Lib/imghdr.py

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