238 lines
6.2 KiB
Python
238 lines
6.2 KiB
Python
#
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# The Python Imaging Library.
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# $Id$
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#
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# SGI image file handling
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#
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# See "The SGI Image File Format (Draft version 0.97)", Paul Haeberli.
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# <ftp://ftp.sgi.com/graphics/SGIIMAGESPEC>
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#
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#
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# History:
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# 2017-22-07 mb Add RLE decompression
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# 2016-16-10 mb Add save method without compression
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# 1995-09-10 fl Created
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#
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# Copyright (c) 2016 by Mickael Bonfill.
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# Copyright (c) 2008 by Karsten Hiddemann.
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# Copyright (c) 1997 by Secret Labs AB.
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# Copyright (c) 1995 by Fredrik Lundh.
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#
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# See the README file for information on usage and redistribution.
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#
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from __future__ import annotations
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import os
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import struct
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from typing import IO
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from . import Image, ImageFile
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from ._binary import i16be as i16
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from ._binary import o8
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def _accept(prefix: bytes) -> bool:
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return len(prefix) >= 2 and i16(prefix) == 474
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MODES = {
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(1, 1, 1): "L",
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(1, 2, 1): "L",
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(2, 1, 1): "L;16B",
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(2, 2, 1): "L;16B",
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(1, 3, 3): "RGB",
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(2, 3, 3): "RGB;16B",
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(1, 3, 4): "RGBA",
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(2, 3, 4): "RGBA;16B",
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}
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##
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# Image plugin for SGI images.
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class SgiImageFile(ImageFile.ImageFile):
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format = "SGI"
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format_description = "SGI Image File Format"
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def _open(self) -> None:
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# HEAD
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assert self.fp is not None
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headlen = 512
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s = self.fp.read(headlen)
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if not _accept(s):
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msg = "Not an SGI image file"
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raise ValueError(msg)
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# compression : verbatim or RLE
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compression = s[2]
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# bpc : 1 or 2 bytes (8bits or 16bits)
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bpc = s[3]
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# dimension : 1, 2 or 3 (depending on xsize, ysize and zsize)
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dimension = i16(s, 4)
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# xsize : width
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xsize = i16(s, 6)
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# ysize : height
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ysize = i16(s, 8)
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# zsize : channels count
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zsize = i16(s, 10)
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# layout
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layout = bpc, dimension, zsize
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# determine mode from bits/zsize
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rawmode = ""
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try:
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rawmode = MODES[layout]
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except KeyError:
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pass
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if rawmode == "":
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msg = "Unsupported SGI image mode"
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raise ValueError(msg)
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self._size = xsize, ysize
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self._mode = rawmode.split(";")[0]
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if self.mode == "RGB":
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self.custom_mimetype = "image/rgb"
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# orientation -1 : scanlines begins at the bottom-left corner
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orientation = -1
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# decoder info
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if compression == 0:
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pagesize = xsize * ysize * bpc
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if bpc == 2:
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self.tile = [
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("SGI16", (0, 0) + self.size, headlen, (self.mode, 0, orientation))
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]
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else:
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self.tile = []
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offset = headlen
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for layer in self.mode:
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self.tile.append(
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("raw", (0, 0) + self.size, offset, (layer, 0, orientation))
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)
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offset += pagesize
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elif compression == 1:
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self.tile = [
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("sgi_rle", (0, 0) + self.size, headlen, (rawmode, orientation, bpc))
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]
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def _save(im: Image.Image, fp: IO[bytes], filename: str) -> None:
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if im.mode not in {"RGB", "RGBA", "L"}:
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msg = "Unsupported SGI image mode"
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raise ValueError(msg)
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# Get the keyword arguments
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info = im.encoderinfo
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# Byte-per-pixel precision, 1 = 8bits per pixel
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bpc = info.get("bpc", 1)
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if bpc not in (1, 2):
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msg = "Unsupported number of bytes per pixel"
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raise ValueError(msg)
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# Flip the image, since the origin of SGI file is the bottom-left corner
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orientation = -1
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# Define the file as SGI File Format
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magic_number = 474
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# Run-Length Encoding Compression - Unsupported at this time
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rle = 0
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# Number of dimensions (x,y,z)
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dim = 3
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# X Dimension = width / Y Dimension = height
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x, y = im.size
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if im.mode == "L" and y == 1:
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dim = 1
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elif im.mode == "L":
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dim = 2
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# Z Dimension: Number of channels
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z = len(im.mode)
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if dim in {1, 2}:
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z = 1
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# assert we've got the right number of bands.
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if len(im.getbands()) != z:
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msg = f"incorrect number of bands in SGI write: {z} vs {len(im.getbands())}"
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raise ValueError(msg)
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# Minimum Byte value
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pinmin = 0
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# Maximum Byte value (255 = 8bits per pixel)
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pinmax = 255
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# Image name (79 characters max, truncated below in write)
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filename = os.path.basename(filename)
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img_name = os.path.splitext(filename)[0].encode("ascii", "ignore")
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# Standard representation of pixel in the file
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colormap = 0
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fp.write(struct.pack(">h", magic_number))
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fp.write(o8(rle))
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fp.write(o8(bpc))
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fp.write(struct.pack(">H", dim))
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fp.write(struct.pack(">H", x))
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fp.write(struct.pack(">H", y))
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fp.write(struct.pack(">H", z))
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fp.write(struct.pack(">l", pinmin))
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fp.write(struct.pack(">l", pinmax))
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fp.write(struct.pack("4s", b"")) # dummy
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fp.write(struct.pack("79s", img_name)) # truncates to 79 chars
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fp.write(struct.pack("s", b"")) # force null byte after img_name
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fp.write(struct.pack(">l", colormap))
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fp.write(struct.pack("404s", b"")) # dummy
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rawmode = "L"
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if bpc == 2:
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rawmode = "L;16B"
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for channel in im.split():
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fp.write(channel.tobytes("raw", rawmode, 0, orientation))
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if hasattr(fp, "flush"):
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fp.flush()
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class SGI16Decoder(ImageFile.PyDecoder):
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_pulls_fd = True
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def decode(self, buffer: bytes) -> tuple[int, int]:
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assert self.fd is not None
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assert self.im is not None
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rawmode, stride, orientation = self.args
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pagesize = self.state.xsize * self.state.ysize
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zsize = len(self.mode)
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self.fd.seek(512)
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for band in range(zsize):
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channel = Image.new("L", (self.state.xsize, self.state.ysize))
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channel.frombytes(
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self.fd.read(2 * pagesize), "raw", "L;16B", stride, orientation
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)
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self.im.putband(channel.im, band)
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return -1, 0
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#
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# registry
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Image.register_decoder("SGI16", SGI16Decoder)
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Image.register_open(SgiImageFile.format, SgiImageFile, _accept)
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Image.register_save(SgiImageFile.format, _save)
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Image.register_mime(SgiImageFile.format, "image/sgi")
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Image.register_extensions(SgiImageFile.format, [".bw", ".rgb", ".rgba", ".sgi"])
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# End of file
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