bmp.py

   1 # bmp - bitmap processing
   2
   3 from struct import unpack
   4
   5 class FormatError(Exception): pass
   6 class MagicError(FileFormatError): pass
   7 class CompressionError(FormatError): pass
   8 class BppError(FormatError): pass
   9
  10 class Bmp(object):
  11         def __init__(self, fn_or_fo):
  12                 fo = fn_or_fo
  13                 if isinstance(fn_or_fo, basestring):
  14                         fo = open(fn, 'rb')
  15                 self.fo = fo
  16                 self._read()
  17         def _read(self):
  18                 header = self.fo.read(14)
  19                 magic, filesize, start_address = unpack("<2sI2x2xI", header)
  20                 if magic != "BM": raise MagicError("wrong BMP header magic")
  21                 dib = self.fo.read(40)
  22                 magic, pixelwidth, pixelheight, bpp, compression = unpack("<III2xHI4x4x4x4x4x", dib)
  23                 if magic != 40: raise MagicError("wrong DIB header magic")
  24                 if compression != 0: raise CompressionError("compression not supported")