"""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_exif(h, f):

    """JPEG data in Exif format"""

    if h[6:10] == 'Exif':

        return 'jpeg'

tests.append(test_exif)

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 ***'