1/* $Id: tif_thunder.c,v 1.5.2.1 2010-06-08 18:50:43 bfriesen Exp $ */
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
55static const int twobitdeltas[4] = { 0, 1, 0, -1 };
56static 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
66static int
67ThunderDecode(TIFF* tif, tidata_t op, tsize_t maxpixels)
68{
69	register unsigned char *bp;
70	register tsize_t cc;
71	unsigned int lastpixel;
72	tsize_t npixels;
73
74	bp = (unsigned 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		TIFFErrorExt(tif->tif_clientdata, 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
133static int
134ThunderDecodeRow(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
148int
149TIFFInitThunderScan(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
158/* vim: set ts=8 sts=8 sw=8 noet: */
159/*
160 * Local Variables:
161 * mode: c
162 * c-basic-offset: 8
163 * fill-column: 78
164 * End:
165 */
166