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Diffstat (limited to 'lib/Python/Lib/PIL/PngImagePlugin.py')
-rw-r--r-- | lib/Python/Lib/PIL/PngImagePlugin.py | 807 |
1 files changed, 807 insertions, 0 deletions
diff --git a/lib/Python/Lib/PIL/PngImagePlugin.py b/lib/Python/Lib/PIL/PngImagePlugin.py new file mode 100644 index 000000000..d8593f90d --- /dev/null +++ b/lib/Python/Lib/PIL/PngImagePlugin.py @@ -0,0 +1,807 @@ +# +# The Python Imaging Library. +# $Id$ +# +# PNG support code +# +# See "PNG (Portable Network Graphics) Specification, version 1.0; +# W3C Recommendation", 1996-10-01, Thomas Boutell (ed.). +# +# history: +# 1996-05-06 fl Created (couldn't resist it) +# 1996-12-14 fl Upgraded, added read and verify support (0.2) +# 1996-12-15 fl Separate PNG stream parser +# 1996-12-29 fl Added write support, added getchunks +# 1996-12-30 fl Eliminated circular references in decoder (0.3) +# 1998-07-12 fl Read/write 16-bit images as mode I (0.4) +# 2001-02-08 fl Added transparency support (from Zircon) (0.5) +# 2001-04-16 fl Don't close data source in "open" method (0.6) +# 2004-02-24 fl Don't even pretend to support interlaced files (0.7) +# 2004-08-31 fl Do basic sanity check on chunk identifiers (0.8) +# 2004-09-20 fl Added PngInfo chunk container +# 2004-12-18 fl Added DPI read support (based on code by Niki Spahiev) +# 2008-08-13 fl Added tRNS support for RGB images +# 2009-03-06 fl Support for preserving ICC profiles (by Florian Hoech) +# 2009-03-08 fl Added zTXT support (from Lowell Alleman) +# 2009-03-29 fl Read interlaced PNG files (from Conrado Porto Lopes Gouvua) +# +# Copyright (c) 1997-2009 by Secret Labs AB +# Copyright (c) 1996 by Fredrik Lundh +# +# See the README file for information on usage and redistribution. +# + +from __future__ import print_function + +__version__ = "0.9" + +import re + +from PIL import Image, ImageFile, ImagePalette, _binary +import zlib + +i8 = _binary.i8 +i16 = _binary.i16be +i32 = _binary.i32be + +is_cid = re.compile(b"\w\w\w\w").match + + +_MAGIC = b"\211PNG\r\n\032\n" + + +_MODES = { + # supported bits/color combinations, and corresponding modes/rawmodes + (1, 0): ("1", "1"), + (2, 0): ("L", "L;2"), + (4, 0): ("L", "L;4"), + (8, 0): ("L", "L"), + (16, 0): ("I", "I;16B"), + (8, 2): ("RGB", "RGB"), + (16, 2): ("RGB", "RGB;16B"), + (1, 3): ("P", "P;1"), + (2, 3): ("P", "P;2"), + (4, 3): ("P", "P;4"), + (8, 3): ("P", "P"), + (8, 4): ("LA", "LA"), + (16, 4): ("RGBA", "LA;16B"), # LA;16B->LA not yet available + (8, 6): ("RGBA", "RGBA"), + (16, 6): ("RGBA", "RGBA;16B"), +} + + +_simple_palette = re.compile(b'^\xff+\x00\xff*$') + +# Maximum decompressed size for a iTXt or zTXt chunk. +# Eliminates decompression bombs where compressed chunks can expand 1000x +MAX_TEXT_CHUNK = ImageFile.SAFEBLOCK +# Set the maximum total text chunk size. +MAX_TEXT_MEMORY = 64 * MAX_TEXT_CHUNK + +def _safe_zlib_decompress(s): + dobj = zlib.decompressobj() + plaintext = dobj.decompress(s, MAX_TEXT_CHUNK) + if dobj.unconsumed_tail: + raise ValueError("Decompressed Data Too Large") + return plaintext + + +# -------------------------------------------------------------------- +# Support classes. Suitable for PNG and related formats like MNG etc. + +class ChunkStream: + + def __init__(self, fp): + + self.fp = fp + self.queue = [] + + if not hasattr(Image.core, "crc32"): + self.crc = self.crc_skip + + def read(self): + "Fetch a new chunk. Returns header information." + + if self.queue: + cid, pos, length = self.queue[-1] + del self.queue[-1] + self.fp.seek(pos) + else: + s = self.fp.read(8) + cid = s[4:] + pos = self.fp.tell() + length = i32(s) + + if not is_cid(cid): + raise SyntaxError("broken PNG file (chunk %s)" % repr(cid)) + + return cid, pos, length + + def close(self): + self.queue = self.crc = self.fp = None + + def push(self, cid, pos, length): + + self.queue.append((cid, pos, length)) + + def call(self, cid, pos, length): + "Call the appropriate chunk handler" + + if Image.DEBUG: + print("STREAM", cid, pos, length) + return getattr(self, "chunk_" + cid.decode('ascii'))(pos, length) + + def crc(self, cid, data): + "Read and verify checksum" + + crc1 = Image.core.crc32(data, Image.core.crc32(cid)) + crc2 = i16(self.fp.read(2)), i16(self.fp.read(2)) + if crc1 != crc2: + raise SyntaxError("broken PNG file" + "(bad header checksum in %s)" % cid) + + def crc_skip(self, cid, data): + "Read checksum. Used if the C module is not present" + + self.fp.read(4) + + def verify(self, endchunk=b"IEND"): + + # Simple approach; just calculate checksum for all remaining + # blocks. Must be called directly after open. + + cids = [] + + while True: + cid, pos, length = self.read() + if cid == endchunk: + break + self.crc(cid, ImageFile._safe_read(self.fp, length)) + cids.append(cid) + + return cids + + +class iTXt(str): + """ + Subclass of string to allow iTXt chunks to look like strings while + keeping their extra information + + """ + @staticmethod + def __new__(cls, text, lang, tkey): + """ + :param value: value for this key + :param lang: language code + :param tkey: UTF-8 version of the key name + """ + + self = str.__new__(cls, text) + self.lang = lang + self.tkey = tkey + return self + + +class PngInfo: + """ + PNG chunk container (for use with save(pnginfo=)) + + """ + + def __init__(self): + self.chunks = [] + + def add(self, cid, data): + """Appends an arbitrary chunk. Use with caution. + + :param cid: a byte string, 4 bytes long. + :param data: a byte string of the encoded data + + """ + + self.chunks.append((cid, data)) + + def add_itxt(self, key, value, lang="", tkey="", zip=False): + """Appends an iTXt chunk. + + :param key: latin-1 encodable text key name + :param value: value for this key + :param lang: language code + :param tkey: UTF-8 version of the key name + :param zip: compression flag + + """ + + if not isinstance(key, bytes): + key = key.encode("latin-1", "strict") + if not isinstance(value, bytes): + value = value.encode("utf-8", "strict") + if not isinstance(lang, bytes): + lang = lang.encode("utf-8", "strict") + if not isinstance(tkey, bytes): + tkey = tkey.encode("utf-8", "strict") + + if zip: + self.add(b"iTXt", key + b"\0\x01\0" + lang + b"\0" + tkey + b"\0" + + zlib.compress(value)) + else: + self.add(b"iTXt", key + b"\0\0\0" + lang + b"\0" + tkey + b"\0" + + value) + + def add_text(self, key, value, zip=0): + """Appends a text chunk. + + :param key: latin-1 encodable text key name + :param value: value for this key, text or an + :py:class:`PIL.PngImagePlugin.iTXt` instance + :param zip: compression flag + + """ + if isinstance(value, iTXt): + return self.add_itxt(key, value, value.lang, value.tkey, bool(zip)) + + # The tEXt chunk stores latin-1 text + if not isinstance(value, bytes): + try: + value = value.encode('latin-1', 'strict') + except UnicodeError: + return self.add_itxt(key, value, zip=bool(zip)) + + if not isinstance(key, bytes): + key = key.encode('latin-1', 'strict') + + if zip: + self.add(b"zTXt", key + b"\0\0" + zlib.compress(value)) + else: + self.add(b"tEXt", key + b"\0" + value) + + +# -------------------------------------------------------------------- +# PNG image stream (IHDR/IEND) + +class PngStream(ChunkStream): + + def __init__(self, fp): + + ChunkStream.__init__(self, fp) + + # local copies of Image attributes + self.im_info = {} + self.im_text = {} + self.im_size = (0, 0) + self.im_mode = None + self.im_tile = None + self.im_palette = None + + self.text_memory = 0 + + def check_text_memory(self, chunklen): + self.text_memory += chunklen + if self.text_memory > MAX_TEXT_MEMORY: + raise ValueError("Too much memory used in text chunks: %s>MAX_TEXT_MEMORY" % + self.text_memory) + + def chunk_iCCP(self, pos, length): + + # ICC profile + s = ImageFile._safe_read(self.fp, length) + # according to PNG spec, the iCCP chunk contains: + # Profile name 1-79 bytes (character string) + # Null separator 1 byte (null character) + # Compression method 1 byte (0) + # Compressed profile n bytes (zlib with deflate compression) + i = s.find(b"\0") + if Image.DEBUG: + print("iCCP profile name", s[:i]) + print("Compression method", i8(s[i])) + comp_method = i8(s[i]) + if comp_method != 0: + raise SyntaxError("Unknown compression method %s in iCCP chunk" % + comp_method) + try: + icc_profile = _safe_zlib_decompress(s[i+2:]) + except zlib.error: + icc_profile = None # FIXME + self.im_info["icc_profile"] = icc_profile + return s + + def chunk_IHDR(self, pos, length): + + # image header + s = ImageFile._safe_read(self.fp, length) + self.im_size = i32(s), i32(s[4:]) + try: + self.im_mode, self.im_rawmode = _MODES[(i8(s[8]), i8(s[9]))] + except: + pass + if i8(s[12]): + self.im_info["interlace"] = 1 + if i8(s[11]): + raise SyntaxError("unknown filter category") + return s + + def chunk_IDAT(self, pos, length): + + # image data + self.im_tile = [("zip", (0, 0)+self.im_size, pos, self.im_rawmode)] + self.im_idat = length + raise EOFError + + def chunk_IEND(self, pos, length): + + # end of PNG image + raise EOFError + + def chunk_PLTE(self, pos, length): + + # palette + s = ImageFile._safe_read(self.fp, length) + if self.im_mode == "P": + self.im_palette = "RGB", s + return s + + def chunk_tRNS(self, pos, length): + + # transparency + s = ImageFile._safe_read(self.fp, length) + if self.im_mode == "P": + if _simple_palette.match(s): + i = s.find(b"\0") + if i >= 0: + self.im_info["transparency"] = i + else: + self.im_info["transparency"] = s + elif self.im_mode == "L": + self.im_info["transparency"] = i16(s) + elif self.im_mode == "RGB": + self.im_info["transparency"] = i16(s), i16(s[2:]), i16(s[4:]) + return s + + def chunk_gAMA(self, pos, length): + + # gamma setting + s = ImageFile._safe_read(self.fp, length) + self.im_info["gamma"] = i32(s) / 100000.0 + return s + + def chunk_pHYs(self, pos, length): + + # pixels per unit + s = ImageFile._safe_read(self.fp, length) + px, py = i32(s), i32(s[4:]) + unit = i8(s[8]) + if unit == 1: # meter + dpi = int(px * 0.0254 + 0.5), int(py * 0.0254 + 0.5) + self.im_info["dpi"] = dpi + elif unit == 0: + self.im_info["aspect"] = px, py + return s + + def chunk_tEXt(self, pos, length): + + # text + s = ImageFile._safe_read(self.fp, length) + try: + k, v = s.split(b"\0", 1) + except ValueError: + # fallback for broken tEXt tags + k = s + v = b"" + if k: + if bytes is not str: + k = k.decode('latin-1', 'strict') + v = v.decode('latin-1', 'replace') + + self.im_info[k] = self.im_text[k] = v + self.check_text_memory(len(v)) + + return s + + def chunk_zTXt(self, pos, length): + + # compressed text + s = ImageFile._safe_read(self.fp, length) + try: + k, v = s.split(b"\0", 1) + except ValueError: + k = s + v = b"" + if v: + comp_method = i8(v[0]) + else: + comp_method = 0 + if comp_method != 0: + raise SyntaxError("Unknown compression method %s in zTXt chunk" % + comp_method) + try: + v = _safe_zlib_decompress(v[1:]) + except zlib.error: + v = b"" + + if k: + if bytes is not str: + k = k.decode('latin-1', 'strict') + v = v.decode('latin-1', 'replace') + + self.im_info[k] = self.im_text[k] = v + self.check_text_memory(len(v)) + + return s + + def chunk_iTXt(self, pos, length): + + # international text + r = s = ImageFile._safe_read(self.fp, length) + try: + k, r = r.split(b"\0", 1) + except ValueError: + return s + if len(r) < 2: + return s + cf, cm, r = i8(r[0]), i8(r[1]), r[2:] + try: + lang, tk, v = r.split(b"\0", 2) + except ValueError: + return s + if cf != 0: + if cm == 0: + try: + v = _safe_zlib_decompress(v) + except zlib.error: + return s + else: + return s + if bytes is not str: + try: + k = k.decode("latin-1", "strict") + lang = lang.decode("utf-8", "strict") + tk = tk.decode("utf-8", "strict") + v = v.decode("utf-8", "strict") + except UnicodeError: + return s + + self.im_info[k] = self.im_text[k] = iTXt(v, lang, tk) + self.check_text_memory(len(v)) + + return s + + +# -------------------------------------------------------------------- +# PNG reader + +def _accept(prefix): + return prefix[:8] == _MAGIC + + +## +# Image plugin for PNG images. + +class PngImageFile(ImageFile.ImageFile): + + format = "PNG" + format_description = "Portable network graphics" + + def _open(self): + + if self.fp.read(8) != _MAGIC: + raise SyntaxError("not a PNG file") + + # + # Parse headers up to the first IDAT chunk + + self.png = PngStream(self.fp) + + while True: + + # + # get next chunk + + cid, pos, length = self.png.read() + + try: + s = self.png.call(cid, pos, length) + except EOFError: + break + except AttributeError: + if Image.DEBUG: + print(cid, pos, length, "(unknown)") + s = ImageFile._safe_read(self.fp, length) + + self.png.crc(cid, s) + + # + # Copy relevant attributes from the PngStream. An alternative + # would be to let the PngStream class modify these attributes + # directly, but that introduces circular references which are + # difficult to break if things go wrong in the decoder... + # (believe me, I've tried ;-) + + self.mode = self.png.im_mode + self.size = self.png.im_size + self.info = self.png.im_info + self.text = self.png.im_text # experimental + self.tile = self.png.im_tile + + if self.png.im_palette: + rawmode, data = self.png.im_palette + self.palette = ImagePalette.raw(rawmode, data) + + self.__idat = length # used by load_read() + + def verify(self): + "Verify PNG file" + + if self.fp is None: + raise RuntimeError("verify must be called directly after open") + + # back up to beginning of IDAT block + self.fp.seek(self.tile[0][2] - 8) + + self.png.verify() + self.png.close() + + self.fp = None + + def load_prepare(self): + "internal: prepare to read PNG file" + + if self.info.get("interlace"): + self.decoderconfig = self.decoderconfig + (1,) + + ImageFile.ImageFile.load_prepare(self) + + def load_read(self, read_bytes): + "internal: read more image data" + + while self.__idat == 0: + # end of chunk, skip forward to next one + + self.fp.read(4) # CRC + + cid, pos, length = self.png.read() + + if cid not in [b"IDAT", b"DDAT"]: + self.png.push(cid, pos, length) + return b"" + + self.__idat = length # empty chunks are allowed + + # read more data from this chunk + if read_bytes <= 0: + read_bytes = self.__idat + else: + read_bytes = min(read_bytes, self.__idat) + + self.__idat = self.__idat - read_bytes + + return self.fp.read(read_bytes) + + def load_end(self): + "internal: finished reading image data" + + self.png.close() + self.png = None + + +# -------------------------------------------------------------------- +# PNG writer + +o8 = _binary.o8 +o16 = _binary.o16be +o32 = _binary.o32be + +_OUTMODES = { + # supported PIL modes, and corresponding rawmodes/bits/color combinations + "1": ("1", b'\x01\x00'), + "L;1": ("L;1", b'\x01\x00'), + "L;2": ("L;2", b'\x02\x00'), + "L;4": ("L;4", b'\x04\x00'), + "L": ("L", b'\x08\x00'), + "LA": ("LA", b'\x08\x04'), + "I": ("I;16B", b'\x10\x00'), + "P;1": ("P;1", b'\x01\x03'), + "P;2": ("P;2", b'\x02\x03'), + "P;4": ("P;4", b'\x04\x03'), + "P": ("P", b'\x08\x03'), + "RGB": ("RGB", b'\x08\x02'), + "RGBA": ("RGBA", b'\x08\x06'), +} + + +def putchunk(fp, cid, *data): + "Write a PNG chunk (including CRC field)" + + data = b"".join(data) + + fp.write(o32(len(data)) + cid) + fp.write(data) + hi, lo = Image.core.crc32(data, Image.core.crc32(cid)) + fp.write(o16(hi) + o16(lo)) + + +class _idat: + # wrap output from the encoder in IDAT chunks + + def __init__(self, fp, chunk): + self.fp = fp + self.chunk = chunk + + def write(self, data): + self.chunk(self.fp, b"IDAT", data) + + +def _save(im, fp, filename, chunk=putchunk, check=0): + # save an image to disk (called by the save method) + + mode = im.mode + + if mode == "P": + + # + # attempt to minimize storage requirements for palette images + if "bits" in im.encoderinfo: + # number of bits specified by user + colors = 1 << im.encoderinfo["bits"] + else: + # check palette contents + if im.palette: + colors = max(min(len(im.palette.getdata()[1])//3, 256), 2) + else: + colors = 256 + + if colors <= 2: + bits = 1 + elif colors <= 4: + bits = 2 + elif colors <= 16: + bits = 4 + else: + bits = 8 + if bits != 8: + mode = "%s;%d" % (mode, bits) + + # encoder options + if "dictionary" in im.encoderinfo: + dictionary = im.encoderinfo["dictionary"] + else: + dictionary = b"" + + im.encoderconfig = ("optimize" in im.encoderinfo, + im.encoderinfo.get("compress_level", -1), + im.encoderinfo.get("compress_type", -1), + dictionary) + + # get the corresponding PNG mode + try: + rawmode, mode = _OUTMODES[mode] + except KeyError: + raise IOError("cannot write mode %s as PNG" % mode) + + if check: + return check + + # + # write minimal PNG file + + fp.write(_MAGIC) + + chunk(fp, b"IHDR", + o32(im.size[0]), o32(im.size[1]), # 0: size + mode, # 8: depth/type + b'\0', # 10: compression + b'\0', # 11: filter category + b'\0') # 12: interlace flag + + if im.mode == "P": + palette_byte_number = (2 ** bits) * 3 + palette_bytes = im.im.getpalette("RGB")[:palette_byte_number] + while len(palette_bytes) < palette_byte_number: + palette_bytes += b'\0' + chunk(fp, b"PLTE", palette_bytes) + + transparency = im.encoderinfo.get('transparency', + im.info.get('transparency', None)) + + if transparency or transparency == 0: + if im.mode == "P": + # limit to actual palette size + alpha_bytes = 2**bits + if isinstance(transparency, bytes): + chunk(fp, b"tRNS", transparency[:alpha_bytes]) + else: + transparency = max(0, min(255, transparency)) + alpha = b'\xFF' * transparency + b'\0' + chunk(fp, b"tRNS", alpha[:alpha_bytes]) + elif im.mode == "L": + transparency = max(0, min(65535, transparency)) + chunk(fp, b"tRNS", o16(transparency)) + elif im.mode == "RGB": + red, green, blue = transparency + chunk(fp, b"tRNS", o16(red) + o16(green) + o16(blue)) + else: + if "transparency" in im.encoderinfo: + # don't bother with transparency if it's an RGBA + # and it's in the info dict. It's probably just stale. + raise IOError("cannot use transparency for this mode") + else: + if im.mode == "P" and im.im.getpalettemode() == "RGBA": + alpha = im.im.getpalette("RGBA", "A") + alpha_bytes = 2**bits + chunk(fp, b"tRNS", alpha[:alpha_bytes]) + + dpi = im.encoderinfo.get("dpi") + if dpi: + chunk(fp, b"pHYs", + o32(int(dpi[0] / 0.0254 + 0.5)), + o32(int(dpi[1] / 0.0254 + 0.5)), + b'\x01') + + info = im.encoderinfo.get("pnginfo") + if info: + for cid, data in info.chunks: + chunk(fp, cid, data) + + # ICC profile writing support -- 2008-06-06 Florian Hoech + if im.info.get("icc_profile"): + # ICC profile + # according to PNG spec, the iCCP chunk contains: + # Profile name 1-79 bytes (character string) + # Null separator 1 byte (null character) + # Compression method 1 byte (0) + # Compressed profile n bytes (zlib with deflate compression) + name = b"ICC Profile" + data = name + b"\0\0" + zlib.compress(im.info["icc_profile"]) + chunk(fp, b"iCCP", data) + + ImageFile._save(im, _idat(fp, chunk), + [("zip", (0, 0)+im.size, 0, rawmode)]) + + chunk(fp, b"IEND", b"") + + try: + fp.flush() + except: + pass + + +# -------------------------------------------------------------------- +# PNG chunk converter + +def getchunks(im, **params): + """Return a list of PNG chunks representing this image.""" + + class collector: + data = [] + + def write(self, data): + pass + + def append(self, chunk): + self.data.append(chunk) + + def append(fp, cid, *data): + data = b"".join(data) + hi, lo = Image.core.crc32(data, Image.core.crc32(cid)) + crc = o16(hi) + o16(lo) + fp.append((cid, data, crc)) + + fp = collector() + + try: + im.encoderinfo = params + _save(im, fp, None, append) + finally: + del im.encoderinfo + + return fp.data + + +# -------------------------------------------------------------------- +# Registry + +Image.register_open("PNG", PngImageFile, _accept) +Image.register_save("PNG", _save) + +Image.register_extension("PNG", ".png") + +Image.register_mime("PNG", "image/png") |