Source code for PIL.PngImagePlugin

#
# 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.
#

import itertools
import logging
import re
import struct
import warnings
import zlib

from . import Image, ImageChops, ImageFile, ImagePalette, ImageSequence
from ._binary import i8, i16be as i16, i32be as i32, o8, o16be as o16, o32be as o32

logger = logging.getLogger(__name__)

is_cid = re.compile(br"\w\w\w\w").match


_MAGIC = b"\211PNG\r\n\032\n"


_MODES = {
    # supported bits/color combinations, and corresponding modes/rawmodes
    # Greyscale
    (1, 0): ("1", "1"),
    (2, 0): ("L", "L;2"),
    (4, 0): ("L", "L;4"),
    (8, 0): ("L", "L"),
    (16, 0): ("I", "I;16B"),
    # Truecolour
    (8, 2): ("RGB", "RGB"),
    (16, 2): ("RGB", "RGB;16B"),
    # Indexed-colour
    (1, 3): ("P", "P;1"),
    (2, 3): ("P", "P;2"),
    (4, 3): ("P", "P;4"),
    (8, 3): ("P", "P"),
    # Greyscale with alpha
    (8, 4): ("LA", "LA"),
    (16, 4): ("RGBA", "LA;16B"),  # LA;16B->LA not yet available
    # Truecolour with alpha
    (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


# APNG frame disposal modes
APNG_DISPOSE_OP_NONE = 0
APNG_DISPOSE_OP_BACKGROUND = 1
APNG_DISPOSE_OP_PREVIOUS = 2

# APNG frame blend modes
APNG_BLEND_OP_SOURCE = 0
APNG_BLEND_OP_OVER = 1


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


def _crc32(data, seed=0):
    return zlib.crc32(data, seed) & 0xFFFFFFFF


# --------------------------------------------------------------------
# Support classes.  Suitable for PNG and related formats like MNG etc.


[docs]class ChunkStream: def __init__(self, fp): self.fp = fp self.queue = []
[docs] def read(self): """Fetch a new chunk. Returns header information.""" cid = None if self.queue: cid, pos, length = self.queue.pop() 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): if not ImageFile.LOAD_TRUNCATED_IMAGES: raise SyntaxError("broken PNG file (chunk %s)" % repr(cid)) return cid, pos, length
def __enter__(self): return self def __exit__(self, *args): self.close()
[docs] def close(self): self.queue = self.crc = self.fp = None
[docs] def push(self, cid, pos, length): self.queue.append((cid, pos, length))
[docs] def call(self, cid, pos, length): """Call the appropriate chunk handler""" logger.debug("STREAM %r %s %s", cid, pos, length) return getattr(self, "chunk_" + cid.decode("ascii"))(pos, length)
[docs] def crc(self, cid, data): """Read and verify checksum""" # Skip CRC checks for ancillary chunks if allowed to load truncated # images # 5th byte of first char is 1 [specs, section 5.4] if ImageFile.LOAD_TRUNCATED_IMAGES and (i8(cid[0]) >> 5 & 1): self.crc_skip(cid, data) return try: crc1 = _crc32(data, _crc32(cid)) crc2 = i32(self.fp.read(4)) if crc1 != crc2: raise SyntaxError("broken PNG file (bad header checksum in %r)" % cid) except struct.error: raise SyntaxError("broken PNG file (incomplete checksum in %r)" % cid)
[docs] def crc_skip(self, cid, data): """Read checksum. Used if the C module is not present""" self.fp.read(4)
[docs] def verify(self, endchunk=b"IEND"): # Simple approach; just calculate checksum for all remaining # blocks. Must be called directly after open. cids = [] while True: try: cid, pos, length = self.read() except struct.error: raise OSError("truncated PNG file") if cid == endchunk: break self.crc(cid, ImageFile._safe_read(self.fp, length)) cids.append(cid) return cids
[docs]class iTXt(str): """ Subclass of string to allow iTXt chunks to look like strings while keeping their extra information """
[docs] @staticmethod def __new__(cls, text, lang=None, tkey=None): """ :param cls: the class to use when creating the instance :param text: 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
[docs]class PngInfo: """ PNG chunk container (for use with save(pnginfo=)) """ def __init__(self): self.chunks = []
[docs] 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))
[docs] 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)
[docs] def add_text(self, key, value, zip=False): """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, zip=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=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)
[docs]class PngStream(ChunkStream): def __init__(self, fp): super().__init__(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.im_custom_mimetype = None self.im_n_frames = None self._seq_num = None self.rewind_state = None self.text_memory = 0
[docs] 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 )
[docs] def save_rewind(self): self.rewind_state = { "info": self.im_info.copy(), "tile": self.im_tile, "seq_num": self._seq_num, }
[docs] def rewind(self): self.im_info = self.rewind_state["info"] self.im_tile = self.rewind_state["tile"] self._seq_num = self.rewind_state["seq_num"]
[docs] 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") logger.debug("iCCP profile name %r", s[:i]) logger.debug("Compression method %s", 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 ValueError: if ImageFile.LOAD_TRUNCATED_IMAGES: icc_profile = None else: raise except zlib.error: icc_profile = None # FIXME self.im_info["icc_profile"] = icc_profile return s
[docs] 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 Exception: pass if i8(s[12]): self.im_info["interlace"] = 1 if i8(s[11]): raise SyntaxError("unknown filter category") return s
[docs] def chunk_IDAT(self, pos, length): # image data if "bbox" in self.im_info: tile = [("zip", self.im_info["bbox"], pos, self.im_rawmode)] else: if self.im_n_frames is not None: self.im_info["default_image"] = True tile = [("zip", (0, 0) + self.im_size, pos, self.im_rawmode)] self.im_tile = tile self.im_idat = length raise EOFError
[docs] def chunk_IEND(self, pos, length): # end of PNG image raise EOFError
[docs] 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
[docs] def chunk_tRNS(self, pos, length): # transparency s = ImageFile._safe_read(self.fp, length) if self.im_mode == "P": if _simple_palette.match(s): # tRNS contains only one full-transparent entry, # other entries are full opaque i = s.find(b"\0") if i >= 0: self.im_info["transparency"] = i else: # otherwise, we have a byte string with one alpha value # for each palette entry self.im_info["transparency"] = s elif self.im_mode in ("1", "L", "I"): 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
[docs] 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
[docs] def chunk_cHRM(self, pos, length): # chromaticity, 8 unsigned ints, actual value is scaled by 100,000 # WP x,y, Red x,y, Green x,y Blue x,y s = ImageFile._safe_read(self.fp, length) raw_vals = struct.unpack(">%dI" % (len(s) // 4), s) self.im_info["chromaticity"] = tuple(elt / 100000.0 for elt in raw_vals) return s
[docs] def chunk_sRGB(self, pos, length): # srgb rendering intent, 1 byte # 0 perceptual # 1 relative colorimetric # 2 saturation # 3 absolute colorimetric s = ImageFile._safe_read(self.fp, length) self.im_info["srgb"] = i8(s) return s
[docs] 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
[docs] 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: 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
[docs] 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 ValueError: if ImageFile.LOAD_TRUNCATED_IMAGES: v = b"" else: raise except zlib.error: v = b"" if k: 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
[docs] 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 ValueError: if ImageFile.LOAD_TRUNCATED_IMAGES: return s else: raise except zlib.error: return s else: return s 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
[docs] def chunk_eXIf(self, pos, length): s = ImageFile._safe_read(self.fp, length) self.im_info["exif"] = b"Exif\x00\x00" + s return s
# APNG chunks
[docs] def chunk_acTL(self, pos, length): s = ImageFile._safe_read(self.fp, length) if self.im_n_frames is not None: self.im_n_frames = None warnings.warn("Invalid APNG, will use default PNG image if possible") return s n_frames = i32(s) if n_frames == 0 or n_frames > 0x80000000: warnings.warn("Invalid APNG, will use default PNG image if possible") return s self.im_n_frames = n_frames self.im_info["loop"] = i32(s[4:]) self.im_custom_mimetype = "image/apng" return s
[docs] def chunk_fcTL(self, pos, length): s = ImageFile._safe_read(self.fp, length) seq = i32(s) if (self._seq_num is None and seq != 0) or ( self._seq_num is not None and self._seq_num != seq - 1 ): raise SyntaxError("APNG contains frame sequence errors") self._seq_num = seq width, height = i32(s[4:]), i32(s[8:]) px, py = i32(s[12:]), i32(s[16:]) im_w, im_h = self.im_size if px + width > im_w or py + height > im_h: raise SyntaxError("APNG contains invalid frames") self.im_info["bbox"] = (px, py, px + width, py + height) delay_num, delay_den = i16(s[20:]), i16(s[22:]) if delay_den == 0: delay_den = 100 self.im_info["duration"] = float(delay_num) / float(delay_den) * 1000 self.im_info["disposal"] = i8(s[24]) self.im_info["blend"] = i8(s[25]) return s
[docs] def chunk_fdAT(self, pos, length): s = ImageFile._safe_read(self.fp, 4) seq = i32(s) if self._seq_num != seq - 1: raise SyntaxError("APNG contains frame sequence errors") self._seq_num = seq return self.chunk_IDAT(pos + 4, length - 4)
# -------------------------------------------------------------------- # PNG reader def _accept(prefix): return prefix[:8] == _MAGIC ## # Image plugin for PNG images.
[docs]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") self.__fp = self.fp self.__frame = 0 # # Parse headers up to the first IDAT or fDAT 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: logger.debug("%r %s %s (unknown)", cid, pos, length) 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 = None self.tile = self.png.im_tile self.custom_mimetype = self.png.im_custom_mimetype self._n_frames = self.png.im_n_frames self.default_image = self.info.get("default_image", False) if self.png.im_palette: rawmode, data = self.png.im_palette self.palette = ImagePalette.raw(rawmode, data) if cid == b"fdAT": self.__prepare_idat = length - 4 else: self.__prepare_idat = length # used by load_prepare() if self._n_frames is not None: self._close_exclusive_fp_after_loading = False self.png.save_rewind() self.__rewind_idat = self.__prepare_idat self.__rewind = self.__fp.tell() if self.default_image: # IDAT chunk contains default image and not first animation frame self._n_frames += 1 self._seek(0) @property def text(self): # experimental if self._text is None: # iTxt, tEXt and zTXt chunks may appear at the end of the file # So load the file to ensure that they are read if self.is_animated: frame = self.__frame # for APNG, seek to the final frame before loading self.seek(self.n_frames - 1) self.load() if self.is_animated: self.seek(frame) return self._text @property def n_frames(self): if self._n_frames is None: return 1 return self._n_frames @property def is_animated(self): return self._n_frames is not None and self._n_frames > 1
[docs] 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() if self._exclusive_fp: self.fp.close() self.fp = None
[docs] def seek(self, frame): if not self._seek_check(frame): return if frame < self.__frame: self._seek(0, True) last_frame = self.__frame for f in range(self.__frame + 1, frame + 1): try: self._seek(f) except EOFError: self.seek(last_frame) raise EOFError("no more images in APNG file")
def _seek(self, frame, rewind=False): if frame == 0: if rewind: self.__fp.seek(self.__rewind) self.png.rewind() self.__prepare_idat = self.__rewind_idat self.im = None if self.pyaccess: self.pyaccess = None self.info = self.png.im_info self.tile = self.png.im_tile self.fp = self.__fp self._prev_im = None self.dispose = None self.default_image = self.info.get("default_image", False) self.dispose_op = self.info.get("disposal") self.blend_op = self.info.get("blend") self.dispose_extent = self.info.get("bbox") self.__frame = 0 return else: if frame != self.__frame + 1: raise ValueError("cannot seek to frame %d" % frame) # ensure previous frame was loaded self.load() self.fp = self.__fp # advance to the next frame if self.__prepare_idat: ImageFile._safe_read(self.fp, self.__prepare_idat) self.__prepare_idat = 0 frame_start = False while True: self.fp.read(4) # CRC try: cid, pos, length = self.png.read() except (struct.error, SyntaxError): break if cid == b"IEND": raise EOFError("No more images in APNG file") if cid == b"fcTL": if frame_start: # there must be at least one fdAT chunk between fcTL chunks raise SyntaxError("APNG missing frame data") frame_start = True try: self.png.call(cid, pos, length) except UnicodeDecodeError: break except EOFError: if cid == b"fdAT": length -= 4 if frame_start: self.__prepare_idat = length break ImageFile._safe_read(self.fp, length) except AttributeError: logger.debug("%r %s %s (unknown)", cid, pos, length) ImageFile._safe_read(self.fp, length) self.__frame = frame self.tile = self.png.im_tile self.dispose_op = self.info.get("disposal") self.blend_op = self.info.get("blend") self.dispose_extent = self.info.get("bbox") if not self.tile: raise EOFError
[docs] def tell(self): return self.__frame
[docs] def load_prepare(self): """internal: prepare to read PNG file""" if self.info.get("interlace"): self.decoderconfig = self.decoderconfig + (1,) self.__idat = self.__prepare_idat # used by load_read() ImageFile.ImageFile.load_prepare(self)
[docs] 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", b"fdAT"]: self.png.push(cid, pos, length) return b"" if cid == b"fdAT": try: self.png.call(cid, pos, length) except EOFError: pass self.__idat = length - 4 # sequence_num has already been read else: 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)
[docs] def load_end(self): """internal: finished reading image data""" while True: self.fp.read(4) # CRC try: cid, pos, length = self.png.read() except (struct.error, SyntaxError): break if cid == b"IEND": break elif cid == b"fcTL" and self.is_animated: # start of the next frame, stop reading self.__prepare_idat = 0 self.png.push(cid, pos, length) break try: self.png.call(cid, pos, length) except UnicodeDecodeError: break except EOFError: if cid == b"fdAT": length -= 4 ImageFile._safe_read(self.fp, length) except AttributeError: logger.debug("%r %s %s (unknown)", cid, pos, length) ImageFile._safe_read(self.fp, length) self._text = self.png.im_text if not self.is_animated: self.png.close() self.png = None else: # setup frame disposal (actual disposal done when needed in _seek()) if self._prev_im is None and self.dispose_op == APNG_DISPOSE_OP_PREVIOUS: self.dispose_op = APNG_DISPOSE_OP_BACKGROUND if self.dispose_op == APNG_DISPOSE_OP_PREVIOUS: dispose = self._prev_im.copy() dispose = self._crop(dispose, self.dispose_extent) elif self.dispose_op == APNG_DISPOSE_OP_BACKGROUND: dispose = Image.core.fill("RGBA", self.size, (0, 0, 0, 0)) dispose = self._crop(dispose, self.dispose_extent) else: dispose = None if self._prev_im and self.blend_op == APNG_BLEND_OP_OVER: updated = self._crop(self.im, self.dispose_extent) self._prev_im.paste( updated, self.dispose_extent, updated.convert("RGBA") ) self.im = self._prev_im if self.pyaccess: self.pyaccess = None self._prev_im = self.im.copy() if dispose: self._prev_im.paste(dispose, self.dispose_extent)
def _getexif(self): if "exif" not in self.info: self.load() if "exif" not in self.info and "Raw profile type exif" not in self.info: return None return dict(self.getexif())
[docs] def getexif(self): if "exif" not in self.info: self.load() if self._exif is None: self._exif = Image.Exif() exif_info = self.info.get("exif") if exif_info is None and "Raw profile type exif" in self.info: exif_info = bytes.fromhex( "".join(self.info["Raw profile type exif"].split("\n")[3:]) ) self._exif.load(exif_info) return self._exif
def _close__fp(self): try: if self.__fp != self.fp: self.__fp.close() except AttributeError: pass finally: self.__fp = None
# -------------------------------------------------------------------- # PNG writer _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"), "I;16": ("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"), }
[docs]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) crc = _crc32(data, _crc32(cid)) fp.write(o32(crc))
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) class _fdat: # wrap encoder output in fdAT chunks def __init__(self, fp, chunk, seq_num): self.fp = fp self.chunk = chunk self.seq_num = seq_num def write(self, data): self.chunk(self.fp, b"fdAT", o32(self.seq_num), data) self.seq_num += 1 def _write_multiple_frames(im, fp, chunk, rawmode): default_image = im.encoderinfo.get("default_image", im.info.get("default_image")) duration = im.encoderinfo.get("duration", im.info.get("duration", 0)) loop = im.encoderinfo.get("loop", im.info.get("loop", 0)) disposal = im.encoderinfo.get("disposal", im.info.get("disposal")) blend = im.encoderinfo.get("blend", im.info.get("blend")) if default_image: chain = itertools.chain(im.encoderinfo.get("append_images", [])) else: chain = itertools.chain([im], im.encoderinfo.get("append_images", [])) im_frames = [] frame_count = 0 for im_seq in chain: for im_frame in ImageSequence.Iterator(im_seq): im_frame = im_frame.copy() if im_frame.mode != im.mode: if im.mode == "P": im_frame = im_frame.convert(im.mode, palette=im.palette) else: im_frame = im_frame.convert(im.mode) encoderinfo = im.encoderinfo.copy() if isinstance(duration, (list, tuple)): encoderinfo["duration"] = duration[frame_count] if isinstance(disposal, (list, tuple)): encoderinfo["disposal"] = disposal[frame_count] if isinstance(blend, (list, tuple)): encoderinfo["blend"] = blend[frame_count] frame_count += 1 if im_frames: previous = im_frames[-1] prev_disposal = previous["encoderinfo"].get("disposal") prev_blend = previous["encoderinfo"].get("blend") if prev_disposal == APNG_DISPOSE_OP_PREVIOUS and len(im_frames) < 2: prev_disposal == APNG_DISPOSE_OP_BACKGROUND if prev_disposal == APNG_DISPOSE_OP_BACKGROUND: base_im = previous["im"] dispose = Image.core.fill("RGBA", im.size, (0, 0, 0, 0)) bbox = previous["bbox"] if bbox: dispose = dispose.crop(bbox) else: bbox = (0, 0) + im.size base_im.paste(dispose, bbox) elif prev_disposal == APNG_DISPOSE_OP_PREVIOUS: base_im = im_frames[-2]["im"] else: base_im = previous["im"] delta = ImageChops.subtract_modulo( im_frame.convert("RGB"), base_im.convert("RGB") ) bbox = delta.getbbox() if ( not bbox and prev_disposal == encoderinfo.get("disposal") and prev_blend == encoderinfo.get("blend") ): duration = encoderinfo.get("duration", 0) if duration: if "duration" in previous["encoderinfo"]: previous["encoderinfo"]["duration"] += duration else: previous["encoderinfo"]["duration"] = duration continue else: bbox = None im_frames.append({"im": im_frame, "bbox": bbox, "encoderinfo": encoderinfo}) # animation control chunk( fp, b"acTL", o32(len(im_frames)), o32(loop), # 0: num_frames # 4: num_plays ) # default image IDAT (if it exists) if default_image: ImageFile._save(im, _idat(fp, chunk), [("zip", (0, 0) + im.size, 0, rawmode)]) seq_num = 0 for frame, frame_data in enumerate(im_frames): im_frame = frame_data["im"] if not frame_data["bbox"]: bbox = (0, 0) + im_frame.size else: bbox = frame_data["bbox"] im_frame = im_frame.crop(bbox) size = im_frame.size duration = int(round(frame_data["encoderinfo"].get("duration", 0))) disposal = frame_data["encoderinfo"].get("disposal", APNG_DISPOSE_OP_NONE) blend = frame_data["encoderinfo"].get("blend", APNG_BLEND_OP_SOURCE) # frame control chunk( fp, b"fcTL", o32(seq_num), # sequence_number o32(size[0]), # width o32(size[1]), # height o32(bbox[0]), # x_offset o32(bbox[1]), # y_offset o16(duration), # delay_numerator o16(1000), # delay_denominator o8(disposal), # dispose_op o8(blend), # blend_op ) seq_num += 1 # frame data if frame == 0 and not default_image: # first frame must be in IDAT chunks for backwards compatibility ImageFile._save( im_frame, _idat(fp, chunk), [("zip", (0, 0) + im_frame.size, 0, rawmode)], ) else: fdat_chunks = _fdat(fp, chunk, seq_num) ImageFile._save( im_frame, fdat_chunks, [("zip", (0, 0) + im_frame.size, 0, rawmode)], ) seq_num = fdat_chunks.seq_num def _save_all(im, fp, filename): _save(im, fp, filename, save_all=True) def _save(im, fp, filename, chunk=putchunk, save_all=False): # 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 im.encoderconfig = ( im.encoderinfo.get("optimize", False), im.encoderinfo.get("compress_level", -1), im.encoderinfo.get("compress_type", -1), im.encoderinfo.get("dictionary", b""), ) # get the corresponding PNG mode try: rawmode, mode = _OUTMODES[mode] except KeyError: raise OSError("cannot write mode %s as PNG" % mode) # # write minimal PNG file fp.write(_MAGIC) chunk( fp, b"IHDR", o32(im.size[0]), # 0: size o32(im.size[1]), mode, # 8: depth/type b"\0", # 10: compression b"\0", # 11: filter category b"\0", # 12: interlace flag ) chunks = [b"cHRM", b"gAMA", b"sBIT", b"sRGB", b"tIME"] icc = im.encoderinfo.get("icc_profile", im.info.get("icc_profile")) if icc: # 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(icc) chunk(fp, b"iCCP", data) # You must either have sRGB or iCCP. # Disallow sRGB chunks when an iCCP-chunk has been emitted. chunks.remove(b"sRGB") info = im.encoderinfo.get("pnginfo") if info: chunks_multiple_allowed = [b"sPLT", b"iTXt", b"tEXt", b"zTXt"] for cid, data in info.chunks: if cid in chunks: chunks.remove(cid) chunk(fp, cid, data) elif cid in chunks_multiple_allowed: chunk(fp, cid, data) 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 in ("1", "L", "I"): 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 OSError("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", ) if info: chunks = [b"bKGD", b"hIST"] for cid, data in info.chunks: if cid in chunks: chunks.remove(cid) chunk(fp, cid, data) exif = im.encoderinfo.get("exif", im.info.get("exif")) if exif: if isinstance(exif, Image.Exif): exif = exif.tobytes(8) if exif.startswith(b"Exif\x00\x00"): exif = exif[6:] chunk(fp, b"eXIf", exif) if save_all: _write_multiple_frames(im, fp, chunk, rawmode) else: ImageFile._save(im, _idat(fp, chunk), [("zip", (0, 0) + im.size, 0, rawmode)]) chunk(fp, b"IEND", b"") if hasattr(fp, "flush"): fp.flush() # -------------------------------------------------------------------- # PNG chunk converter
[docs]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) crc = o32(_crc32(data, _crc32(cid))) 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(PngImageFile.format, PngImageFile, _accept) Image.register_save(PngImageFile.format, _save) Image.register_save_all(PngImageFile.format, _save_all) Image.register_extensions(PngImageFile.format, [".png", ".apng"]) Image.register_mime(PngImageFile.format, "image/png")