"""Recognize image file formats based on their first few bytes."""
from os import PathLike
__all__ = ["what"]
#-------------------------#
# Recognize image headers #
#-------------------------#
def what(file, h=None):
f = None
try:
if h is None:
if isinstance(file, (str, PathLike)):
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)
def test_webp(h, f):
if h.startswith(b'RIFF') and h[8:12] == b'WEBP':
return 'webp'
tests.append(test_webp)
def test_exr(h, f):
if h.startswith(b'\x76\x2f\x31\x01'):
return 'exr'
tests.append(test_exr)
#--------------------#
# 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()