#
# 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:
# 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
import struct
import os
__version__ = "0.3"
def _accept(prefix):
return len(prefix) >= 2 and i16(prefix) == 474
##
# Image plugin for SGI images.
[docs]class SgiImageFile(ImageFile.ImageFile):
format = "SGI"
format_description = "SGI Image File Format"
def _open(self):
# HEAD
s = self.fp.read(512)
if i16(s) != 474:
raise ValueError("Not an SGI image file")
# relevant header entries
compression = i8(s[2])
# bytes, dimension, zsize
layout = i8(s[3]), i16(s[4:]), i16(s[10:])
# determine mode from bytes/zsize
if layout == (1, 2, 1) or layout == (1, 1, 1):
self.mode = "L"
elif layout == (1, 3, 3):
self.mode = "RGB"
elif layout == (1, 3, 4):
self.mode = "RGBA"
else:
raise ValueError("Unsupported SGI image mode")
# size
self.size = i16(s[6:]), i16(s[8:])
# decoder info
if compression == 0:
offset = 512
pagesize = self.size[0]*self.size[1]*layout[0]
self.tile = []
for layer in self.mode:
self.tile.append(
("raw", (0, 0)+self.size, offset, (layer, 0, -1)))
offset = offset + pagesize
elif compression == 1:
raise ValueError("SGI RLE encoding not supported")
def _save(im, fp, filename):
if im.mode != "RGB" and im.mode != "RGBA" and im.mode != "L":
raise ValueError("Unsupported SGI image mode")
# Flip the image, since the origin of SGI file is the bottom-left corner
im = im.transpose(Image.FLIP_TOP_BOTTOM)
# Define the file as SGI File Format
magicNumber = 474
# Run-Length Encoding Compression - Unsupported at this time
rle = 0
# Byte-per-pixel precision, 1 = 8bits per pixel
bpc = 1
# 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
# 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 str is not bytes:
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
#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())))
for channel in im.split():
fp.write(channel.tobytes())
fp.close()
#
# registry
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_extension(SgiImageFile.format, ".bw")
Image.register_extension(SgiImageFile.format, ".rgb")
Image.register_extension(SgiImageFile.format, ".rgba")
Image.register_extension(SgiImageFile.format, ".sgi")
# End of file