core/gen/pixeltype.py

   1 # Module with PixelType descrition class
   2 # 2011 - Tomas Gavenciak <gavento@ucw.cz>
   3
   4 # pixel format:
   5 #   type
   6 #   - PAL
   7 #   - HSVRGBA
   8 #   per chan
   9 #     name, pos, size
  10 #   bitwidth
  11 #   name
  12
  13 import re
  14
  15
  16 ## *Global* dictionary of all pixeltypes { name : PixelType }
  17 pixeltypes = {}
  18
  19 ## *Global* set of all encountered channel names
  20 channels = set()
  21
  22 class PixelType(object):
  23   """Representation of one GP_PixelType"""
  24   def __init__(self, name, size, chanslist):
  25     """`name` must be a valid C identifier
  26     `size` is in bits, allowed are 1, 2, 4, 8, 16, 24, 32
  27     `chanslist` is a list of triplets describing individual channels as
  28      [ (`chan_name`, `bit_offset`, `bit_size`) ]
  29      `chan_name` is usually one of: R, G, B, V (value, used for grayscale), A (opacity)
  30     """
  31     assert re.match('\A[A-Za-z][A-Za-z0-9_]*\Z', name)
  32     self.name = name
  33     self.chanslist = chanslist
  34     self.chans = dict() # { chan_name: (offset, size) }
  35     assert(size in [1,2,4,8,16,24,32])
  36     self.size = size
  37     # Numbering from 1 (0 for invalid type)
  38     self.number = min([ptype.number for ptype in pixeltypes.values()] + [0]) + 1
  39
  40     # Verify channel bits for overlaps
  41     # also builds a bit-map of the PixelType
  42     self.bits = ['x']*size
  43     for c in chanslist:
  44       assert c[0] not in self.chans.keys()
  45       self.chans[c[0]] = c
  46       for i in range(c[1],c[1]+c[2]):
  47         assert(i<self.size)
  48         assert(self.bits[i]=='x')
  49         self.bits[i] = c[0]
  50
  51     assert self.name not in pixeltypes.keys()
  52     pixeltypes[self.name] = self
  53     channels.update(set(self.chans.keys()))
  54
  55   def __str__(self):
  56     return "<PixelType " + self.name + ">"