"""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 isinstance(file, basestring):
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_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_png(h, f):
if h[:8] == "\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 ('GIF87a', '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 ('MM', 'II'):
return 'tiff'

tests.append(test_tiff)

def test_rgb(h, f):
"""SGI image library"""
if h[:2] == '\001\332':
return 'rgb'

tests.append(test_rgb)

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_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_bmp(h, f):
if h[:2] == '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 + '/:',
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 ***'