"""Recognize image file formats based on their first few bytes."""__all__ = ["what"]#-------------------------## Recognize image headers ##-------------------------#def what(file, h=None):    if h is None:        if type(file) == type(''):            f = open(file, 'rb')            h = f.read(32)        else:            location = file.tell()            h = file.read(32)            file.seek(location)            f = None    else:        f = None    try:        for tf in tests:            res = tf(h, f)            if res:                return res    finally:        if f: f.close()    return None#---------------------------------## Subroutines per image file type ##---------------------------------#tests = []def test_rgb(h, f):    """SGI image library"""    if h[:2] == '\001\332':        return 'rgb'tests.append(test_rgb)def test_gif(h, f):    """GIF ('87 and '89 variants)"""    if h[:6] in ('GIF87a', 'GIF89a'):        return 'gif'tests.append(test_gif)def test_pbm(h, f):    """PBM (portable bitmap)"""    if len(h) >= 3 and \        h[0] == 'P' and h[1] in '14' and h[2] in ' \t\n\r':        return 'pbm'tests.append(test_pbm)def test_pgm(h, f):    """PGM (portable graymap)"""    if len(h) >= 3 and \        h[0] == 'P' and h[1] in '25' and h[2] in ' \t\n\r':        return 'pgm'tests.append(test_pgm)def test_ppm(h, f):    """PPM (portable pixmap)"""    if len(h) >= 3 and \        h[0] == 'P' and h[1] in '36' and h[2] in ' \t\n\r':        return 'ppm'tests.append(test_ppm)def test_tiff(h, f):    """TIFF (can be in Motorola or Intel byte order)"""    if h[:2] in ('MM', 'II'):        return 'tiff'tests.append(test_tiff)def test_rast(h, f):    """Sun raster file"""    if h[:4] == '\x59\xA6\x6A\x95':        return 'rast'tests.append(test_rast)def test_xbm(h, f):    """X bitmap (X10 or X11)"""    s = '#define '    if h[:len(s)] == s:        return 'xbm'tests.append(test_xbm)def test_jpeg(h, f):    """JPEG data in JFIF format"""    if h[6:10] == 'JFIF':        return 'jpeg'tests.append(test_jpeg)def test_bmp(h, f):    if h[:2] == 'BM':        return 'bmp'tests.append(test_bmp)def test_png(h, f):    if h[:8] == "\211PNG\r\n\032\n":        return 'png'tests.append(test_png)#--------------------## Small test program ##--------------------#def test():    import sys    recursive = 0    if sys.argv[1:] and sys.argv[1] == '-r':        del sys.argv[1:2]        recursive = 1    try:        if sys.argv[1:]:            testall(sys.argv[1:], recursive, 1)        else:            testall(['.'], recursive, 1)    except KeyboardInterrupt:        sys.stderr.write('\n[Interrupted]\n')        sys.exit(1)def testall(list, recursive, toplevel):    import sys    import os    for filename in list:        if os.path.isdir(filename):            print filename + '/:',            if recursive or toplevel:                print 'recursing down:'                import glob                names = glob.glob(os.path.join(filename, '*'))                testall(names, recursive, 0)            else:                print '*** directory (use -r) ***'        else:            print filename + ':',            sys.stdout.flush()            try:                print what(filename)            except IOError:                print '*** not found ***'