Lib/imghdr.py

   1 # Recognizing image files based on their first few bytes.
   2
   3
   4 #-------------------------#
   5 # Recognize sound headers #
   6 #-------------------------#
   7
   8 def what(filename):
   9         f = open(filename, 'r')
  10         h = f.read(32)
  11         for tf in tests:
  12                 res = tf(h, f)
  13                 if res:
  14                         return res
  15         return None
  16
  17
  18 #---------------------------------#
  19 # Subroutines per image file type #
  20 #---------------------------------#
  21
  22 tests = []
  23
  24 def test_rgb(h, f):
  25         # SGI image library
  26         if h[:2] == '\001\332':
  27                 return 'rgb'
  28
  29 tests.append(test_rgb)
  30
  31 def test_gif(h, f):
  32         # GIF ('87 and '89 variants)
  33         if h[:6] in ('GIF87a', 'GIF89a'):
  34                 return 'gif'
  35
  36 tests.append(test_gif)
  37
  38 def test_pbm(h, f):
  39         # PBM (portable bitmap)
  40         if len(h) >= 3 and \
  41                 h[0] == 'P' and h[1] in '14' and h[2] in ' \t\n\r':
  42                 return 'pbm'
  43
  44 tests.append(test_pbm)
  45
  46 def test_pgm(h, f):
  47         # PGM (portable graymap)
  48         if len(h) >= 3 and \
  49                 h[0] == 'P' and h[1] in '25' and h[2] in ' \t\n\r':
  50                 return 'pgm'
  51
  52 tests.append(test_pgm)
  53
  54 def test_ppm(h, f):
  55         # PPM (portable pixmap)
  56         if len(h) >= 3 and \
  57                 h[0] == 'P' and h[1] in '36' and h[2] in ' \t\n\r':
  58                 return 'ppm'
  59
  60 tests.append(test_ppm)
  61
  62 def test_tiff(h, f):
  63         # TIFF (can be in Motorola or Intel byte order)
  64         if h[:2] in ('MM', 'II'):
  65                 return 'tiff'
  66
  67 tests.append(test_tiff)
  68
  69 def test_rast(h, f):
  70         # Sun raster file
  71         if h[:4] == '\x59\xA6\x6A\x95':
  72                 return 'rast'
  73
  74 tests.append(test_rast)
  75
  76 def test_xbm(h, f):
  77         # X bitmap (X10 or X11)
  78         s = '#define '
  79         if h[:len(s)] == s:
  80                 return 'xbm'
  81
  82 tests.append(test_xbm)
  83
  84 def test_jpeg(h, f):
  85         # JPEG data in JFIF format
  86         if h[6:10] == 'JFIF':
  87                 return 'jpeg'
  88
  89 tests.append(test_jpeg)
  90
  91 #--------------------#
  92 # Small test program #
  93 #--------------------#
  94
  95 def test():
  96         import sys
  97         recursive = 0
  98         if sys.argv[1:] and sys.argv[1] == '-r':
  99                 del sys.argv[1:2]
 100                 recursive = 1
 101         try:
 102                 if sys.argv[1:]:
 103                         testall(sys.argv[1:], recursive, 1)
 104                 else:
 105                         testall(['.'], recursive, 1)
 106         except KeyboardInterrupt:
 107                 sys.stderr.write('\n[Interrupted]\n')
 108                 sys.exit(1)
 109
 110 def testall(list, recursive, toplevel):
 111         import sys
 112         import os
 113         for filename in list:
 114                 if os.path.isdir(filename):
 115                         print filename + '/:',
 116                         if recursive or toplevel:
 117                                 print 'recursing down:'
 118                                 import glob
 119                                 names = glob.glob(os.path.join(filename, '*'))
 120                                 testall(names, recursive, 0)
 121                         else:
 122                                 print '*** directory (use -r) ***'
 123                 else:
 124                         print filename + ':',
 125                         sys.stdout.flush()
 126                         try:
 127                                 print what(filename)
 128                         except IOError:
 129                                 print '*** not found ***'