1 /* PDFlib GmbH cvsid:
2 * $Id: tif_thunder.c,v 1.10 2005/12/21 13:22:05 rjs Exp $ */
3
4 /*
5 * Copyright (c) 1988-1997 Sam Leffler
6 * Copyright (c) 1991-1997 Silicon Graphics, Inc.
7 *
8 * Permission to use, copy, modify, distribute, and sell this software and
9 * its documentation for any purpose is hereby granted without fee, provided
10 * that (i) the above copyright notices and this permission notice appear in
11 * all copies of the software and related documentation, and (ii) the names of
12 * Sam Leffler and Silicon Graphics may not be used in any advertising or
13 * publicity relating to the software without the specific, prior written
14 * permission of Sam Leffler and Silicon Graphics.
15 *
16 * THE SOFTWARE IS PROVIDED "AS-IS" AND WITHOUT WARRANTY OF ANY KIND,
17 * EXPRESS, IMPLIED OR OTHERWISE, INCLUDING WITHOUT LIMITATION, ANY
18 * WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
19 *
20 * IN NO EVENT SHALL SAM LEFFLER OR SILICON GRAPHICS BE LIABLE FOR
21 * ANY SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY KIND,
22 * OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
23 * WHETHER OR NOT ADVISED OF THE POSSIBILITY OF DAMAGE, AND ON ANY THEORY OF
24 * LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
25 * OF THIS SOFTWARE.
26 */
27
28 #include "tiffiop.h"
29 #ifdef THUNDER_SUPPORT
30 /*
31 * TIFF Library.
32 *
33 * ThunderScan 4-bit Compression Algorithm Support
34 */
35
36 /*
37 * ThunderScan uses an encoding scheme designed for
38 * 4-bit pixel values. Data is encoded in bytes, with
39 * each byte split into a 2-bit code word and a 6-bit
40 * data value. The encoding gives raw data, runs of
41 * pixels, or pixel values encoded as a delta from the
42 * previous pixel value. For the latter, either 2-bit
43 * or 3-bit delta values are used, with the deltas packed
44 * into a single byte.
45 */
46 #define THUNDER_DATA 0x3f /* mask for 6-bit data */
47 #define THUNDER_CODE 0xc0 /* mask for 2-bit code word */
48 /* code values */
49 #define THUNDER_RUN 0x00 /* run of pixels w/ encoded count */
50 #define THUNDER_2BITDELTAS 0x40 /* 3 pixels w/ encoded 2-bit deltas */
51 #define DELTA2_SKIP 2 /* skip code for 2-bit deltas */
52 #define THUNDER_3BITDELTAS 0x80 /* 2 pixels w/ encoded 3-bit deltas */
53 #define DELTA3_SKIP 4 /* skip code for 3-bit deltas */
54 #define THUNDER_RAW 0xc0 /* raw data encoded */
55
56 static const int twobitdeltas[4] = { 0, 1, 0, -1 };
57 static const int threebitdeltas[8] = { 0, 1, 2, 3, 0, -3, -2, -1 };
58
59 #define SETPIXEL(op, v) { \
60 lastpixel = (v) & 0xf; \
61 if (npixels++ & 1) \
62 *op++ |= lastpixel; \
63 else \
64 op[0] = (tidataval_t) (lastpixel << 4); \
65 }
66
67 static int
ThunderDecode(TIFF * tif,tidata_t op,tsize_t maxpixels)68 ThunderDecode(TIFF* tif, tidata_t op, tsize_t maxpixels)
69 {
70 register unsigned char *bp;
71 register tsize_t cc;
72 unsigned int lastpixel;
73 tsize_t npixels;
74
75 bp = (unsigned char *)tif->tif_rawcp;
76 cc = tif->tif_rawcc;
77 lastpixel = 0;
78 npixels = 0;
79 while (cc > 0 && npixels < maxpixels) {
80 int n, delta;
81
82 n = *bp++, cc--;
83 switch (n & THUNDER_CODE) {
84 case THUNDER_RUN: /* pixel run */
85 /*
86 * Replicate the last pixel n times,
87 * where n is the lower-order 6 bits.
88 */
89 if (npixels & 1) {
90 op[0] |= lastpixel;
91 lastpixel = *op++; npixels++; n--;
92 } else
93 lastpixel |= lastpixel << 4;
94 npixels += n;
95 if (npixels < maxpixels) {
96 for (; n > 0; n -= 2)
97 *op++ = (tidataval_t) lastpixel;
98 }
99 if (n == -1)
100 *--op &= 0xf0;
101 lastpixel &= 0xf;
102 break;
103 case THUNDER_2BITDELTAS: /* 2-bit deltas */
104 if ((delta = ((n >> 4) & 3)) != DELTA2_SKIP)
105 SETPIXEL(op, lastpixel + twobitdeltas[delta]);
106 if ((delta = ((n >> 2) & 3)) != DELTA2_SKIP)
107 SETPIXEL(op, lastpixel + twobitdeltas[delta]);
108 if ((delta = (n & 3)) != DELTA2_SKIP)
109 SETPIXEL(op, lastpixel + twobitdeltas[delta]);
110 break;
111 case THUNDER_3BITDELTAS: /* 3-bit deltas */
112 if ((delta = ((n >> 3) & 7)) != DELTA3_SKIP)
113 SETPIXEL(op, lastpixel + threebitdeltas[delta]);
114 if ((delta = (n & 7)) != DELTA3_SKIP)
115 SETPIXEL(op, lastpixel + threebitdeltas[delta]);
116 break;
117 case THUNDER_RAW: /* raw data */
118 SETPIXEL(op, n);
119 break;
120 }
121 }
122 tif->tif_rawcp = (tidata_t) bp;
123 tif->tif_rawcc = cc;
124 if (npixels != maxpixels) {
125 _TIFFError(tif, tif->tif_name,
126 "ThunderDecode: %s data at scanline %ld (%lu != %lu)",
127 npixels < maxpixels ? "Not enough" : "Too much",
128 (long) tif->tif_row, (long) npixels, (long) maxpixels);
129 return (0);
130 }
131 return (1);
132 }
133
134 static int
ThunderDecodeRow(TIFF * tif,tidata_t buf,tsize_t occ,tsample_t s)135 ThunderDecodeRow(TIFF* tif, tidata_t buf, tsize_t occ, tsample_t s)
136 {
137 tidata_t row = buf;
138
139 (void) s;
140 while ((long)occ > 0) {
141 if (!ThunderDecode(tif, row, tif->tif_dir.td_imagewidth))
142 return (0);
143 occ -= tif->tif_scanlinesize;
144 row += tif->tif_scanlinesize;
145 }
146 return (1);
147 }
148
149 int
TIFFInitThunderScan(TIFF * tif,int scheme)150 TIFFInitThunderScan(TIFF* tif, int scheme)
151 {
152 (void) scheme;
153 tif->tif_decoderow = ThunderDecodeRow;
154 tif->tif_decodestrip = ThunderDecodeRow;
155 return (1);
156 }
157 #endif /* THUNDER_SUPPORT */
158
159 /* vim: set ts=8 sts=8 sw=8 noet: */
160