True)

    self._transforms.append(transform)

  def _validate_crop_arg(self, val, val_name):
    """Validate the given value of a Crop() method argument.

    Args:
      val: float, value of the argument.
      val_name: str, name of the argument.

    Raises:
      TypeError if the args are not of type 'float'.
      BadRequestError when there is something wrong with the given bounding box.
    """
    if type(val) != float:
      raise TypeError("arg '%s' must be of type 'float'." % val_name)

    if not (0 <= val <= 1.0):
      raise BadRequestError("arg '%s' must be between 0.0 and 1.0 "
                            "(inclusive)" % val_name)

  def crop(self, left_x, top_y, right_x, bottom_y):
    """Crop the image.

    The four arguments are the scaling numbers to describe the bounding box
    which will crop the image.  The upper left point of the bounding box will
    be at (left_x*image_width, top_y*image_height) the lower right point will
    be at (right_x*image_width, bottom_y*image_height).

    Args:
      left_x: float value between 0.0 and 1.0 (inclusive).
      top_y: float value between 0.0 and 1.0 (inclusive).
      right_x: float value between 0.0 and 1.0 (inclusive).
      bottom_y: float value between 0.0 and 1.0 (inclusive).

    Raises:
      TypeError if the args are not of type 'float'.
      BadRequestError when there is something wrong with the given bounding box
        or if MAX_TRANSFORMS_PER_REQUEST transforms have already been requested
        for this image.
    """
    self._validate_crop_arg(left_x, "left_x")
    self._validate_crop_arg(top_y, "top_y")
    self._validate_crop_arg(right_x, "right_x")
    self._validate_crop_arg(bottom_y, "bottom_y")

    if left_x >= right_x:
      raise BadRequestError("left_x must be less than right_x")
    if top_y >= bottom_y:
      raise BadRequestError("top_y must be less than bottom_y")

    self._check_transform_limits()

    transform = images_service_pb.Transform()
    transform.set_crop_left_x(left_x)
    transform.set_crop_top_y(top_y)
    transform.set_crop_right_x(right_x)
    transform.set_crop_bottom_y(bottom_y)

    self._transforms.append(transform)

  def im_feeling_lucky(self):
    """Automatically adjust image contrast and color levels.

    This is similar to the "I'm Feeling Lucky" button in Picasa.

    Raises:
      BadRequestError if MAX_TRANSFORMS_PER_REQUEST transforms have already
        been requested for this image.
    """
    self._check_transform_limits()
    transform = images_service_pb.Transform()
    transform.set_autolevels(True)

    self._transforms.append(transform)

  def get_original_metadata(self):
    """Metadata of the original image.

    Returns a dictionary of metadata extracted from the original image during
    execute_transform.
    Note, that some of the EXIF fields are processed, e.g., fields with multiple
    values returned as lists, rational types are returned as floats, GPS
    coordinates already parsed to signed floats, etc.
    ImageWidth and ImageLength fields are corrected if they did not correspond
    to the actual dimensions of the original image.

    Returns:
      dict with string keys. If execute_transform was called with parse_metadata
      being True, this dictionary contains information about various properties
      of the original image, such as dimensions, color profile, and properties
      from EXIF.
      Even if parse_metadata was False or the images did not have any metadata,
      the dictionary will contain a limited set of metadata, at least
      'ImageWidth' and 'ImageLength', corresponding to the dimensions of the
      original image.
      It will return None, if it is called before a successful
      execute_transfrom.
    """
    return self._original_metadata

  def _set_imagedata(self, imagedata):
    """Fills in an ImageData PB from this Image instance.

    Args:
      imagedata: An ImageData PB instance
    """
    if self._blob_key:
      imagedata.set_content("")
      imagedata.set_blob_key(self._blob_key)
    else:
      imagedata.set_content(self._image_data)

  def execute_transforms(self, output_encoding=PNG, quality=None,
                         parse_source_metadata=False,
                         transparent_substitution_rgb=None,
                         rpc=None):
    """Perform transformations on a given image.

    Args:
      output_encoding: A value from OUTPUT_ENCODING_TYPES.
      quality: A value between 1 and 100 to specify the quality of the
        encoding.  This value is only used for JPEG & WEBP quality control.
      parse_source_metadata: when True the metadata (EXIF) of the source image
        is parsed before any transformations. The results can be retrieved
        via Image.get_original_metadata.
      transparent_substition_rgb: When transparent pixels are not support in the
        destination image format then transparent pixels will be substituted
        for the specified color, which must be 32 bit rgb format.
      rpc: A UserRPC object.

    Returns:
      str, image data after the transformations have been performed on it.

    Raises:
      BadRequestError when there is something wrong with the request
        specifications.
      NotImageError when the image data given is not an image.
      BadImageError when the image data given is corrupt.
      LargeImageError when the image data given is too large to process.
      InvalidBlobKeyError when the blob key provided is invalid.
      TransformtionError when something errors during image manipulation.
      AccessDeniedError: when the blobkey refers to a Google Storage object, and
        the application does not have permission to access the object.
      ObjectNotFoundError:: when the blobkey refers to an object that no longer
        exists.
      Error when something unknown, but bad, happens.
    """
    rpc = self.execute_transforms_async(output_encoding=output_encoding,
        quality=quality,
        parse_source_metadata=parse_source_metadata,
        transparent_substitution_rgb=transparent_substitution_rgb,
        rpc=rpc)
    return rpc.get_result()

  def execute_transforms_async(self, output_encoding=PNG, quality=None,
                               parse_source_metadata=False,
                               transparent_substitution_rgb=None,
                               rpc=None):
    """Perform transformations on a given image - async version.

    Args:
      output_encoding: A value from OUTPUT_ENCODING_TYPES.
      quality: A value between 1 and 100 to specify the quality of the
        encoding.  This value is only used for JPEG & WEBP quality control.
      parse_source_metadata: when True the metadata (EXIF) of the source image
        is parsed before any transformations. The results can be retrieved
        via Image.get_original_metadata.
      transparent_substition_rgb: When transparent pixels are not support in the
        destination image format then transparent pixels will be substituted
        for the specified color, which must be 32 bit rgb format.
      rpc: A UserRPC object.

    Returns:
      A UserRPC object.

    Raises:
      BadRequestError when there is something wrong with the request
        specifications.
      NotImageError when the image data given is not an image.
      BadImageError when the image data given is corrupt.
      LargeImageError when the image data given is too large to process.
      InvalidBlobKeyError when the blob key provided is invalid.
      TransformtionError when something errors during image manipulation.
      AccessDeniedError: when the blobkey refers to a Google Storage object, and
        the application does not have permission to access the object.
      ValueError: when transparent_substitution_rgb is not an integer
      Error when something unknown, but bad, happens.
    """
    if output_encoding not in OUTPUT_ENCODING_TYPES:
      raise BadRequestError("Output encoding type not in recognized set "
                            "%s" % OUTPUT_ENCODING_TYPES)

    if not self._transforms:
      raise BadRequestError("Must specify at least one transformation.")

    if transparent_substitution_rgb:
      if not isinstance(transparent_substitution_rgb, int):
        raise ValueError(
            "transparent_substitution_rgb must be a 32 bit integer")

    self.CheckValidIntParameter(quality, 1, 100, "quality")

    request = images_service_pb.ImagesTransformRequest()
    response = images_service_pb.ImagesTransformResponse()

    input_settings = request.mutable_input()
    input_settings.set_correct_exif_orientation(
        self._correct_orientation)

    if parse_source_metadata:
      input_settings.set_parse_metadata(True)

    self._set_imagedata(request.mutable_image())

    for transform in self._transforms:
      request.add_transform().CopyFrom(transform)

    request.mutable_output().set_mime_type(output_encoding)

    if ((output_encoding == JPEG or output_encoding == WEBP) and
        (quality is not None)):
      request.mutable_output().set_quality(quality)

    if transparent_substitution_rgb:
      input_settings.set_transparent_substitution_rgb(
          transparent_substitution_rgb)

    def execute_transforms_hook(rpc):
      """Check success, handles exceptions and returns the converted RPC result.

      Args:
        rpc: A UserRPC object.

      Raises:
        See docstring for execute_transforms_async for more details.
      """
      try:
        rpc.check_success()
      except apiproxy_errors.ApplicationError, e:
        raise _ToImagesError(e, self._blob_key)
      self._image_data = rpc.response.image().content()
      self._blob_key = None
      self._transforms = []
      if response.image().has_width():
        self._width = rpc.response.image().width()
      else:
        self._width = None
      if response.image().has_height():
        self._height = rpc.response.image().height()
      else:
        self._height = None
      self._format = None
      if response.source_metadata():
        self._original_metadata = json.loads(response.source_metadata())
      return self._image_data

    return _make_async_call(rpc,
                            "Transform",
                            request,
                            response,
                            execute_transforms_hook,
                            None)

  @property
  def width(self):
    """Gets the width of the image."""
    if self._width is None:
      self._update_dimensions()
    return self._width

  @property
  def height(self):
    """Gets the height of the image."""
    if self._height is None:
      self._update_dimensions()
    return self._height

  @property
  def format(self):
    """Gets the format of the image."""
    if self._format is None:
      self._update_dimensions()
    return self._format

  def histogram(self, rpc=None):
    """Calculates the histogram of the image.

    Args:
      rpc: A UserRPC object.

    Returns: 3 256-element lists containing the number of occurences of each
    value of each color in the order RGB. As described at
    http://en.wikipedia.org/wiki/Color_histogram for N = 256. i.e. the first
    value of the first list contains the number of pixels with a red value of
    0, the second the number with a red value of 1.

    Raises:
      NotImageError when the image data given is not an image.
      BadImageError when the image data given is corrupt.
      LargeImageError when the image data given is too large to process.
      Error when something unknown, but bad, happens.
    """

    rpc = self.histogram_async(rpc)
    return rpc.get_result()

  def histogram_async(self, rpc=None):
    """Calculates the histogram of the image - async version.

    Args:
      rpc: An optional UserRPC object.

    Returns:
      rpc: A UserRPC object.

    Raises:
      NotImageError when the image data given is not an image.
      BadImageError when the image data given is corrupt.
      LargeImageError when the image data given is too large to process.
      Error when something unknown, but bad, happens.
    """
    request = images_service_pb.ImagesHistogramRequest()
    response = images_service_pb.ImagesHistogramResponse()

    self._set_imagedata(request.mutable_image())

    def get_histogram_hook(rpc):
      """Check success, handles exceptions and returns the converted RPC result.

      Args:
        rpc: A UserRPC object.

      Raises:
        See docstring for histogram_async for more details.
      """
      try:
        rpc.check_success()
      except apiproxy_errors.ApplicationError, e:
        raise _ToImagesError(e, self._blob_key)

      histogram = rpc.response.histogram()
      return [histogram.red_list(),
              histogram.green_list(),
              histogram.blue_list()]

    return _make_async_call(rpc,
                            "Histogram",
                            request,
                            response,
                            get_histogram_hook,
                            None)

  @staticmethod
  def CheckValidIntParameter(parameter, min_value, max_value, name):
    """Checks that a parameters is an integer within the specified range."""

    if parameter is not None:
      if not isinstance(parameter, (int, long)):
        raise TypeError("%s must be an integer." % name)
      if parameter > max_value or parameter < min_value:
        raise BadRequestError("%s must be between %s and %s."
                              % name, str(min_value), str(max_value))








def create_rpc(deadline=None, callback=None):
  """Creates an RPC object for use with the images API.

  Args:
    deadline: Optional deadline in seconds for the operation; the default
      is a system-specific deadline (typically 5 seconds).
    callback: Optional callable to invoke on completion.

  Returns:
    An apiproxy_stub_map.UserRPC object specialized for this service.
  """
  return apiproxy_stub_map.UserRPC("images", deadline, callback)


def _make_async_call(rpc, method, request, response,
                     get_result_hook, user_data):
  if rpc is None:
    rpc = create_rpc()
  rpc.make_call(method, request, response, get_result_hook, user_data)
  return rpc


def resize(image_data, width=0, height=0, output_encoding=PNG, quality=None,
           correct_orientation=UNCHANGED_ORIENTATION,
           crop_to_fit=False, crop_offset_x=0.5, crop_offset_y=0.5,
           allow_stretch=False, rpc=None, transparent_substitution_rgb=None):
  """Resize a given image file maintaining the aspect ratio.

  If both width and height are specified, the more restricting of the two
  values will be used when resizing the image. The maximum dimension allowed
  for both width and height is 4000 pixels.
  If both width and height are specified and crop_to_fit is True, the less
  restricting of the two values will be used when resizing and the image will be
  cropped to fit the specified size. In this case the center of cropping can be
  adjusted  by crop_offset_x and crop_offset_y.

  Args:
    image_data: str, source image data.
    width: int, width (in pixels) to change the image width to.
    height: int, height (in pixels) to change the image height to.
    output_encoding: a value from OUTPUT_ENCODING_TYPES.
    quality: A value between 1 and 100 to specify the quality of the
      encoding.  This value is only used for JPEG quality control.
    correct_orientation: one of ORIENTATION_CORRECTION_TYPE, to indicate if
      orientation correction should be performed during the transformation.
    crop_to_fit: If True and both width and height are specified, the image is
      cropped after resize to fit the specified dimensions.
    crop_offset_x: float value between 0.0 and 1.0, 0 is left and 1 is right,
      default is 0.5, the center of image.
    crop_offset_y: float value between 0.0 and 1.0, 0 is top and 1 is bottom,
      default is 0.5, the center of image.
    allow_stretch: If True and both width and height are specified, the image
      is stretched to fit the resize dimensions without maintaining the
      aspect ratio.
    rpc: Optional UserRPC object.
    transparent_substition_rgb: When transparent pixels are not support in the
      destination image format then transparent pixels will be substituted
      for the specified color, which must be 32 bit rgb format.

  Raises:
    TypeError when width or height not either 'int' or 'long' types.
    BadRequestError when there is something wrong with the given height or
      width.
    Error when something went wrong with the call.  See Image.ExecuteTransforms
      for more details.
  """
  rpc = resize_async(image_data,
                     width=width,
                     height=height,
                     output_encoding=output_encoding,
                     quality=quality,
                     correct_orientation=correct_orientation,
                     crop_to_fit=crop_to_fit,
                     crop_offset_x=crop_offset_x,
                     crop_offset_y=crop_offset_y,
                     allow_stretch=allow_stretch,
                     rpc=rpc,
                     transparent_substitution_rgb=transparent_substitution_rgb)
  return rpc.get_result()


def resize_async(image_data, width=0, height=0, output_encoding=PNG,
                 quality=None, correct_orientation=UNCHANGED_ORIENTATION,
                 crop_to_fit=False, crop_offset_x=0.5, crop_offset_y=0.5,
                 allow_stretch=False, rpc=None,
                 transparent_substitution_rgb=None):
  """Resize a given image file maintaining the aspect ratio - async version.

  If both width and height are specified, the more restricting of the two
  values will be used when resizing the image. The maximum dimension allowed
  for both width and height is 4000 pixels.
  If both width and height are specified and crop_to_fit is True, the less
  restricting of the two values will be used when resizing and the image will be
  cropped to fit the specified size. In this case the center of cropping can be
  adjusted  by crop_offset_x and crop_offset_y.

  Args:
    image_data: str, source image data.
    width: int, width (in pixels) to change the image width to.
    height: int, height (in pixels) to change the image height to.
    output_encoding: a value from OUTPUT_ENCODING_TYPES.
    quality: A value between 1 and 100 to specify the quality of the
      encoding.  This value is only used for JPEG quality control.
    correct_orientation: one of ORIENTATION_CORRECTION_TYPE, to indicate if
      orientation correction should be performed during the transformation.
    crop_to_fit: If True and both width and height are specified, the image is
      cropped after resize to fit the specified dimensions.
    crop_offset_x: float value between 0.0 and 1.0, 0 is left and 1 is right,
      default is 0.5, the center of image.
    crop_offset_y: float value between 0.0 and 1.0, 0 is top and 1 is bottom,
      default is 0.5, the center of image.
    allow_stretch: If True and both width and height are specified, the image
      is stretched to fit the resize dimensions without maintaining the
      aspect ratio.
    rpc: A UserRPC object.
    transparent_substition_rgb: When transparent pixels are not support in the
      destination image format then transparent pixels will be substituted
      for the specified color, which must be 32 bit rgb format.

  Returns:
    A UserRPC object, call get_result() to obtain the result of the RPC.

  Raises:
    TypeError when width or height not either 'int' or 'long' types.
    BadRequestError when there is something wrong with the given height or
      width.
    Error when something went wrong with the call.  See Image.ExecuteTransforms
      for more details.
  """
  image = Image(image_data)
  image.resize(width, height, crop_to_fit=crop_to_fit,
               crop_offset_x=crop_offset_x, crop_offset_y=crop_offset_y,
               allow_stretch=allow_stretch)
  image.set_correct_orientation(correct_orientation)
  return image.execute_transforms_async(output_encoding=output_encoding,
      quality=quality,
      rpc=rpc,
      transparent_substitution_rgb=transparent_substitution_rgb)


def rotate(image_data, degrees, output_encoding=PNG, quality=None,
           correct_orientation=UNCHANGED_ORIENTATION, rpc=None,
           transparent_substitution_rgb=None):
  """Rotate a given image a given number of degrees clockwise.

  Args:
    image_data: str, source image data.
    degrees: value from ROTATE_DEGREE_VALUES.
    output_encoding: a value from OUTPUT_ENCODING_TYPES.
    quality: A value between 1 and 100 to specify the quality of the
      encoding.  This value is only used for JPEG quality control.
    correct_orientation: one of ORIENTATION_CORRECTION_TYPE, to indicate if
      orientation correction should be performed during the transformation.
    rpc: An optional UserRPC object.
    transparent_substition_rgb: When transparent pixels are not support in the
      destination image format then transparent pixels will be substituted
      for the specified color, which must be 32 bit rgb format.

  Raises:
    TypeError when degrees is not either 'int' or 'long' types.
    BadRequestError when there is something wrong with the given degrees.
    Error when something went wrong with the call.  See Image.ExecuteTransforms
      for more details.
  """
  rpc = rotate_async(image_data,
      degrees,
      output_encoding=output_encoding,
      quality=quality,
      correct_orientation=correct_orientation,
      rpc=rpc,
      transparent_substitution_rgb=transparent_substitution_rgb)
  return rpc.get_result()


def rotate_async(image_data, degrees, output_encoding=PNG, quality=None,
                 correct_orientation=UNCHANGED_ORIENTATION, rpc=None,
                 transparent_substitution_rgb=None):
  """Rotate a given image a given number of degrees clockwise - async version.

  Args:
    image_data: str, source image data.
    degrees: value from ROTATE_DEGREE_VALUES.
    output_encoding: a value from OUTPUT_ENCODING_TYPES.
    quality: A value between 1 and 100 to specify the quality of the
      encoding.  This value is only used for JPEG quality control.
    correct_orientation: one of ORIENTATION_CORRECTION_TYPE, to indicate if
      orientation correction should be performed during the transformation.
    rpc: An optional UserRPC object.
    transparent_substition_rgb: When transparent pixels are not support in the
      destination image format then transparent pixels will be substituted
      for the specified color, which must be 32 bit rgb format.

  Returns:
    A UserRPC object, call get_result to complete the RPC and obtain the crop
      result.

  Raises:
    TypeError when degrees is not either 'int' or 'long' types.
    BadRequestError when there is something wrong with the given degrees.
    Error when something went wrong with the call.  See Image.ExecuteTransforms
      for more details.
  """
  image = Image(image_data)
  image.rotate(degrees)
  image.set_correct_orientation(correct_orientation)
  return image.execute_transforms_async(output_encoding=output_encoding,
      quality=quality,
      rpc=rpc,
      transparent_substitution_rgb=transparent_substitution_rgb)


def horizontal_flip(image_data, output_encoding=PNG, quality=None,
                    correct_orientation=UNCHANGED_ORIENTATION, rpc=None,
                    transparent_substitution_rgb=None):
  """Flip the image horizontally.

  Args:
    image_data: str, source image data.
    output_encoding: a value from OUTPUT_ENCODING_TYPES.
    quality: A value between 1 and 100 to specify the quality of the
      encoding.  This value is only used for JPEG quality control.
    correct_orientation: one of ORIENTATION_CORRECTION_TYPE, to indicate if
      orientation correction should be performed during the transformation.
    rpc: An Optional UserRPC object
    transparent_substition_rgb: When transparent pixels are not support in the
      destination image format then transparent pixels will be substituted
      for the specified color, which must be 32 bit rgb format.

  Raises:
    Error when something went wrong with the call.  See Image.ExecuteTransforms
      for more details.
  """
  rpc = horizontal_flip_async(image_data,
      output_encoding=output_encoding,
      quality=quality,
      correct_orientation=correct_orientation,
      rpc=rpc,
      transparent_substitution_rgb=transparent_substitution_rgb)
  return rpc.get_result()


def horizontal_flip_async(image_data, output_encoding=PNG, quality=None,
                          correct_orientation=UNCHANGED_ORIENTATION,
                          rpc=None,
                          transparent_substitution_rgb=None):
  """Flip the image horizontally - async version.

  Args:
    image_data: str, source image data.
    output_encoding: a value from OUTPUT_ENCODING_TYPES.
    quality: A value between 1 and 100 to specify the quality of the
      encoding.  This value is only used for JPEG quality control.
    correct_orientation: one of ORIENTATION_CORRECTION_TYPE, to indicate if
      orientation correction should be performed during the transformation.
    rpc: An Optional UserRPC object
    transparent_substition_rgb: When transparent pixels are not support in the
      destination image format then transparent pixels will be substituted
      for the specified color, which must be 32 bit rgb format.

  Returns:
    A UserRPC object, call get_result to complete the RPC and obtain the crop
      result.

  Raises:
    Error when something went wrong with the call.  See Image.ExecuteTransforms
      for more details.
  """
  image = Image(image_data)
  image.horizontal_flip()
  image.set_correct_orientation(correct_orientation)
  return image.execute_transforms_async(output_encoding=output_encoding,
      quality=quality,
      rpc=rpc,
      transparent_substitution_rgb=transparent_substitution_rgb)


def vertical_flip(image_data, output_encoding=PNG, quality=None,
                  correct_orientation=UNCHANGED_ORIENTATION, rpc=None,
                  transparent_substitution_rgb=None):
  """Flip the image vertically.

  Args:
    image_data: str, source image data.
    output_encoding: a value from OUTPUT_ENCODING_TYPES.
    quality: A value between 1 and 100 to specify the quality of the
      encoding.  This value is only used for JPEG quality control.
    correct_orientation: one of ORIENTATION_CORRECTION_TYPE, to indicate if
      orientation correction should be performed during the transformation.
    rpc: An Optional UserRPC object
    transparent_substition_rgb: When transparent pixels are not support in the
      destination image format then transparent pixels will be substituted
      for the specified color, which must be 32 bit rgb format.

  Raises:
    Error when something went wrong with the call.  See Image.ExecuteTransforms
      for more details.
  """
  rpc = vertical_flip_async(image_data,
      output_encoding=output_encoding,
      quality=quality,
      correct_orientation=correct_orientation,
      rpc=rpc,
      transparent_substitution_rgb=transparent_substitution_rgb)
  return rpc.get_result()


def vertical_flip_async(image_data, output_encoding=PNG, quality=None,
                        correct_orientation=UNCHANGED_ORIENTATION, rpc=None,
                        transparent_substitution_rgb=None):
  """Flip the image vertically - async version.

  Args:
    image_data: str, source image data.
    output_encoding: a value from OUTPUT_ENCODING_TYPES.
    quality: A value between 1 and 100 to specify the quality of the
      encoding.  This value is only used for JPEG quality control.
    correct_orientation: one of ORIENTATION_CORRECTION_TYPE, to indicate if
      orientation correction should be performed during the transformation.
    rpc: An Optional UserRPC object
    transparent_substition_rgb: When transparent pixels are not support in the
      destination image format then transparent pixels will be substituted
      for the specified color, which must be 32 bit rgb format.

  Returns:
    A UserRPC object, call get_result to complete the RPC and obtain the crop
      result.

  Raises:
    Error when something went wrong with the call.  See Image.ExecuteTransforms
      for more details.
  """
  image = Image(image_data)
  image.vertical_flip()
  image.set_correct_orientation(correct_orientation)
  return image.execute_transforms_async(output_encoding=output_encoding,
      quality=quality,
      rpc=rpc,
      transparent_substitution_rgb=transparent_substitution_rgb)


def crop(image_data, left_x, top_y, right_x, bottom_y, output_encoding=PNG,
         quality=None, correct_orientation=UNCHANGED_ORIENTATION, rpc=None,
         transparent_substitution_rgb=None):
  """Crop the given image.

  The four arguments are the scaling numbers to describe the bounding box
  which will crop the image.  The upper left point of the bounding box will
  be at (left_x*image_width, top_y*image_height) the lower right point will
  be at (right_x*image_width, bottom_y*image_height).

  Args:
    image_data: str, source image data.
    left_x: float value between 0.0 and 1.0 (inclusive).
    top_y: float value between 0.0 and 1.0 (inclusive).
    right_x: float value between 0.0 and 1.0 (inclusive).
    bottom_y: float value between 0.0 and 1.0 (inclusive).
    output_encoding: a value from OUTPUT_ENCODING_TYPES.
    quality: A value between 1 and 100 to specify the quality of the
      encoding.  This value is only used for JPEG quality control.
    correct_orientation: one of ORIENTATION_CORRECTION_TYPE, to indicate if
      orientation correction should be performed during the transformation.
    rpc: A User RPC Object
    transparent_substition_rgb: When transparent pixels are not support in the
      destination image format then transparent pixels will be substituted
      for the specified color, which must be 32 bit rgb format.

  Raises:
    TypeError if the args are not of type 'float'.
    BadRequestError when there is something wrong with the given bounding box.
    Error when something went wrong with the call.  See Image.ExecuteTransforms
      for more details.
  """
  rpc = crop_async(image_data, left_x, top_y, right_x, bottom_y,
                   output_encoding=output_encoding, quality=quality,
                   correct_orientation=correct_orientation, rpc=rpc,
                   transparent_substitution_rgb=transparent_substitution_rgb)
  return rpc.get_result()


def crop_async(image_data, left_x, top_y, right_x, bottom_y,
               output_encoding=PNG, quality=None,
               correct_orientation=UNCHANGED_ORIENTATION, rpc=None,
               transparent_substitution_rgb=None):
  """Crop the given image - async version.

  The four arguments are the scaling numbers to describe the bounding box
  which will crop the image.  The upper left point of the bounding box will
  be at (left_x*image_width, top_y*image_height) the lower right point will
  be at (right_x*image_width, bottom_y*image_height).

  Args:
    image_data: str, source image data.
    left_x: float value between 0.0 and 1.0 (inclusive).
    top_y: float value between 0.0 and 1.0 (inclusive).
    right_x: float value between 0.0 and 1.0 (inclusive).
    bottom_y: float value between 0.0 and 1.0 (inclusive).
    output_encoding: a value from OUTPUT_ENCODING_TYPES.
    quality: A value between 1 and 100 to specify the quality of the
      encoding.  This value is only used for JPEG quality control.
    correct_orientation: one of ORIENTATION_CORRECTION_TYPE, to indicate if
      orientation correction should be performed during the transformation.
    rpc: An optional UserRPC object.
    transparent_substition_rgb: When transparent pixels are not support in the
      destination image format then transparent pixels will be substituted
      for the specified color, which must be 32 bit rgb format.

  Returns:
    A UserRPC object, call get_result to complete the RPC and obtain the crop
      result.

  Raises:
    TypeError if the args are not of type 'float'.
    BadRequestError when there is something wrong with the given bounding box.
    Error when something went wrong with the call.  See Image.ExecuteTransforms
      for more details.
  """
  image = Image(image_data)
  image.crop(left_x, top_y, right_x, bottom_y)
  image.set_correct_orientation(correct_orientation)
  return image.execute_transforms_async(output_encoding=output_encoding,
      quality=quality,
      rpc=rpc,
      transparent_substitution_rgb=transparent_substitution_rgb)


def im_feeling_lucky(image_data, output_encoding=PNG, quality=None,
                     correct_orientation=UNCHANGED_ORIENTATION, rpc=None,
                     transparent_substitution_rgb=None):
  """Automatically adjust image levels.

  This is similar to the "I'm Feeling Lucky" button in Picasa.

  Args:
    image_data: str, source image data.
    output_encoding: a value from OUTPUT_ENCODING_TYPES.
    quality: A value between 1 and 100 to specify the quality of the
      encoding.  This value is only used for JPEG quality control.
    correct_orientation: one of ORIENTATION_CORRECTION_TYPE, to indicate if
      orientation correction should be performed during the transformation.
    rpc: An optional UserRPC object.
    transparent_substition_rgb: When transparent pixels are not support in the
      destination image format then transparent pixels will be substituted
      for the specified color, which must be 32 bit rgb format.

  Raises:
    Error when something went wrong with the call.  See Image.ExecuteTransforms
      for more details.
  """
  rpc = im_feeling_lucky_async(image_data,
      output_encoding=output_encoding,
      quality=quality,
      correct_orientation=correct_orientation,
      rpc=rpc,
      transparent_substitution_rgb=transparent_substitution_rgb)
  return rpc.get_result()


def im_feeling_lucky_async(image_data, output_encoding=PNG, quality=None,
                           correct_orientation=UNCHANGED_ORIENTATION, rpc=None,
                           transparent_substitution_rgb=None):
  """Automatically adjust image levels - async version.

  This is similar to the "I'm Feeling Lucky" button in Picasa.

  Args:
    image_data: str, source image data.
    output_encoding: a value from OUTPUT_ENCODING_TYPES.
    quality: A value between 1 and 100 to specify the quality of the
      encoding.  This value is only used for JPEG quality control.
    correct_orientation: one of ORIENTATION_CORRECTION_TYPE, to indicate if
      orientation correction should be performed during the transformation.
    rpc: An optional UserRPC object.
    transparent_substition_rgb: When transparent pixels are not support in the
      destination image format then transparent pixels will be substituted
      for the specified color, which must be 32 bit rgb format.

  Returns:
    A UserRPC object.

  Raises:
    Error when something went wrong with the call.  See Image.ExecuteTransforms
      for more details.
  """
  image = Image(image_data)
  image.im_feeling_lucky()
  image.set_correct_orientation(correct_orientation)
  return image.execute_transforms_async(output_encoding=output_encoding,
      quality=quality,
      rpc=rpc,
      transparent_substitution_rgb=transparent_substitution_rgb)


def composite(inputs, width, height, color=0, output_encoding=PNG,
              quality=None, rpc=None):
  """Composite one or more images onto a canvas - async version.

  Args:
    inputs: a list of tuples (image_data, x_offset, y_offset, opacity, anchor)
    where
      image_data: str, source image data.
      x_offset: x offset in pixels from the anchor position
      y_offset: y offset in piyels from the anchor position
      opacity: opacity of the image specified as a float in range [0.0, 1.0]
      anchor: anchoring point from ANCHOR_POINTS. The anchor point of the image
      is aligned with the same anchor point of the canvas. e.g. TOP_RIGHT would
      place the top right corner of the image at the top right corner of the
      canvas then apply the x and y offsets.
    width: canvas width in pixels.
    height: canvas height in pixels.
    color: canvas background color encoded as a 32 bit unsigned int where each
      color channel is represented by one byte in order ARGB.
    output_encoding: a value from OUTPUT_ENCODING_TYPES.
    quality: A value between 1 and 100 to specify the quality of the
      encoding. This value is only used for JPEG quality control.
    rpc: Optional UserRPC object.

  Returns:
      str, image data of the composited image.

  Raises:
    TypeError If width, height, color, x_offset or y_offset are not of type
    int or long or if opacity is not a float
    BadRequestError If more than MAX_TRANSFORMS_PER_REQUEST compositions have
    been requested, if the canvas width or height is greater than 4000 or less
    than or equal to 0, if the color is invalid or if for any composition
    option, the opacity is outside the range [0,1] or the anchor is invalid.
  """
  rpc = composite_async(inputs, width, height, color=color,
                        output_encoding=output_encoding, quality=quality,
                        rpc=rpc)
  return rpc.get_result()


def composite_async(inputs, width, height, color=0, output_encoding=PNG,
                    quality=None, rpc=None):
  """Composite one or more images onto a canvas - async version.

  Args:
    inputs: a list of tuples (image_data, x_offset, y_offset, opacity, anchor)
    where
      image_data: str, source image data.
      x_offset: x offset in pixels from the anchor position
      y_offset: y offset in piyels from the anchor position
      opacity: opacity of the image specified as a float in range [0.0, 1.0]
      anchor: anchoring point from ANCHOR_POINTS. The anchor point of the image
      is aligned with the same anchor point of the canvas. e.g. TOP_RIGHT would
      place the top right corner of the image at the top right corner of the
      canvas then apply the x and y offsets.
    width: canvas width in pixels.
    height: canvas height in pixels.
    color: canvas background color encoded as a 32 bit unsigned int where each
      color channel is represented by one byte in order ARGB.
    output_encoding: a value from OUTPUT_ENCODING_TYPES.
    quality: A value between 1 and 100 to specify the quality of the
      encoding. This value is only used for JPEG quality control.
    rpc: Optional UserRPC object.

  Returns:
      A UserRPC object.

  Raises:
    TypeError If width, height, color, x_offset or y_offset are not of type
    int or long or if opacity is not a float
    BadRequestError If more than MAX_TRANSFORMS_PER_REQUEST compositions have
    been requested, if the canvas width or height is greater than 4000 or less
    than or equal to 0, if the color is invalid or if for any composition
    option, the opacity is outside the range [0,1] or the anchor is invalid.
  """
  if (not isinstance(width, (int, long)) or
      not isinstance(height, (int, long)) or
      not isinstance(color, (int, long))):
    raise TypeError("Width, height and color must be integers.")
  if output_encoding not in OUTPUT_ENCODING_TYPES:
    raise BadRequestError("Output encoding type '%s' not in recognized set "
                          "%s" % (output_encoding, OUTPUT_ENCODING_TYPES))

  if quality is not None:
    if not isinstance(quality, (int, long)):
      raise TypeError("Quality must be an integer.")
    if quality > 100 or quality < 1:
      raise BadRequestError("Quality must be between 1 and 100.")

  if not inputs:
    raise BadRequestError("Must provide at least one input")
  if len(inputs) > MAX_COMPOSITES_PER_REQUEST:
    raise BadRequestError("A maximum of %d composition operations can be"
                          "performed in a single request" %
                          MAX_COMPOSITES_PER_REQUEST)

  if width <= 0 or height <= 0:
    raise BadRequestError("Width and height must be > 0.")
  if width > 4000 or height > 4000:
    raise BadRequestError("Width and height must be <= 4000.")

  if color > 0xffffffff or color < 0:
    raise BadRequestError("Invalid color")

  if color >= 0x80000000:
    color -= 0x100000000

  image_map = {}

  request = images_service_pb.ImagesCompositeRequest()
  response = images_service_pb.ImagesTransformResponse()
  for (image, x, y, opacity, anchor) in inputs:
    if not image:
      raise BadRequestError("Each input must include an image")
    if (not isinstance(x, (int, long)) or
        not isinstance(y, (int, long)) or
        not isinstance(opacity, (float))):
      raise TypeError("x_offset, y_offset must be integers and opacity must"
                      "be a float")
    if x > 4000 or x < -4000:
      raise BadRequestError("xOffsets must be in range [-4000, 4000]")
    if y > 4000 or y < -4000:
      raise BadRequestError("yOffsets must be in range [-4000, 4000]")
    if opacity < 0 or opacity > 1:
      raise BadRequestError("Opacity must be in the range 0.0 to 1.0")
    if anchor not in ANCHOR_TYPES:
      raise BadRequestError("Anchor type '%s' not in recognized set %s" %
                            (anchor, ANCHOR_TYPES))
    if image not in image_map:
      image_map[image] = request.image_size()

      if isinstance(image, Image):
        image._set_imagedata(request.add_image())
      else:
        request.add_image().set_content(image)

    option = request.add_options()
    option.set_x_offset(x)
    option.set_y_offset(y)
    option.set_opacity(opacity)
    option.set_anchor(anchor)
    option.set_source_index(image_map[image])

  request.mutable_canvas().mutable_output().set_mime_type(output_encoding)
  request.mutable_canvas().set_width(width)
  request.mutable_canvas().set_height(height)
  request.mutable_canvas().set_color(color)

  if ((output_encoding == JPEG or output_encoding == WEBP) and
      (quality is not None)):
      request.mutable_canvas().mutable_output().set_quality(quality)

  def composite_hook(rpc):
    """Check success, handles exceptions and returns the converted RPC result.

    Args:
      rpc: A UserRPC object.

    Returns:
      Images bytes of the composite image.

    Raises:
      See docstring for composite_async for more details.
    """
    try:
      rpc.check_success()
    except apiproxy_errors.ApplicationError, e:
      raise _ToImagesError(e)
    return rpc.response.image().content()

  return _make_async_call(rpc,
                          "Composite",
                          request,
                          response,
                          composite_hook,
                          None)


def histogram(image_data, rpc=None):
  """Calculates the histogram of the given image.

  Args:
    image_data: str, source image data.
    rpc: An optional UserRPC object.

  Returns: 3 256-element lists containing the number of occurences of each
  value of each color in the order RGB.


  Raises:
    NotImageError when the image data given is not an image.
    BadImageError when the image data given is corrupt.
    LargeImageError when the image data given is too large to process.
    Error when something unknown, but bad, happens.
  """
  rpc = histogram_async(image_data, rpc=rpc)
  return rpc.get_result()


def histogram_async(image_data, rpc=None):
  """Calculates the histogram of the given image - async version.

  Args:
    image_data: str, source image data.
    rpc: An optional UserRPC object.

  Returns:
    An UserRPC object.

  Raises:
    NotImageError when the image data given is not an image.
    BadImageError when the image data given is corrupt.
    LargeImageError when the image data given is too large to process.
    Error when something unknown, but bad, happens.
  """
  image = Image(image_data)
  return image.histogram_async(rpc)


IMG_SERVING_SIZES_LIMIT = 1600


IMG_SERVING_SIZES = [
    32, 48, 64, 72, 80, 90, 94, 104, 110, 120, 128, 144,
    150, 160, 200, 220, 288, 320, 400, 512, 576, 640, 720,
    800, 912, 1024, 1152, 1280, 1440, 1600]


IMG_SERVING_CROP_SIZES = [32, 48, 64, 72, 80, 104, 136, 144, 150, 160]


def get_serving_url(blob_key,
                    size=None,
                    crop=False,
                    secure_url=None,
                    filename=None,
                    rpc=None):
  """Obtain a url that will serve the underlying image.

  This URL is served by a high-performance dynamic image serving infrastructure.
  This URL format also allows dynamic resizing and crop with certain
  restrictions. To get dynamic resizing and cropping, specify size and crop
  arguments, or simply append options to the end of the default url obtained via
  this call.  Here is an example:

  get_serving_url -> "http://lh3.ggpht.com/SomeCharactersGoesHere"

  To get a 32 pixel sized version (aspect-ratio preserved) simply append
  "=s32" to the url:

  "http://lh3.ggpht.com/SomeCharactersGoesHere=s32"

  To get a 32 pixel cropped version simply append "=s32-c":

  "http://lh3.ggpht.com/SomeCharactersGoesHere=s32-c"

  Available sizes are any integer in the range [0, 1600] and is available as
  IMG_SERVING_SIZES_LIMIT.

  Args:
    blob_key: BlobKey, BlobInfo, str, or unicode representation of BlobKey of
      blob to get URL of.
    size: int, size of resulting images
    crop: bool, True requests a cropped image, False a resized one.
    secure_url: bool, True requests a https url, False requests a http url.
    filename: The filename of a Google Storage object to get the URL of.
    rpc: Optional UserRPC object.

  Returns:
    str, a url

  Raises:
    BlobKeyRequiredError: when no blobkey was specified in the ctor.
    UnsupportedSizeError: when size parameters uses unsupported sizes.
    BadRequestError: when crop/size are present in wrong combination, or a
      blob_key and a filename have been specified.
    TypeError: when secure_url is not a boolean type.
    AccessDeniedError: when the blobkey refers to a Google Storage object, and
      the application does not have permission to access the object.
    ObjectNotFoundError:: when the blobkey refers to an object that no longer
      exists.
  """
  rpc = get_serving_url_async(blob_key, size, crop, secure_url, filename, rpc)
  return rpc.get_result()


def get_serving_url_async(blob_key,
                          size=None,
                          crop=False,
                          secure_url=None,
                          filename=None,
                          rpc=None):
  """Obtain a url that will serve the underlying image - async version.

  This URL is served by a high-performance dynamic image serving infrastructure.
  This URL format also allows dynamic resizing and crop with certain
  restrictions. To get dynamic resizing and cropping, specify size and crop
  arguments, or simply append options to the end of the default url obtained via
  this call.  Here is an example:

  get_serving_url -> "http://lh3.ggpht.com/SomeCharactersGoesHere"

  To get a 32 pixel sized version (aspect-ratio preserved) simply append
  "=s32" to the url:

  "http://lh3.ggpht.com/SomeCharactersGoesHere=s32"

  To get a 32 pixel cropped version simply append "=s32-c":

  "http://lh3.ggpht.com/SomeCharactersGoesHere=s32-c"

  Available sizes are any integer in the range [0, 1600] and is available as
  IMG_SERVING_SIZES_LIMIT.

  Args:
    blob_key: BlobKey, BlobInfo, str, or unicode representation of BlobKey of
      blob to get URL of.
    size: int, size of resulting images
    crop: bool, True requests a cropped image, False a resized one.
    secure_url: bool, True requests a https url, False requests a http url.
    filename: The filename of a Google Storage object to get the URL of.
    rpc: Optional UserRPC object.

  Returns:
    A UserRPC whose result will be a string that is the serving url

  Raises:
    BlobKeyRequiredError: when no blobkey was specified in the ctor.
    UnsupportedSizeError: when size parameters uses unsupported sizes.
    BadRequestError: when crop/size are present in wrong combination, or a
      blob_key and a filename have been specified.
    TypeError: when secure_url is not a boolean type.
    AccessDeniedError: when the blobkey refers to a Google Storage object, and
      the application does not have permission to access the object.
  """
  if not blob_key and not filename:
    raise BlobKeyRequiredError(
        "A Blobkey or a filename is required for this operation.")

  if crop and not size:
    raise BadRequestError("Size should be set for crop operation")

  if size is not None and (size > IMG_SERVING_SIZES_LIMIT or size < 0):
    raise UnsupportedSizeError("Unsupported size")

  if secure_url and not isinstance(secure_url, bool):
    raise TypeError("secure_url must be boolean.")

  if filename and blob_key:
    raise BadRequestError("Cannot specify a blob_key and a filename.");

  if filename:
    _blob_key = blobstore.create_gs_key(filename)
    readable_blob_key = filename
  else:
    _blob_key = _extract_blob_key(blob_key)
    readable_blob_key = blob_key

  request = images_service_pb.ImagesGetUrlBaseRequest()
  response = images_service_pb.ImagesGetUrlBaseResponse()

  request.set_blob_key(_blob_key)

  if secure_url:
    request.set_create_secure_url(secure_url)

  def get_serving_url_hook(rpc):
    """Check success, handle exceptions, and return converted RPC result.

    Args:
      rpc: A UserRPC object.

    Returns:
      The URL for serving the image.

    Raises:
      See docstring for get_serving_url for more details.
    """
    try:
      rpc.check_success()
    except apiproxy_errors.ApplicationError, e:
      raise _ToImagesError(e, readable_blob_key)

    url = rpc.response.url()

    if size is not None:
      url += "=s%s" % size
    if crop:
      url += "-c"

    return url

  return _make_async_call(rpc,
                          "GetUrlBase",
                          request,
                          response,
                          get_serving_url_hook,
                          None)


def delete_serving_url(blob_key, rpc=None):
  """Delete a serving url that was created for a blob_key using get_serving_url.

  Args:
    blob_key: BlobKey, BlobInfo, str, or unicode representation of BlobKey of
      blob that has an existing URL to delete.
    rpc: Optional UserRPC object.

  Raises:
    BlobKeyRequiredError: when no blobkey was specified.
    InvalidBlobKeyError: the blob_key supplied was invalid.
    Error: There was a generic error deleting the serving url.
  """
  rpc = delete_serving_url_async(blob_key, rpc)
  rpc.get_result()


def delete_serving_url_async(blob_key, rpc=None):
  """Delete a serving url created using get_serving_url - async version.

  Args:
    blob_key: BlobKey, BlobInfo, str, or unicode representation of BlobKey of
      blob that has an existing URL to delete.
    rpc: Optional UserRPC object.

  Returns:
    A UserRPC object.

  Raises:
    BlobKeyRequiredError: when no blobkey was specified.
    InvalidBlobKeyError: the blob_key supplied was invalid.
    Error: There was a generic error deleting the serving url.
  """
  if not blob_key:
    raise BlobKeyRequiredError("A Blobkey is required for this operation.")

  request = images_service_pb.ImagesDeleteUrlBaseRequest()
  response = images_service_pb.ImagesDeleteUrlBaseResponse()

  request.set_blob_key(_extract_blob_key(blob_key))

  def delete_serving_url_hook(rpc):
    """Checks success, handles exceptions and returns the converted RPC result.

    Args:
      rpc: A UserRPC object.

    Raises:
      See docstring for delete_serving_url_async for more details.
    """
    try:
      rpc.check_success()
    except apiproxy_errors.ApplicationError, e:
      raise _ToImagesError(e, blob_key)

  return _make_async_call(rpc,
                          "DeleteUrlBase",
                          request,
                          response,
                          delete_serving_url_hook,
                          None)


def _extract_blob_key(blob):
  """Extract a unicode blob key from a str, BlobKey, or BlobInfo.

  Args:
    blob: The str, unicode, BlobKey, or BlobInfo that contains the blob key.
  """
  if isinstance(blob, str):
    return blob.decode('utf-8')
  elif isinstance(blob, BlobKey):
    return str(blob).decode('utf-8')
  elif blob.__class__.__name__ == 'BlobInfo':



    return str(blob.key()).decode('utf-8')


  return blob