pylib/gfxprim/generators/pixeltype.py

   1 #
   2 #  gfxprim.pixeltype - Module with PixelType descrition class
   3 #
   4 # 2011 - Tomas Gavenciak <gavento@ucw.cz>
   5 #
   6
   7 import re
   8 import os
   9 import sys
  10 import gfxprim
  11 from gfxprim import die
  12
  13
  14 def get_size_suffix(self.bpp, bit_endian):
  15   "Create pixel-size suffix (like 16BPP or 4BPP_LE)"
  16
  17   assert bpp in self.sizes
  18   assert bit_endian in self.bit_endians
  19   size_suffix = '%dBPP' % (bpp)
  20   if bpp < 8:
  21     size_suffix += '_' + bit_endian
  22   return size_suffix
  23
  24
  25 class PixelType(object):
  26   """Representation of one GP_PixelType"""
  27
  28   def __init__(self, name, size, chanslist, bit_endian=None):
  29     """`name` must be a valid C identifier
  30     `size` is type bit-width
  31     `bit_endian` is required in 1,2,4 BPP types to determine the order of
  32        pixels in a byte, either 'BE' or 'LE'
  33     `chanslist` is a list of triplets describing individual channels as
  34       [ (`chan_name`, `bit_offset`, `bit_size`) ]
  35       where `chan_name` is usually one of: R, G, B,
  36       V (value, used for grayscale), A (opacity)
  37     """
  38     assert re.match('\A[A-Za-z][A-Za-z0-9_]*\Z', name)
  39     self.name = name
  40     self.chanslist = chanslist
  41     self.chans = dict() # { chan_name: (offset, size) }
  42     self.size = size
  43     self.bit_endian = bit_endian
  44
  45     if self.size == 0:
  46       self.size_suffix = "INVALID"
  47     else:
  48       self.size_suffix = get_size_suffix(self.size, self.bit_endian)
  49
  50     # Verify channel bits for overlaps
  51     # also builds a bit-map of the PixelType
  52     self.bits = ['x']*size
  53     for c in chanslist:
  54       assert c[0] not in self.chans.keys()
  55       self.chans[c[0]] = c
  56       for i in range(c[1],c[1]+c[2]):
  57         assert(i<self.size)
  58         assert(self.bits[i]=='x')
  59         self.bits[i] = c[0]
  60
  61   def valid_for_config(self, config):
  62     "Check PixelType compatibility with given GfxPrimConfig."
  63
  64     # all types except UNKNOWN=0 must have one of these sizes
  65     if self.name != "UNKNOWN":
  66       assert(self.size in config.sizes)
  67
  68     # bit_endian matters only for non-multiple-of-8 bpp
  69     if size % 8 != 0 or bit_endian is not None:
  70       assert bit_endian in config.bit_endians
  71
  72   def __str__(self):
  73     return "<PixelType " + self.name + ">"
  74
  75   def is_palette(self):
  76     return ('P' in self.chans)
  77