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] = (tidataval_t) (lastpixel << 4); \
64 }
65
66 static int
ThunderDecode(TIFF * tif,tidata_t op,tsize_t maxpixels)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 if (npixels < maxpixels) {
95 for (; n > 0; n -= 2)
96 *op++ = (tidataval_t) lastpixel;
97 }
98 if (n == -1)
99 *--op &= 0xf0;
100 lastpixel &= 0xf;
101 break;
102 case THUNDER_2BITDELTAS: /* 2-bit deltas */
103 if ((delta = ((n >> 4) & 3)) != DELTA2_SKIP)
104 SETPIXEL(op, lastpixel + twobitdeltas[delta]);
105 if ((delta = ((n >> 2) & 3)) != DELTA2_SKIP)
106 SETPIXEL(op, lastpixel + twobitdeltas[delta]);
107 if ((delta = (n & 3)) != DELTA2_SKIP)
108 SETPIXEL(op, lastpixel + twobitdeltas[delta]);
109 break;
110 case THUNDER_3BITDELTAS: /* 3-bit deltas */
111 if ((delta = ((n >> 3) & 7)) != DELTA3_SKIP)
112 SETPIXEL(op, lastpixel + threebitdeltas[delta]);
113 if ((delta = (n & 7)) != DELTA3_SKIP)
114 SETPIXEL(op, lastpixel + threebitdeltas[delta]);
115 break;
116 case THUNDER_RAW: /* raw data */
117 SETPIXEL(op, n);
118 break;
119 }
120 }
121 tif->tif_rawcp = (tidata_t) bp;
122 tif->tif_rawcc = cc;
123 if (npixels != maxpixels) {
124 TIFFError(tif->tif_name,
125 "ThunderDecode: %s data at scanline %ld (%lu != %lu)",
126 npixels < maxpixels ? "Not enough" : "Too much",
127 (long) tif->tif_row, (long) npixels, (long) maxpixels);
128 return (0);
129 }
130 return (1);
131 }
132
133 static int
ThunderDecodeRow(TIFF * tif,tidata_t buf,tsize_t occ,tsample_t s)134 ThunderDecodeRow(TIFF* tif, tidata_t buf, tsize_t occ, tsample_t s)
135 {
136 tidata_t row = buf;
137
138 (void) s;
139 while ((long)occ > 0) {
140 if (!ThunderDecode(tif, row, tif->tif_dir.td_imagewidth))
141 return (0);
142 occ -= tif->tif_scanlinesize;
143 row += tif->tif_scanlinesize;
144 }
145 return (1);
146 }
147
148 int
TIFFInitThunderScan(TIFF * tif,int scheme)149 TIFFInitThunderScan(TIFF* tif, int scheme)
150 {
151 (void) scheme;
152 tif->tif_decoderow = ThunderDecodeRow;
153 tif->tif_decodestrip = ThunderDecodeRow;
154 return (1);
155 }
156 #endif /* THUNDER_SUPPORT */
157