Aluode/PerceptionLabPortable
0
1#
2# The Python Imaging Library.
3# $Id$
4#
5# SGI image file handling
6#
7# See "The SGI Image File Format (Draft version 0.97)", Paul Haeberli.
8# <ftp://ftp.sgi.com/graphics/SGIIMAGESPEC>
9#
10#
11# History:
12# 2017-22-07 mb Add RLE decompression
13# 2016-16-10 mb Add save method without compression
14# 1995-09-10 fl Created
15#
16# Copyright (c) 2016 by Mickael Bonfill.
17# Copyright (c) 2008 by Karsten Hiddemann.
18# Copyright (c) 1997 by Secret Labs AB.
19# Copyright (c) 1995 by Fredrik Lundh.
20#
21# See the README file for information on usage and redistribution.
22#
23from __future__ import annotations
24
25import os
26import struct
27from typing import IO
28
29from . import Image, ImageFile
30from ._binary import i16be as i16
31from ._binary import o8
32
33
34def _accept(prefix: bytes) -> bool:
35 return len(prefix) >= 2 and i16(prefix) == 474
36
37
38MODES = {
39 (1, 1, 1): "L",
40 (1, 2, 1): "L",
41 (2, 1, 1): "L;16B",
42 (2, 2, 1): "L;16B",
43 (1, 3, 3): "RGB",
44 (2, 3, 3): "RGB;16B",
45 (1, 3, 4): "RGBA",
46 (2, 3, 4): "RGBA;16B",
47}
48
49
50##
51# Image plugin for SGI images.
52class SgiImageFile(ImageFile.ImageFile):
53 format = "SGI"
54 format_description = "SGI Image File Format"
55
56 def _open(self) -> None:
57 # HEAD
58 assert self.fp is not None
59
60 headlen = 512
61 s = self.fp.read(headlen)
62
63 if not _accept(s):
64 msg = "Not an SGI image file"
65 raise ValueError(msg)
66
67 # compression : verbatim or RLE
68 compression = s[2]
69
70 # bpc : 1 or 2 bytes (8bits or 16bits)
71 bpc = s[3]
72
73 # dimension : 1, 2 or 3 (depending on xsize, ysize and zsize)
74 dimension = i16(s, 4)
75
76 # xsize : width
77 xsize = i16(s, 6)
78
79 # ysize : height
80 ysize = i16(s, 8)
81
82 # zsize : channels count
83 zsize = i16(s, 10)
84
85 # determine mode from bits/zsize
86 try:
87 rawmode = MODES[(bpc, dimension, zsize)]
88 except KeyError:
89 msg = "Unsupported SGI image mode"
90 raise ValueError(msg)
91
92 self._size = xsize, ysize
93 self._mode = rawmode.split(";")[0]
94 if self.mode == "RGB":
95 self.custom_mimetype = "image/rgb"
96
97 # orientation -1 : scanlines begins at the bottom-left corner
98 orientation = -1
99
100 # decoder info
101 if compression == 0:
102 pagesize = xsize * ysize * bpc
103 if bpc == 2:
104 self.tile = [
105 ImageFile._Tile(
106 "SGI16",
107 (0, 0) + self.size,
108 headlen,
109 (self.mode, 0, orientation),
110 )
111 ]
112 else:
113 self.tile = []
114 offset = headlen
115 for layer in self.mode:
116 self.tile.append(
117 ImageFile._Tile(
118 "raw", (0, 0) + self.size, offset, (layer, 0, orientation)
119 )
120 )
121 offset += pagesize
122 elif compression == 1:
123 self.tile = [
124 ImageFile._Tile(
125 "sgi_rle", (0, 0) + self.size, headlen, (rawmode, orientation, bpc)
126 )
127 ]
128
129
130def _save(im: Image.Image, fp: IO[bytes], filename: str | bytes) -> None:
131 if im.mode not in {"RGB", "RGBA", "L"}:
132 msg = "Unsupported SGI image mode"
133 raise ValueError(msg)
134
135 # Get the keyword arguments
136 info = im.encoderinfo
137
138 # Byte-per-pixel precision, 1 = 8bits per pixel
139 bpc = info.get("bpc", 1)
140
141 if bpc not in (1, 2):
142 msg = "Unsupported number of bytes per pixel"
143 raise ValueError(msg)
144
145 # Flip the image, since the origin of SGI file is the bottom-left corner
146 orientation = -1
147 # Define the file as SGI File Format
148 magic_number = 474
149 # Run-Length Encoding Compression - Unsupported at this time
150 rle = 0
151
152 # X Dimension = width / Y Dimension = height
153 x, y = im.size
154 # Z Dimension: Number of channels
155 z = len(im.mode)
156 # Number of dimensions (x,y,z)
157 if im.mode == "L":
158 dimension = 1 if y == 1 else 2
159 else:
160 dimension = 3
161
162 # Minimum Byte value
163 pinmin = 0
164 # Maximum Byte value (255 = 8bits per pixel)
165 pinmax = 255
166 # Image name (79 characters max, truncated below in write)
167 img_name = os.path.splitext(os.path.basename(filename))[0]
168 if isinstance(img_name, str):
169 img_name = img_name.encode("ascii", "ignore")
170 # Standard representation of pixel in the file
171 colormap = 0
172 fp.write(struct.pack(">h", magic_number))
173 fp.write(o8(rle))
174 fp.write(o8(bpc))
175 fp.write(struct.pack(">H", dimension))
176 fp.write(struct.pack(">H", x))
177 fp.write(struct.pack(">H", y))
178 fp.write(struct.pack(">H", z))
179 fp.write(struct.pack(">l", pinmin))
180 fp.write(struct.pack(">l", pinmax))
181 fp.write(struct.pack("4s", b"")) # dummy
182 fp.write(struct.pack("79s", img_name)) # truncates to 79 chars
183 fp.write(struct.pack("s", b"")) # force null byte after img_name
184 fp.write(struct.pack(">l", colormap))
185 fp.write(struct.pack("404s", b"")) # dummy
186
187 rawmode = "L"
188 if bpc == 2:
189 rawmode = "L;16B"
190
191 for channel in im.split():
192 fp.write(channel.tobytes("raw", rawmode, 0, orientation))
193
194 if hasattr(fp, "flush"):
195 fp.flush()
196
197
198class SGI16Decoder(ImageFile.PyDecoder):
199 _pulls_fd = True
200
201 def decode(self, buffer: bytes | Image.SupportsArrayInterface) -> tuple[int, int]:
202 assert self.fd is not None
203 assert self.im is not None
204
205 rawmode, stride, orientation = self.args
206 pagesize = self.state.xsize * self.state.ysize
207 zsize = len(self.mode)
208 self.fd.seek(512)
209
210 for band in range(zsize):
211 channel = Image.new("L", (self.state.xsize, self.state.ysize))
212 channel.frombytes(
213 self.fd.read(2 * pagesize), "raw", "L;16B", stride, orientation
214 )
215 self.im.putband(channel.im, band)
216
217 return -1, 0
218
219
220#
221# registry
222
223
224Image.register_decoder("SGI16", SGI16Decoder)
225Image.register_open(SgiImageFile.format, SgiImageFile, _accept)
226Image.register_save(SgiImageFile.format, _save)
227Image.register_mime(SgiImageFile.format, "image/sgi")
228
229Image.register_extensions(SgiImageFile.format, [".bw", ".rgb", ".rgba", ".sgi"])
230
231# End of file
232