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 ## Allowed bit-sizes of pixels
  23 bitsizes = [1,2,4,8,16,24,32]
  24
  25 ## bit_endian values
  26 bit_endians = ['LE', 'BE']
  27
  28 ## Create pixel-size suffix (16BPP or 4BPP_LE)
  29 def get_size_suffix(bpp, bit_endian):
  30   assert bpp in bitsizes
  31   assert bit_endian in bit_endians
  32   size_suffix = '%dBPP' % (bpp)
  33   if bpp < 8:
  34     size_suffix += '_' + bit_endian
  35   return size_suffix
  36
  37
  38 class PixelType(object):
  39   """Representation of one GP_PixelType"""
  40   def __init__(self, name, size, chanslist, number=None, bit_endian=None):
  41     """`name` must be a valid C identifier
  42     `size` is in bits, allowed are 1, 2, 4, 8, 16, 24, 32
  43     `bit_endian` is order of 1,2,4BPP pixels in a byte, either 'BE' or 'LE'
  44     `chanslist` is a list of triplets describing individual channels as
  45      [ (`chan_name`, `bit_offset`, `bit_size`) ]
  46      `chan_name` is usually one of: R, G, B, V (value, used for grayscale), A (opacity)
  47      `number` is auto-assigned (internal use only)
  48     """
  49     assert re.match('\A[A-Za-z][A-Za-z0-9_]*\Z', name)
  50     self.name = name
  51     self.chanslist = chanslist
  52     self.chans = dict() # { chan_name: (offset, size) }
  53     # all types except UNKNOWN=0 must have one of these sizes
  54     if number is not 0:
  55       assert(size in bitsizes)
  56     self.size = size
  57
  58     # bit_endian matters only for 1,2,4bpp
  59     if size>=8 and bit_endian is None:
  60       bit_endian = bit_endians[0]
  61     assert bit_endian in bit_endians
  62     self.bit_endian = bit_endian
  63
  64     if self.size == 0:
  65       self.size_suffix = "INVALID"
  66     else:
  67       self.size_suffix = get_size_suffix(self.size, self.bit_endian)
  68
  69     # Numbering from 1
  70     if number is not None:
  71       self.number = number
  72     else:
  73       self.number = max([ptype.number for ptype in pixeltypes.values()] + [0]) + 1
  74
  75     # Verify channel bits for overlaps
  76     # also builds a bit-map of the PixelType
  77     self.bits = ['x']*size
  78     for c in chanslist:
  79       assert c[0] not in self.chans.keys()
  80       self.chans[c[0]] = c
  81       for i in range(c[1],c[1]+c[2]):
  82         assert(i<self.size)
  83         assert(self.bits[i]=='x')
  84         self.bits[i] = c[0]
  85
  86     assert self.name not in pixeltypes.keys()
  87     pixeltypes[self.name] = self
  88     channels.update(set(self.chans.keys()))
  89
  90   def __str__(self):
  91     return "<PixelType " + self.name + ">"
  92
  93 if 0 not in pixeltypes:
  94   PixelType("UNKNOWN", 0, [], bit_endian=bit_endians[0], number=0)