1 /* $Header: /usr/people/sam/tiff/libtiff/RCS/tif_thunder.c,v 1.24 1994/07/26 16:46:19 sam Exp $ */
2
3 /*
4 * Copyright (c) 1988, 1989, 1990, 1991, 1992, 1993, 1994 Sam Leffler
5 * Copyright (c) 1991, 1992, 1993, 1994 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 /*
28 * TIFF Library.
29 *
30 * ThunderScan 4-bit Compression Algorithm Support
31 */
32 #include "tiffiop.h"
33
34 /*
35 * ThunderScan uses an encoding scheme designed for
36 * 4-bit pixel values. Data is encoded in bytes, with
37 * each byte split into a 2-bit code word and a 6-bit
38 * data value. The encoding gives raw data, runs of
39 * pixels, or pixel values encoded as a delta from the
40 * previous pixel value. For the latter, either 2-bit
41 * or 3-bit delta values are used, with the deltas packed
42 * into a single byte.
43 */
44 #define THUNDER_DATA 0x3f /* mask for 6-bit data */
45 #define THUNDER_CODE 0xc0 /* mask for 2-bit code word */
46 /* code values */
47 #define THUNDER_RUN 0x00 /* run of pixels w/ encoded count */
48 #define THUNDER_2BITDELTAS 0x40 /* 3 pixels w/ encoded 2-bit deltas */
49 #define DELTA2_SKIP 2 /* skip code for 2-bit deltas */
50 #define THUNDER_3BITDELTAS 0x80 /* 2 pixels w/ encoded 3-bit deltas */
51 #define DELTA3_SKIP 4 /* skip code for 3-bit deltas */
52 #define THUNDER_RAW 0xc0 /* raw data encoded */
53
54 static const int twobitdeltas[4] = { 0, 1, 0, -1 };
55 static const int threebitdeltas[8] = { 0, 1, 2, 3, 0, -3, -2, -1 };
56
57 #define SETPIXEL(op, v) { \
58 lastpixel = (v) & 0xf; \
59 if (npixels++ & 1) \
60 *op++ |= lastpixel; \
61 else \
62 op[0] = lastpixel << 4; \
63 }
64
65 static int
ThunderDecode(TIFF * tif,tidata_t op,tsize_t maxpixels)66 ThunderDecode(TIFF* tif, tidata_t op, tsize_t maxpixels)
67 {
68 register u_char *bp;
69 register tsize_t cc;
70 u_int lastpixel;
71 tsize_t npixels;
72
73 bp = (u_char *)tif->tif_rawcp;
74 cc = tif->tif_rawcc;
75 lastpixel = 0;
76 npixels = 0;
77 while (cc > 0 && npixels < maxpixels) {
78 int n, delta;
79
80 n = *bp++, cc--;
81 switch (n & THUNDER_CODE) {
82 case THUNDER_RUN: /* pixel run */
83 /*
84 * Replicate the last pixel n times,
85 * where n is the lower-order 6 bits.
86 */
87 if (npixels & 1) {
88 op[0] |= lastpixel;
89 lastpixel = *op++; npixels++; n--;
90 } else
91 lastpixel |= lastpixel << 4;
92 npixels += n;
93 for (; n > 0; n -= 2)
94 *op++ = lastpixel;
95 if (n == -1)
96 *--op &= 0xf0;
97 lastpixel &= 0xf;
98 break;
99 case THUNDER_2BITDELTAS: /* 2-bit deltas */
100 if ((delta = ((n >> 4) & 3)) != DELTA2_SKIP)
101 SETPIXEL(op, lastpixel + twobitdeltas[delta]);
102 if ((delta = ((n >> 2) & 3)) != DELTA2_SKIP)
103 SETPIXEL(op, lastpixel + twobitdeltas[delta]);
104 if ((delta = (n & 3)) != DELTA2_SKIP)
105 SETPIXEL(op, lastpixel + twobitdeltas[delta]);
106 break;
107 case THUNDER_3BITDELTAS: /* 3-bit deltas */
108 if ((delta = ((n >> 3) & 7)) != DELTA3_SKIP)
109 SETPIXEL(op, lastpixel + threebitdeltas[delta]);
110 if ((delta = (n & 7)) != DELTA3_SKIP)
111 SETPIXEL(op, lastpixel + threebitdeltas[delta]);
112 break;
113 case THUNDER_RAW: /* raw data */
114 SETPIXEL(op, n);
115 break;
116 }
117 }
118 tif->tif_rawcp = (tidata_t) bp;
119 tif->tif_rawcc = cc;
120 if (npixels != maxpixels) {
121 TIFFError(tif->tif_name,
122 "ThunderDecode: %s data at scanline %ld (%lu != %lu)",
123 npixels < maxpixels ? "Not enough" : "Too much",
124 (long) tif->tif_row, (long) npixels, (long) maxpixels);
125 return (0);
126 }
127 return (1);
128 }
129
130 static int
ThunderDecodeRow(TIFF * tif,tidata_t buf,tsize_t occ,tsample_t s)131 ThunderDecodeRow(TIFF* tif, tidata_t buf, tsize_t occ, tsample_t s)
132 {
133 tidata_t row = buf;
134
135 while ((long)occ > 0) {
136 if (!ThunderDecode(tif, row, tif->tif_dir.td_imagewidth))
137 return (0);
138 occ -= tif->tif_scanlinesize;
139 row += tif->tif_scanlinesize;
140 }
141 return (1);
142 }
143
144 int
TIFFInitThunderScan(TIFF * tif)145 TIFFInitThunderScan(TIFF* tif)
146 {
147 tif->tif_decoderow = ThunderDecodeRow;
148 tif->tif_decodestrip = ThunderDecodeRow;
149 return (1);
150 }
151