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