1
2 /*
3 * Copyright (c) 1988-1997 Sam Leffler
4 * Copyright (c) 1991-1997 Silicon Graphics, Inc.
5 *
6 * Permission to use, copy, modify, distribute, and sell this software and
7 * its documentation for any purpose is hereby granted without fee, provided
8 * that (i) the above copyright notices and this permission notice appear in
9 * all copies of the software and related documentation, and (ii) the names of
10 * Sam Leffler and Silicon Graphics may not be used in any advertising or
11 * publicity relating to the software without the specific, prior written
12 * permission of Sam Leffler and Silicon Graphics.
13 *
14 * THE SOFTWARE IS PROVIDED "AS-IS" AND WITHOUT WARRANTY OF ANY KIND,
15 * EXPRESS, IMPLIED OR OTHERWISE, INCLUDING WITHOUT LIMITATION, ANY
16 * WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
17 *
18 * IN NO EVENT SHALL SAM LEFFLER OR SILICON GRAPHICS BE LIABLE FOR
19 * ANY SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY KIND,
20 * OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
21 * WHETHER OR NOT ADVISED OF THE POSSIBILITY OF DAMAGE, AND ON ANY THEORY OF
22 * LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
23 * OF THIS SOFTWARE.
24 */
25
26 #include "tiffiop.h"
27 #include <assert.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 < maxpixels ) \
61 { \
62 if (npixels++ & 1) \
63 *op++ |= lastpixel; \
64 else \
65 op[0] = (uint8) (lastpixel << 4); \
66 } \
67 }
68
69 static int
ThunderSetupDecode(TIFF * tif)70 ThunderSetupDecode(TIFF* tif)
71 {
72 static const char module[] = "ThunderSetupDecode";
73
74 if( tif->tif_dir.td_bitspersample != 4 )
75 {
76 TIFFErrorExt(tif->tif_clientdata, module,
77 "Wrong bitspersample value (%d), Thunder decoder only supports 4bits per sample.",
78 (int) tif->tif_dir.td_bitspersample );
79 return 0;
80 }
81
82
83 return (1);
84 }
85
86 static int
ThunderDecode(TIFF * tif,uint8 * op,tmsize_t maxpixels)87 ThunderDecode(TIFF* tif, uint8* op, tmsize_t maxpixels)
88 {
89 static const char module[] = "ThunderDecode";
90 register unsigned char *bp;
91 register tmsize_t cc;
92 unsigned int lastpixel;
93 tmsize_t npixels;
94
95 bp = (unsigned char *)tif->tif_rawcp;
96 cc = tif->tif_rawcc;
97 lastpixel = 0;
98 npixels = 0;
99 while (cc > 0 && npixels < maxpixels) {
100 int n, delta;
101
102 n = *bp++, cc--;
103 switch (n & THUNDER_CODE) {
104 case THUNDER_RUN: /* pixel run */
105 /*
106 * Replicate the last pixel n times,
107 * where n is the lower-order 6 bits.
108 */
109 if (npixels & 1) {
110 op[0] |= lastpixel;
111 lastpixel = *op++; npixels++; n--;
112 } else
113 lastpixel |= lastpixel << 4;
114 npixels += n;
115 if (npixels < maxpixels) {
116 for (; n > 0; n -= 2)
117 *op++ = (uint8) lastpixel;
118 }
119 if (n == -1)
120 *--op &= 0xf0;
121 lastpixel &= 0xf;
122 break;
123 case THUNDER_2BITDELTAS: /* 2-bit deltas */
124 if ((delta = ((n >> 4) & 3)) != DELTA2_SKIP)
125 SETPIXEL(op, lastpixel + twobitdeltas[delta]);
126 if ((delta = ((n >> 2) & 3)) != DELTA2_SKIP)
127 SETPIXEL(op, lastpixel + twobitdeltas[delta]);
128 if ((delta = (n & 3)) != DELTA2_SKIP)
129 SETPIXEL(op, lastpixel + twobitdeltas[delta]);
130 break;
131 case THUNDER_3BITDELTAS: /* 3-bit deltas */
132 if ((delta = ((n >> 3) & 7)) != DELTA3_SKIP)
133 SETPIXEL(op, lastpixel + threebitdeltas[delta]);
134 if ((delta = (n & 7)) != DELTA3_SKIP)
135 SETPIXEL(op, lastpixel + threebitdeltas[delta]);
136 break;
137 case THUNDER_RAW: /* raw data */
138 SETPIXEL(op, n);
139 break;
140 }
141 }
142 tif->tif_rawcp = (uint8*) bp;
143 tif->tif_rawcc = cc;
144 if (npixels != maxpixels) {
145 #if defined(__WIN32__) && (defined(_MSC_VER) || defined(__MINGW32__))
146 TIFFErrorExt(tif->tif_clientdata, module,
147 "%s data at scanline %lu (%I64u != %I64u)",
148 npixels < maxpixels ? "Not enough" : "Too much",
149 (unsigned long) tif->tif_row,
150 (unsigned __int64) npixels,
151 (unsigned __int64) maxpixels);
152 #else
153 TIFFErrorExt(tif->tif_clientdata, module,
154 "%s data at scanline %lu (%llu != %llu)",
155 npixels < maxpixels ? "Not enough" : "Too much",
156 (unsigned long) tif->tif_row,
157 (unsigned long long) npixels,
158 (unsigned long long) maxpixels);
159 #endif
160 return (0);
161 }
162
163 return (1);
164 }
165
166 static int
ThunderDecodeRow(TIFF * tif,uint8 * buf,tmsize_t occ,uint16 s)167 ThunderDecodeRow(TIFF* tif, uint8* buf, tmsize_t occ, uint16 s)
168 {
169 static const char module[] = "ThunderDecodeRow";
170 uint8* row = buf;
171
172 (void) s;
173 if (occ % tif->tif_scanlinesize)
174 {
175 TIFFErrorExt(tif->tif_clientdata, module, "Fractional scanlines cannot be read");
176 return (0);
177 }
178 while (occ > 0) {
179 if (!ThunderDecode(tif, row, tif->tif_dir.td_imagewidth))
180 return (0);
181 occ -= tif->tif_scanlinesize;
182 row += tif->tif_scanlinesize;
183 }
184 return (1);
185 }
186
187 int
TIFFInitThunderScan(TIFF * tif,int scheme)188 TIFFInitThunderScan(TIFF* tif, int scheme)
189 {
190 (void) scheme;
191
192 tif->tif_setupdecode = ThunderSetupDecode;
193 tif->tif_decoderow = ThunderDecodeRow;
194 tif->tif_decodestrip = ThunderDecodeRow;
195 return (1);
196 }
197 #endif /* THUNDER_SUPPORT */
198
199 /* vim: set ts=8 sts=8 sw=8 noet: */
200 /*
201 * Local Variables:
202 * mode: c
203 * c-basic-offset: 8
204 * fill-column: 78
205 * End:
206 */
207