Source code for PIL.SgiImagePlugin

#
# The Python Imaging Library.
# $Id$
#
# SGI image file handling
#
# See "The SGI Image File Format (Draft version 0.97)", Paul Haeberli.
# <ftp://ftp.sgi.com/graphics/SGIIMAGESPEC>
#
#
# History:
# 2017-22-07 mb   Add RLE decompression
# 2016-16-10 mb   Add save method without compression
# 1995-09-10 fl   Created
#
# Copyright (c) 2016 by Mickael Bonfill.
# Copyright (c) 2008 by Karsten Hiddemann.
# Copyright (c) 1997 by Secret Labs AB.
# Copyright (c) 1995 by Fredrik Lundh.
#
# See the README file for information on usage and redistribution.
#


import os
import struct

from . import Image, ImageFile
from ._binary import i16be as i16
from ._binary import o8


def _accept(prefix):
    return len(prefix) >= 2 and i16(prefix) == 474


MODES = {
    (1, 1, 1): "L",
    (1, 2, 1): "L",
    (2, 1, 1): "L;16B",
    (2, 2, 1): "L;16B",
    (1, 3, 3): "RGB",
    (2, 3, 3): "RGB;16B",
    (1, 3, 4): "RGBA",
    (2, 3, 4): "RGBA;16B",
}


##
# Image plugin for SGI images.
[docs]class SgiImageFile(ImageFile.ImageFile): format = "SGI" format_description = "SGI Image File Format" def _open(self): # HEAD headlen = 512 s = self.fp.read(headlen) if not _accept(s): msg = "Not an SGI image file" raise ValueError(msg) # compression : verbatim or RLE compression = s[2] # bpc : 1 or 2 bytes (8bits or 16bits) bpc = s[3] # dimension : 1, 2 or 3 (depending on xsize, ysize and zsize) dimension = i16(s, 4) # xsize : width xsize = i16(s, 6) # ysize : height ysize = i16(s, 8) # zsize : channels count zsize = i16(s, 10) # layout layout = bpc, dimension, zsize # determine mode from bits/zsize rawmode = "" try: rawmode = MODES[layout] except KeyError: pass if rawmode == "": msg = "Unsupported SGI image mode" raise ValueError(msg) self._size = xsize, ysize self.mode = rawmode.split(";")[0] if self.mode == "RGB": self.custom_mimetype = "image/rgb" # orientation -1 : scanlines begins at the bottom-left corner orientation = -1 # decoder info if compression == 0: pagesize = xsize * ysize * bpc if bpc == 2: self.tile = [ ("SGI16", (0, 0) + self.size, headlen, (self.mode, 0, orientation)) ] else: self.tile = [] offset = headlen for layer in self.mode: self.tile.append( ("raw", (0, 0) + self.size, offset, (layer, 0, orientation)) ) offset += pagesize elif compression == 1: self.tile = [ ("sgi_rle", (0, 0) + self.size, headlen, (rawmode, orientation, bpc)) ]
def _save(im, fp, filename): if im.mode != "RGB" and im.mode != "RGBA" and im.mode != "L": msg = "Unsupported SGI image mode" raise ValueError(msg) # Get the keyword arguments info = im.encoderinfo # Byte-per-pixel precision, 1 = 8bits per pixel bpc = info.get("bpc", 1) if bpc not in (1, 2): msg = "Unsupported number of bytes per pixel" raise ValueError(msg) # Flip the image, since the origin of SGI file is the bottom-left corner orientation = -1 # Define the file as SGI File Format magic_number = 474 # Run-Length Encoding Compression - Unsupported at this time rle = 0 # Number of dimensions (x,y,z) dim = 3 # X Dimension = width / Y Dimension = height x, y = im.size if im.mode == "L" and y == 1: dim = 1 elif im.mode == "L": dim = 2 # Z Dimension: Number of channels z = len(im.mode) if dim == 1 or dim == 2: z = 1 # assert we've got the right number of bands. if len(im.getbands()) != z: msg = f"incorrect number of bands in SGI write: {z} vs {len(im.getbands())}" raise ValueError(msg) # Minimum Byte value pinmin = 0 # Maximum Byte value (255 = 8bits per pixel) pinmax = 255 # Image name (79 characters max, truncated below in write) img_name = os.path.splitext(os.path.basename(filename))[0] img_name = img_name.encode("ascii", "ignore") # Standard representation of pixel in the file colormap = 0 fp.write(struct.pack(">h", magic_number)) fp.write(o8(rle)) fp.write(o8(bpc)) fp.write(struct.pack(">H", dim)) fp.write(struct.pack(">H", x)) fp.write(struct.pack(">H", y)) fp.write(struct.pack(">H", z)) fp.write(struct.pack(">l", pinmin)) fp.write(struct.pack(">l", pinmax)) fp.write(struct.pack("4s", b"")) # dummy fp.write(struct.pack("79s", img_name)) # truncates to 79 chars fp.write(struct.pack("s", b"")) # force null byte after img_name fp.write(struct.pack(">l", colormap)) fp.write(struct.pack("404s", b"")) # dummy rawmode = "L" if bpc == 2: rawmode = "L;16B" for channel in im.split(): fp.write(channel.tobytes("raw", rawmode, 0, orientation)) if hasattr(fp, "flush"): fp.flush()
[docs]class SGI16Decoder(ImageFile.PyDecoder): _pulls_fd = True
[docs] def decode(self, buffer): rawmode, stride, orientation = self.args pagesize = self.state.xsize * self.state.ysize zsize = len(self.mode) self.fd.seek(512) for band in range(zsize): channel = Image.new("L", (self.state.xsize, self.state.ysize)) channel.frombytes( self.fd.read(2 * pagesize), "raw", "L;16B", stride, orientation ) self.im.putband(channel.im, band) return -1, 0
# # registry Image.register_decoder("SGI16", SGI16Decoder) Image.register_open(SgiImageFile.format, SgiImageFile, _accept) Image.register_save(SgiImageFile.format, _save) Image.register_mime(SgiImageFile.format, "image/sgi") Image.register_extensions(SgiImageFile.format, [".bw", ".rgb", ".rgba", ".sgi"]) # End of file