PIL.SgiImagePlugin 源代码

#
# 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:
# 1995-09-10 fl   Created
#
# 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 PIL import Image, ImageFile, _binary

__version__ = "0.2"

i8 = _binary.i8
i16 = _binary.i16be


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


##
# Image plugin for SGI images.

[文档]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")
# # registry Image.register_open(SgiImageFile.format, SgiImageFile, _accept) 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