class __GIF__(ImageMetrics):
HEADER = construct.Struct('header',
construct.Const(construct.String('gif',3),'GIF'),
construct.String('version',3))
SCREEN_DESCRIPTOR = construct.Struct('logical_screen_descriptor',
construct.ULInt16('width'),
construct.ULInt16('height'),
construct.Embed(
construct.BitStruct('packed_fields',
construct.Flag('global_color_table'),
construct.Bits('color_resolution',3),
construct.Flag('sort'),
construct.Bits('global_color_table_size',3))),
construct.Byte('background_color_index'),
construct.Byte('pixel_aspect_ratio'))
def __init__(self, width, height, color_count):
ImageMetrics.__init__(self, width, height, 8, color_count, u'image/gif')
@classmethod
def parse(cls, file):
try:
header = cls.HEADER.parse_stream(file)
descriptor = cls.SCREEN_DESCRIPTOR.parse_stream(file)
return __GIF__(descriptor.width, descriptor.height,
2 ** (descriptor.global_color_table_size + 1))
except construct.ConstError:
raise InvalidGIF(_(u'Invalid GIF'))
class __BMP__(ImageMetrics):
HEADER = construct.Struct('bmp_header',
construct.Const(construct.String('magic_number',2),'BM'),
construct.ULInt32('file_size'),
construct.ULInt16('reserved1'),
construct.ULInt16('reserved2'),
construct.ULInt32('bitmap_data_offset'))
INFORMATION = construct.Struct('bmp_information',
construct.ULInt32('header_size'),
construct.ULInt32('width'),
construct.ULInt32('height'),
construct.ULInt16('color_planes'),
construct.ULInt16('bits_per_pixel'),
construct.ULInt32('compression_method'),
construct.ULInt32('image_size'),
construct.ULInt32('horizontal_resolution'),
construct.ULInt32('vertical_resolution'),
construct.ULInt32('colors_used'),
construct.ULInt32('important_colors_used'))
def __init__(self, width, height, bits_per_pixel, color_count):
ImageMetrics.__init__(self, width, height, bits_per_pixel, color_count,
u'image/x-ms-bmp')
@classmethod
def parse(cls, file):
try:
header = cls.HEADER.parse_stream(file)
information = cls.INFORMATION.parse_stream(file)
return __BMP__(information.width, information.height,
information.bits_per_pixel,
information.colors_used)
except construct.ConstError:
raise InvalidBMP(_(u'Invalid BMP'))
def l_tag_value(cls, file, tag):
subtype = {1:construct.Byte("data"),
2:construct.CString("data"),
3:construct.ULInt16("data"),
4:construct.ULInt32("data"),
5:construct.Struct("data",
construct.ULInt32("high"),
construct.ULInt32("low"))}[tag.type]
data = construct.StrictRepeater(tag.count,
subtype)
if ((tag.type != 2) and (data.sizeof() <= 4)):
return tag.offset
else:
file.seek(tag.offset,0)
return data.parse_stream(file)
class __JPEG__(ImageMetrics):
SEGMENT_HEADER = construct.Struct('segment_header',
construct.Const(construct.Byte('header'),0xFF),
construct.Byte('type'),
construct.If(
lambda ctx: ctx['type'] not in (0xD8,0xD9),
construct.UBInt16('length')))
APP0 = construct.Struct('JFIF_segment_marker',
construct.String('identifier',5),
construct.Byte('major_version'),
construct.Byte('minor_version'),
construct.Byte('density_units'),
construct.UBInt16('x_density'),
construct.UBInt16('y_density'),
construct.Byte('thumbnail_width'),
construct.Byte('thumbnail_height'))
SOF = construct.Struct('start_of_frame',
construct.Byte('data_precision'),
construct.UBInt16('image_height'),
construct.UBInt16('image_width'),
construct.Byte('components'))
def __init__(self, width, height, bits_per_pixel):
ImageMetrics.__init__(self, width, height, bits_per_pixel,
0, u'image/jpeg')
@classmethod
def parse(cls, file):
try:
header = cls.SEGMENT_HEADER.parse_stream(file)
if (header.type != 0xD8):
raise InvalidJPEG(_(u'Invalid JPEG header'))
segment = cls.SEGMENT_HEADER.parse_stream(file)
while (segment.type != 0xD9):
if (segment.type == 0xDA):
break
if (segment.type in (0xC0,0xC1,0xC2,0xC3,
0xC5,0XC5,0xC6,0xC7,
0xC9,0xCA,0xCB,0xCD,
0xCE,0xCF)): #start of frame
segment_data = cStringIO.StringIO(
file.read(segment.length - 2))
frame0 = cls.SOF.parse_stream(segment_data)
segment_data.close()
return __JPEG__(width = frame0.image_width,
height = frame0.image_height,
bits_per_pixel = (frame0.data_precision * \
frame0.components))
else:
file.seek(segment.length - 2,1)
segment = cls.SEGMENT_HEADER.parse_stream(file)
raise InvalidJPEG(_(u'Start of frame not found'))
except construct.ConstError:
raise InvalidJPEG(_(u"Invalid JPEG segment marker at 0x%X") % \
(file.tell()))
class __TIFF__(ImageMetrics):
HEADER = construct.Struct('header',
construct.String('byte_order',2),
construct.Switch('order',
lambda ctx: ctx['byte_order'],
{"II":construct.Embed(
construct.Struct('little_endian',
construct.Const(construct.ULInt16('version'),42),
construct.ULInt32('offset'))),
"MM":construct.Embed(
construct.Struct('big_endian',
construct.Const(construct.UBInt16('version'),42),
construct.UBInt32('offset')))}))
L_IFD = construct.Struct('ifd',
construct.PrefixedArray(
length_field=construct.ULInt16('length'),
subcon=construct.Struct('tags',
construct.ULInt16('id'),
construct.ULInt16('type'),
construct.ULInt32('count'),
construct.ULInt32('offset'))),
construct.ULInt32('next'))
B_IFD = construct.Struct('ifd',
construct.PrefixedArray(
length_field=construct.UBInt16('length'),
subcon=construct.Struct('tags',
construct.UBInt16('id'),
construct.UBInt16('type'),
construct.UBInt32('count'),
construct.UBInt32('offset'))),
construct.UBInt32('next'))
def __init__(self, width, height, bits_per_pixel, color_count):
ImageMetrics.__init__(self, width, height,
bits_per_pixel, color_count,
u'image/tiff')
@classmethod
def b_tag_value(cls, file, tag):
subtype = {1:construct.Byte("data"),
2:construct.CString("data"),
3:construct.UBInt16("data"),
4:construct.UBInt32("data"),
5:construct.Struct("data",
construct.UBInt32("high"),
construct.UBInt32("low"))}[tag.type]
data = construct.StrictRepeater(tag.count,
subtype)
if ((tag.type != 2) and (data.sizeof() <= 4)):
return tag.offset
else:
file.seek(tag.offset,0)
return data.parse_stream(file)
@classmethod
def l_tag_value(cls, file, tag):
subtype = {1:construct.Byte("data"),
2:construct.CString("data"),
3:construct.ULInt16("data"),
4:construct.ULInt32("data"),
5:construct.Struct("data",
construct.ULInt32("high"),
construct.ULInt32("low"))}[tag.type]
data = construct.StrictRepeater(tag.count,
subtype)
if ((tag.type != 2) and (data.sizeof() <= 4)):
return tag.offset
else:
file.seek(tag.offset,0)
return data.parse_stream(file)
@classmethod
def parse(cls, file):
width = 0
height = 0
bits_per_sample = 0
color_count = 0
try:
header = cls.HEADER.parse_stream(file)
if (header.byte_order == 'II'):
IFD = cls.L_IFD
tag_value = cls.l_tag_value
elif (header.byte_order == 'MM'):
IFD = cls.B_IFD
tag_value = cls.b_tag_value
else:
raise InvalidTIFF(_(u'Invalid byte order'))
file.seek(header.offset,0)
ifd = IFD.parse_stream(file)
while (True):
for tag in ifd.tags:
if (tag.id == 0x0100):
width = tag_value(file,tag)
elif (tag.id == 0x0101):
height = tag_value(file,tag)
elif (tag.id == 0x0102):
try:
bits_per_sample = sum(tag_value(file,tag))
except TypeError:
bits_per_sample = tag_value(file,tag)
elif (tag.id == 0x0140):
color_count = tag.count / 3
else:
pass
if (ifd.next == 0x00):
break
else:
file.seek(ifd.next,0)
ifd = IFD.parse_stream(file)
return __TIFF__(width,height,bits_per_sample,color_count)
except construct.ConstError:
raise InvalidTIFF(_(u'Invalid TIFF'))
class __PNG__(ImageMetrics):
HEADER = construct.Const(construct.String('header',8),
'89504e470d0a1a0a'.decode('hex'))
CHUNK_HEADER = construct.Struct('chunk',
construct.UBInt32('length'),
construct.String('type',4))
CHUNK_FOOTER = construct.Struct('crc32',
construct.UBInt32('crc'))
IHDR = construct.Struct('IHDR',
construct.UBInt32('width'),
construct.UBInt32('height'),
construct.Byte('bit_depth'),
construct.Byte('color_type'),
construct.Byte('compression_method'),
construct.Byte('filter_method'),
construct.Byte('interlace_method'))
def __init__(self, width, height, bits_per_pixel, color_count):
ImageMetrics.__init__(self, width, height, bits_per_pixel, color_count,
u'image/png')
@classmethod
def parse(cls, file):
ihdr = None
plte = None
try:
header = cls.HEADER.parse_stream(file)
chunk_header = cls.CHUNK_HEADER.parse_stream(file)
data = file.read(chunk_header.length)
chunk_footer = cls.CHUNK_FOOTER.parse_stream(file)
while (chunk_header.type != 'IEND'):
if (chunk_header.type == 'IHDR'):
ihdr = cls.IHDR.parse(data)
elif (chunk_header.type == 'PLTE'):
plte = data
chunk_header = cls.CHUNK_HEADER.parse_stream(file)
data = file.read(chunk_header.length)
chunk_footer = cls.CHUNK_FOOTER.parse_stream(file)
if (ihdr.color_type == 0): #grayscale
bits_per_pixel = ihdr.bit_depth
color_count = 0
elif (ihdr.color_type == 2): #RGB
bits_per_pixel = ihdr.bit_depth * 3
color_count = 0
elif (ihdr.color_type == 3): #palette
bits_per_pixel = 8
if ((len(plte) % 3) != 0):
raise InvalidPNG(_(u'Invalid PLTE chunk length'))
else:
color_count = len(plte) / 3
elif (ihdr.color_type == 4): #grayscale + alpha
bits_per_pixel = ihdr.bit_depth * 2
color_count = 0
elif (ihdr.color_type == 6): #RGB + alpha
bits_per_pixel = ihdr.bit_depth * 4
color_count = 0
return __PNG__(ihdr.width,ihdr.height,bits_per_pixel,color_count)
except construct.ConstError:
raise InvalidPNG(_(u'Invalid PNG'))