#
# 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.
#
from . import Image, ImageFile
from ._binary import i8, o8, i16be as i16
from ._util import py3
import struct
import os
__version__ = "0.3"
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.
[文档]class SgiImageFile(ImageFile.ImageFile):
format = "SGI"
format_description = "SGI Image File Format"
def _open(self):
# HEAD
headlen = 512
s = self.fp.read(headlen)
# magic number : 474
if i16(s) != 474:
raise ValueError("Not an SGI image file")
# compression : verbatim or RLE
compression = i8(s[2])
# bpc : 1 or 2 bytes (8bits or 16bits)
bpc = i8(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 == "":
raise ValueError("Unsupported SGI image mode")
self._size = xsize, ysize
self.mode = rawmode.split(";")[0]
# 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":
raise ValueError("Unsupported SGI image mode")
# 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):
raise ValueError("Unsupported number of bytes per pixel")
# Flip the image, since the origin of SGI file is the bottom-left corner
orientation = -1
# Define the file as SGI File Format
magicNumber = 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:
raise ValueError("incorrect number of bands in SGI write: %s vs %s" %
(z, len(im.getbands())))
# Minimum Byte value
pinmin = 0
# Maximum Byte value (255 = 8bits per pixel)
pinmax = 255
# Image name (79 characters max, truncated below in write)
imgName = os.path.splitext(os.path.basename(filename))[0]
if py3:
imgName = imgName.encode('ascii', 'ignore')
# Standard representation of pixel in the file
colormap = 0
fp.write(struct.pack('>h', magicNumber))
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', imgName)) # truncates to 79 chars
fp.write(struct.pack('s', b'')) # force null byte after imgname
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))
fp.close()
[文档]class SGI16Decoder(ImageFile.PyDecoder):
_pulls_fd = True
[文档] 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_mime(SgiImageFile.format, "image/rgb")
Image.register_extensions(SgiImageFile.format,
[".bw", ".rgb", ".rgba", ".sgi"])
# End of file