Doc/lib/libimgfile.tex

   1 \section{\module{imgfile} ---
   2          Support for SGI imglib files}
   3
   4 \declaremodule{builtin}{imgfile}
   5   \platform{IRIX}
   6 \modulesynopsis{Support for SGI imglib files.}
   7
   8
   9 The \module{imgfile} module allows Python programs to access SGI imglib image
  10 files (also known as \file{.rgb} files).  The module is far from
  11 complete, but is provided anyway since the functionality that there is
  12 enough in some cases.  Currently, colormap files are not supported.
  13
  14 The module defines the following variables and functions:
  15
  16 \begin{excdesc}{error}
  17 This exception is raised on all errors, such as unsupported file type, etc.
  18 \end{excdesc}
  19
  20 \begin{funcdesc}{getsizes}{file}
  21 This function returns a tuple \code{(\var{x}, \var{y}, \var{z})} where
  22 \var{x} and \var{y} are the size of the image in pixels and
  23 \var{z} is the number of
  24 bytes per pixel. Only 3 byte RGB pixels and 1 byte greyscale pixels
  25 are currently supported.
  26 \end{funcdesc}
  27
  28 \begin{funcdesc}{read}{file}
  29 This function reads and decodes the image on the specified file, and
  30 returns it as a Python string. The string has either 1 byte greyscale
  31 pixels or 4 byte RGBA pixels. The bottom left pixel is the first in
  32 the string. This format is suitable to pass to \function{gl.lrectwrite()},
  33 for instance.
  34 \end{funcdesc}
  35
  36 \begin{funcdesc}{readscaled}{file, x, y, filter\optional{, blur}}
  37 This function is identical to read but it returns an image that is
  38 scaled to the given \var{x} and \var{y} sizes. If the \var{filter} and
  39 \var{blur} parameters are omitted scaling is done by
  40 simply dropping or duplicating pixels, so the result will be less than
  41 perfect, especially for computer-generated images.
  42
  43 Alternatively, you can specify a filter to use to smooth the image
  44 after scaling. The filter forms supported are \code{'impulse'},
  45 \code{'box'}, \code{'triangle'}, \code{'quadratic'} and
  46 \code{'gaussian'}. If a filter is specified \var{blur} is an optional
  47 parameter specifying the blurriness of the filter. It defaults to \code{1.0}.
  48
  49 \function{readscaled()} makes no attempt to keep the aspect ratio
  50 correct, so that is the users' responsibility.
  51 \end{funcdesc}
  52
  53 \begin{funcdesc}{ttob}{flag}
  54 This function sets a global flag which defines whether the scan lines
  55 of the image are read or written from bottom to top (flag is zero,
  56 compatible with SGI GL) or from top to bottom(flag is one,
  57 compatible with X).  The default is zero.
  58 \end{funcdesc}
  59
  60 \begin{funcdesc}{write}{file, data, x, y, z}
  61 This function writes the RGB or greyscale data in \var{data} to image
  62 file \var{file}. \var{x} and \var{y} give the size of the image,
  63 \var{z} is 1 for 1 byte greyscale images or 3 for RGB images (which are
  64 stored as 4 byte values of which only the lower three bytes are used).
  65 These are the formats returned by \function{gl.lrectread()}.
  66 \end{funcdesc}