"""Recognize image file formats based on their first few bytes."""

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from os import PathLike

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__all__ = ["what"]

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#-------------------------#

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# Recognize image headers #

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#-------------------------#

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def what(file, h=None):

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f = None

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try:

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if h is None:

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if isinstance(file, (str, PathLike)):

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f = open(file, 'rb')

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h = f.read(32)

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else:

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location = file.tell()

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h = file.read(32)

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file.seek(location)

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for tf in tests:

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res = tf(h, f)

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if res:

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return res

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finally:

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if f: f.close()

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return None

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#---------------------------------#

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# Subroutines per image file type #

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#---------------------------------#

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tests = []

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def test_jpeg(h, f):

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"""JPEG data in JFIF or Exif format"""

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if h[6:10] in (b'JFIF', b'Exif'):

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return 'jpeg'

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tests.append(test_jpeg)

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def test_png(h, f):

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if h.startswith(b'\211PNG\r\n\032\n'):

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return 'png'

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tests.append(test_png)

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def test_gif(h, f):

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"""GIF ('87 and '89 variants)"""

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if h[:6] in (b'GIF87a', b'GIF89a'):

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return 'gif'

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tests.append(test_gif)

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def test_tiff(h, f):

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"""TIFF (can be in Motorola or Intel byte order)"""

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if h[:2] in (b'MM', b'II'):

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return 'tiff'

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tests.append(test_tiff)

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def test_rgb(h, f):

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"""SGI image library"""

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if h.startswith(b'\001\332'):

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return 'rgb'

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tests.append(test_rgb)

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def test_pbm(h, f):

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"""PBM (portable bitmap)"""

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if len(h) >= 3 and \

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h[0] == ord(b'P') and h[1] in b'14' and h[2] in b' \t\n\r':

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return 'pbm'

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tests.append(test_pbm)

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def test_pgm(h, f):

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"""PGM (portable graymap)"""

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if len(h) >= 3 and \

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h[0] == ord(b'P') and h[1] in b'25' and h[2] in b' \t\n\r':

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return 'pgm'

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tests.append(test_pgm)

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def test_ppm(h, f):

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"""PPM (portable pixmap)"""

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if len(h) >= 3 and \

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h[0] == ord(b'P') and h[1] in b'36' and h[2] in b' \t\n\r':

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return 'ppm'

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tests.append(test_ppm)

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def test_rast(h, f):

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"""Sun raster file"""

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if h.startswith(b'\x59\xA6\x6A\x95'):

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return 'rast'

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tests.append(test_rast)

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def test_xbm(h, f):

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"""X bitmap (X10 or X11)"""

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if h.startswith(b'#define '):

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return 'xbm'

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tests.append(test_xbm)

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def test_bmp(h, f):

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if h.startswith(b'BM'):

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return 'bmp'

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tests.append(test_bmp)

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def test_webp(h, f):

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if h.startswith(b'RIFF') and h[8:12] == b'WEBP':

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return 'webp'

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tests.append(test_webp)

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def test_exr(h, f):

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if h.startswith(b'\x76\x2f\x31\x01'):

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return 'exr'

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tests.append(test_exr)

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#--------------------#

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# Small test program #

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#--------------------#

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def test():

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import sys

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recursive = 0

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if sys.argv[1:] and sys.argv[1] == '-r':

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del sys.argv[1:2]

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recursive = 1

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try:

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if sys.argv[1:]:

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testall(sys.argv[1:], recursive, 1)

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else:

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testall(['.'], recursive, 1)

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except KeyboardInterrupt:

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sys.stderr.write('\n[Interrupted]\n')

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sys.exit(1)

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def testall(list, recursive, toplevel):

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import sys

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import os

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for filename in list:

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if os.path.isdir(filename):

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print(filename + '/:', end=' ')

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if recursive or toplevel:

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print('recursing down:')

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import glob

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names = glob.glob(os.path.join(filename, '*'))

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testall(names, recursive, 0)

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else:

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print('*** directory (use -r) ***')

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else:

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print(filename + ':', end=' ')

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sys.stdout.flush()

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try:

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print(what(filename))

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except OSError:

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print('*** not found ***')

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if __name__ == '__main__':

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test()

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