/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
  9def what(file, h=None):
 10    if h is None:
 11        if isinstance(file, basestring):
 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
 35tests = []
 36
 37def test_jpeg(h, f):
 38    """JPEG data in JFIF format"""
 39    if h[6:10] == 'JFIF':
 40        return 'jpeg'
 41
 42tests.append(test_jpeg)
 43
 44def test_exif(h, f):
 45    """JPEG data in Exif format"""
 46    if h[6:10] == 'Exif':
 47        return 'jpeg'
 48
 49tests.append(test_exif)
 50
 51def test_png(h, f):
 52    if h[:8] == "\211PNG\r\n\032\n":
 53        return 'png'
 54
 55tests.append(test_png)
 56
 57def test_gif(h, f):
 58    """GIF ('87 and '89 variants)"""
 59    if h[:6] in ('GIF87a', 'GIF89a'):
 60        return 'gif'
 61
 62tests.append(test_gif)
 63
 64def test_tiff(h, f):
 65    """TIFF (can be in Motorola or Intel byte order)"""
 66    if h[:2] in ('MM', 'II'):
 67        return 'tiff'
 68
 69tests.append(test_tiff)
 70
 71def test_rgb(h, f):
 72    """SGI image library"""
 73    if h[:2] == '\001\332':
 74        return 'rgb'
 75
 76tests.append(test_rgb)
 77
 78def test_pbm(h, f):
 79    """PBM (portable bitmap)"""
 80    if len(h) >= 3 and \
 81        h[0] == 'P' and h[1] in '14' and h[2] in ' \t\n\r':
 82        return 'pbm'
 83
 84tests.append(test_pbm)
 85
 86def test_pgm(h, f):
 87    """PGM (portable graymap)"""
 88    if len(h) >= 3 and \
 89        h[0] == 'P' and h[1] in '25' and h[2] in ' \t\n\r':
 90        return 'pgm'
 91
 92tests.append(test_pgm)
 93
 94def test_ppm(h, f):
 95    """PPM (portable pixmap)"""
 96    if len(h) >= 3 and \
 97        h[0] == 'P' and h[1] in '36' and h[2] in ' \t\n\r':
 98        return 'ppm'
 99
100tests.append(test_ppm)
101
102def test_rast(h, f):
103    """Sun raster file"""
104    if h[:4] == '\x59\xA6\x6A\x95':
105        return 'rast'
106
107tests.append(test_rast)
108
109def test_xbm(h, f):
110    """X bitmap (X10 or X11)"""
111    s = '#define '
112    if h[:len(s)] == s:
113        return 'xbm'
114
115tests.append(test_xbm)
116
117def test_bmp(h, f):
118    if h[:2] == 'BM':
119        return 'bmp'
120
121tests.append(test_bmp)
122
123#--------------------#
124# Small test program #
125#--------------------#
126
127def 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
142def 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 ***'