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https://github.com/gryf/ebook-converter.git
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Initial import
This commit is contained in:
263
ebook_converter/utils/imghdr.py
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263
ebook_converter/utils/imghdr.py
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#!/usr/bin/env python2
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# vim:fileencoding=utf-8
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# License: GPLv3 Copyright: 2016, Kovid Goyal <kovid at kovidgoyal.net>
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from __future__ import absolute_import, division, print_function, unicode_literals
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from struct import unpack, error
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import os
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from calibre.utils.speedups import ReadOnlyFileBuffer
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from calibre.constants import ispy3
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from polyglot.builtins import string_or_bytes, unicode_type
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""" Recognize image file formats and sizes based on their first few bytes."""
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HSIZE = 120
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def what(file, h=None):
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' Recognize image headers '
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if h is None:
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if isinstance(file, string_or_bytes):
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with lopen(file, 'rb') as f:
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h = f.read(HSIZE)
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else:
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location = file.tell()
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h = file.read(HSIZE)
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file.seek(location)
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if isinstance(h, bytes):
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h = memoryview(h)
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for tf in tests:
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res = tf(h)
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if res:
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return res
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# There exist some jpeg files with no headers, only the starting two bits
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# If we cannot identify as anything else, identify as jpeg.
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if h[:2] == b'\xff\xd8':
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return 'jpeg'
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return None
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def identify(src):
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''' Recognize file format and sizes. Returns format, width, height. width
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and height will be -1 if not found and fmt will be None if the image is not
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recognized. '''
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width = height = -1
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if isinstance(src, unicode_type):
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stream = lopen(src, 'rb')
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elif isinstance(src, bytes):
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stream = ReadOnlyFileBuffer(src)
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else:
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stream = src
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pos = stream.tell()
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head = stream.read(HSIZE)
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stream.seek(pos)
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fmt = what(None, head)
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if fmt in {'jpeg', 'gif', 'png', 'jpeg2000'}:
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size = len(head)
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if fmt == 'png':
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# PNG
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s = head[16:24] if size >= 24 and head[12:16] == b'IHDR' else head[8:16]
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try:
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width, height = unpack(b">LL", s)
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except error:
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return fmt, width, height
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elif fmt == 'jpeg':
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# JPEG
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pos = stream.tell()
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try:
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height, width = jpeg_dimensions(stream)
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except Exception:
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return fmt, width, height
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finally:
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stream.seek(pos)
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elif fmt == 'gif':
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# GIF
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try:
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width, height = unpack(b"<HH", head[6:10])
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except error:
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return fmt, width, height
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elif size >= 56 and fmt == 'jpeg2000':
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# JPEG2000
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try:
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height, width = unpack(b'>LL', head[48:56])
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except error:
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return fmt, width, height
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return fmt, width, height
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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(f):
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tests.append(f)
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return f
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@test
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def jpeg(h):
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"""JPEG data in JFIF format (Changed by Kovid to mimic the file utility,
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the original code was failing with some jpegs that included ICC_PROFILE
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data, for example: http://nationalpostnews.files.wordpress.com/2013/03/budget.jpeg?w=300&h=1571)"""
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if h[6:10] in (b'JFIF', b'Exif'):
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return 'jpeg'
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if h[:2] == b'\xff\xd8':
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q = h[:32].tobytes()
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if b'JFIF' in q or b'8BIM' in q:
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return 'jpeg'
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def jpeg_dimensions(stream):
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# A JPEG marker is two bytes of the form 0xff x where 0 < x < 0xff
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# See section B.1.1.2 of https://www.w3.org/Graphics/JPEG/itu-t81.pdf
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# We read the dimensions from the first SOFn section we come across
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stream.seek(2, os.SEEK_CUR)
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def read(n):
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ans = stream.read(n)
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if len(ans) != n:
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raise ValueError('Truncated JPEG data')
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return ans
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if ispy3:
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def read_byte():
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return read(1)[0]
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else:
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def read_byte():
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return ord(read(1)[0])
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x = None
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while True:
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# Find next marker
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while x != 0xff:
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x = read_byte()
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# Soak up padding
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marker = 0xff
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while marker == 0xff:
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marker = read_byte()
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q = marker
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if 0xc0 <= q <= 0xcf and q != 0xc4 and q != 0xcc:
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# SOFn marker
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stream.seek(3, os.SEEK_CUR)
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return unpack(b'>HH', read(4))
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elif 0xd8 <= q <= 0xda:
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break # start of image, end of image, start of scan, no point
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elif q == 0:
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return -1, -1 # Corrupted JPEG
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elif q == 0x01 or 0xd0 <= q <= 0xd7:
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# Standalone marker
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continue
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else:
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# skip this section
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size = unpack(b'>H', read(2))[0]
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stream.seek(size - 2, os.SEEK_CUR)
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# standalone marker, keep going
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return -1, -1
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@test
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def png(h):
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if h[:8] == b"\211PNG\r\n\032\n":
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return 'png'
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@test
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def gif(h):
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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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@test
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def tiff(h):
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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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if h[2:4] == b'\xbc\x01':
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return 'jxr'
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return 'tiff'
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@test
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def webp(h):
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if h[:4] == b'RIFF' and h[8:12] == b'WEBP':
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return 'webp'
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@test
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def rgb(h):
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"""SGI image library"""
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if h[:2] == b'\001\332':
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return 'rgb'
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@test
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def pbm(h):
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"""PBM (portable bitmap)"""
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if len(h) >= 3 and \
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h[0] == 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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@test
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def pgm(h):
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"""PGM (portable graymap)"""
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if len(h) >= 3 and \
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h[0] == 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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@test
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def ppm(h):
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"""PPM (portable pixmap)"""
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if len(h) >= 3 and \
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h[0] == 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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@test
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def rast(h):
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"""Sun raster file"""
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if h[:4] == b'\x59\xA6\x6A\x95':
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return 'rast'
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@test
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def xbm(h):
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"""X bitmap (X10 or X11)"""
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s = b'#define '
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if h[:len(s)] == s:
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return 'xbm'
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@test
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def bmp(h):
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if h[:2] == b'BM':
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return 'bmp'
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@test
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def emf(h):
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if h[:4] == b'\x01\0\0\0' and h[40:44] == b' EMF':
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return 'emf'
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@test
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def jpeg2000(h):
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if h[:12] == b'\x00\x00\x00\x0cjP \r\n\x87\n':
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return 'jpeg2000'
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@test
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def svg(h):
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if h[:4] == b'<svg' or (h[:2] == b'<?' and h[2:5].tobytes().lower() == b'xml' and b'<svg' in h.tobytes()):
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return 'svg'
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tests = tuple(tests)
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