Lib/imghdr.py

   1 # Recognizing image files based on their first few bytes.
   2
   3
   4 #-------------------------#
   5 # Recognize image headers #
   6 #-------------------------#
   7
   8 def what(file, h=None):
   9         if h is None:
  10                 if type(file) == type(''):
  11                         f = open(file, 'rb')
  12                         h = f.read(32)
  13                 else:
  14                         location = file.tell()
  15                         h = file.read(32)
  16                         file.seek(location)
  17                         f = None
  18         else:
  19                 f = None
  20         try:
  21                 for tf in tests:
  22                         res = tf(h, f)
  23                         if res:
  24                                 return res
  25         finally:
  26                 if f: f.close()
  27         return None
  28
  29
  30 #---------------------------------#
  31 # Subroutines per image file type #
  32 #---------------------------------#
  33
  34 tests = []
  35
  36 def test_rgb(h, f):
  37         # SGI image library
  38         if h[:2] == '\001\332':
  39                 return 'rgb'
  40
  41 tests.append(test_rgb)
  42
  43 def test_gif(h, f):
  44         # GIF ('87 and '89 variants)
  45         if h[:6] in ('GIF87a', 'GIF89a'):
  46                 return 'gif'
  47
  48 tests.append(test_gif)
  49
  50 def test_pbm(h, f):
  51         # PBM (portable bitmap)
  52         if len(h) >= 3 and \
  53                 h[0] == 'P' and h[1] in '14' and h[2] in ' \t\n\r':
  54                 return 'pbm'
  55
  56 tests.append(test_pbm)
  57
  58 def test_pgm(h, f):
  59         # PGM (portable graymap)
  60         if len(h) >= 3 and \
  61                 h[0] == 'P' and h[1] in '25' and h[2] in ' \t\n\r':
  62                 return 'pgm'
  63
  64 tests.append(test_pgm)
  65
  66 def test_ppm(h, f):
  67         # PPM (portable pixmap)
  68         if len(h) >= 3 and \
  69                 h[0] == 'P' and h[1] in '36' and h[2] in ' \t\n\r':
  70                 return 'ppm'
  71
  72 tests.append(test_ppm)
  73
  74 def test_tiff(h, f):
  75         # TIFF (can be in Motorola or Intel byte order)
  76         if h[:2] in ('MM', 'II'):
  77                 return 'tiff'
  78
  79 tests.append(test_tiff)
  80
  81 def test_rast(h, f):
  82         # Sun raster file
  83         if h[:4] == '\x59\xA6\x6A\x95':
  84                 return 'rast'
  85
  86 tests.append(test_rast)
  87
  88 def test_xbm(h, f):
  89         # X bitmap (X10 or X11)
  90         s = '#define '
  91         if h[:len(s)] == s:
  92                 return 'xbm'
  93
  94 tests.append(test_xbm)
  95
  96 def test_jpeg(h, f):
  97         # JPEG data in JFIF format
  98         if h[6:10] == 'JFIF':
  99                 return 'jpeg'
 100
 101 tests.append(test_jpeg)
 102
 103 def test_bmp(h, f):
 104         if h[:2] == 'BM':
 105                 return 'bmp'
 106
 107 tests.append(test_bmp)
 108
 109 def test_png(h, f):
 110         if h[:8] == "\211PNG\r\n\032\n":
 111                 return 'png'
 112
 113 tests.append(test_png)
 114
 115 #--------------------#
 116 # Small test program #
 117 #--------------------#
 118
 119 def test():
 120         import sys
 121         recursive = 0
 122         if sys.argv[1:] and sys.argv[1] == '-r':
 123                 del sys.argv[1:2]
 124                 recursive = 1
 125         try:
 126                 if sys.argv[1:]:
 127                         testall(sys.argv[1:], recursive, 1)
 128                 else:
 129                         testall(['.'], recursive, 1)
 130         except KeyboardInterrupt:
 131                 sys.stderr.write('\n[Interrupted]\n')
 132                 sys.exit(1)
 133
 134 def testall(list, recursive, toplevel):
 135         import sys
 136         import os
 137         for filename in list:
 138                 if os.path.isdir(filename):
 139                         print filename + '/:',
 140                         if recursive or toplevel:
 141                                 print 'recursing down:'
 142                                 import glob
 143                                 names = glob.glob(os.path.join(filename, '*'))
 144                                 testall(names, recursive, 0)
 145                         else:
 146                                 print '*** directory (use -r) ***'
 147                 else:
 148                         print filename + ':',
 149                         sys.stdout.flush()
 150                         try:
 151                                 print what(filename)
 152                         except IOError:
 153                                 print '*** not found ***'