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

__all__ = ["what"]

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

# Recognize image headers #

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

def what(file, h=None):

f = None

try:

if h is None:

if isinstance(file, str):

f = open(file, 'rb')

h = f.read(32)

else:

location = file.tell()

h = file.read(32)

file.seek(location)

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_jpeg(h, f):

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

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

return 'jpeg'

tests.append(test_jpeg)

def test_png(h, f):

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

return 'png'

tests.append(test_png)

def test_gif(h, f):

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

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

return 'gif'

tests.append(test_gif)

def test_tiff(h, f):

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

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

return 'tiff'

tests.append(test_tiff)

def test_rgb(h, f):

"""SGI image library"""

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

return 'rgb'

tests.append(test_rgb)

def test_pbm(h, f):

"""PBM (portable bitmap)"""

if len(h) >= 3 and \

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

return 'pbm'

tests.append(test_pbm)

def test_pgm(h, f):

"""PGM (portable graymap)"""

if len(h) >= 3 and \

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

return 'pgm'

tests.append(test_pgm)

def test_ppm(h, f):

"""PPM (portable pixmap)"""

if len(h) >= 3 and \

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

return 'ppm'

tests.append(test_ppm)

def test_rast(h, f):

"""Sun raster file"""

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

return 'rast'

tests.append(test_rast)

def test_xbm(h, f):

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

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

return 'xbm'

tests.append(test_xbm)

def test_bmp(h, f):

if h.startswith(b'BM'):

return 'bmp'

tests.append(test_bmp)

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

# 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 + '/:', end=' ')

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 + ':', end=' ')

sys.stdout.flush()

try:

print(what(filename))

except OSError:

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

if __name__ == '__main__':

test()

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