/* $Id: tif_thunder.c,v 1.5 2005/12/21 12:23:13 joris Exp $ */ | |
/* | |
* Copyright (c) 1988-1997 Sam Leffler | |
* Copyright (c) 1991-1997 Silicon Graphics, Inc. | |
* | |
* Permission to use, copy, modify, distribute, and sell this software and | |
* its documentation for any purpose is hereby granted without fee, provided | |
* that (i) the above copyright notices and this permission notice appear in | |
* all copies of the software and related documentation, and (ii) the names of | |
* Sam Leffler and Silicon Graphics may not be used in any advertising or | |
* publicity relating to the software without the specific, prior written | |
* permission of Sam Leffler and Silicon Graphics. | |
* | |
* THE SOFTWARE IS PROVIDED "AS-IS" AND WITHOUT WARRANTY OF ANY KIND, | |
* EXPRESS, IMPLIED OR OTHERWISE, INCLUDING WITHOUT LIMITATION, ANY | |
* WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. | |
* | |
* IN NO EVENT SHALL SAM LEFFLER OR SILICON GRAPHICS BE LIABLE FOR | |
* ANY SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY KIND, | |
* OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, | |
* WHETHER OR NOT ADVISED OF THE POSSIBILITY OF DAMAGE, AND ON ANY THEORY OF | |
* LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE | |
* OF THIS SOFTWARE. | |
*/ | |
#include "tiffiop.h" | |
#ifdef THUNDER_SUPPORT | |
/* | |
* TIFF Library. | |
* | |
* ThunderScan 4-bit Compression Algorithm Support | |
*/ | |
/* | |
* ThunderScan uses an encoding scheme designed for | |
* 4-bit pixel values. Data is encoded in bytes, with | |
* each byte split into a 2-bit code word and a 6-bit | |
* data value. The encoding gives raw data, runs of | |
* pixels, or pixel values encoded as a delta from the | |
* previous pixel value. For the latter, either 2-bit | |
* or 3-bit delta values are used, with the deltas packed | |
* into a single byte. | |
*/ | |
#define THUNDER_DATA 0x3f /* mask for 6-bit data */ | |
#define THUNDER_CODE 0xc0 /* mask for 2-bit code word */ | |
/* code values */ | |
#define THUNDER_RUN 0x00 /* run of pixels w/ encoded count */ | |
#define THUNDER_2BITDELTAS 0x40 /* 3 pixels w/ encoded 2-bit deltas */ | |
#define DELTA2_SKIP 2 /* skip code for 2-bit deltas */ | |
#define THUNDER_3BITDELTAS 0x80 /* 2 pixels w/ encoded 3-bit deltas */ | |
#define DELTA3_SKIP 4 /* skip code for 3-bit deltas */ | |
#define THUNDER_RAW 0xc0 /* raw data encoded */ | |
static const int twobitdeltas[4] = { 0, 1, 0, -1 }; | |
static const int threebitdeltas[8] = { 0, 1, 2, 3, 0, -3, -2, -1 }; | |
#define SETPIXEL(op, v) { \ | |
lastpixel = (v) & 0xf; \ | |
if (npixels++ & 1) \ | |
*op++ |= lastpixel; \ | |
else \ | |
op[0] = (tidataval_t) (lastpixel << 4); \ | |
} | |
static int | |
ThunderDecode(TIFF* tif, tidata_t op, tsize_t maxpixels) | |
{ | |
register unsigned char *bp; | |
register tsize_t cc; | |
unsigned int lastpixel; | |
tsize_t npixels; | |
bp = (unsigned char *)tif->tif_rawcp; | |
cc = tif->tif_rawcc; | |
lastpixel = 0; | |
npixels = 0; | |
while (cc > 0 && npixels < maxpixels) { | |
int n, delta; | |
n = *bp++, cc--; | |
switch (n & THUNDER_CODE) { | |
case THUNDER_RUN: /* pixel run */ | |
/* | |
* Replicate the last pixel n times, | |
* where n is the lower-order 6 bits. | |
*/ | |
if (npixels & 1) { | |
op[0] |= lastpixel; | |
lastpixel = *op++; npixels++; n--; | |
} else | |
lastpixel |= lastpixel << 4; | |
npixels += n; | |
if (npixels < maxpixels) { | |
for (; n > 0; n -= 2) | |
*op++ = (tidataval_t) lastpixel; | |
} | |
if (n == -1) | |
*--op &= 0xf0; | |
lastpixel &= 0xf; | |
break; | |
case THUNDER_2BITDELTAS: /* 2-bit deltas */ | |
if ((delta = ((n >> 4) & 3)) != DELTA2_SKIP) | |
SETPIXEL(op, lastpixel + twobitdeltas[delta]); | |
if ((delta = ((n >> 2) & 3)) != DELTA2_SKIP) | |
SETPIXEL(op, lastpixel + twobitdeltas[delta]); | |
if ((delta = (n & 3)) != DELTA2_SKIP) | |
SETPIXEL(op, lastpixel + twobitdeltas[delta]); | |
break; | |
case THUNDER_3BITDELTAS: /* 3-bit deltas */ | |
if ((delta = ((n >> 3) & 7)) != DELTA3_SKIP) | |
SETPIXEL(op, lastpixel + threebitdeltas[delta]); | |
if ((delta = (n & 7)) != DELTA3_SKIP) | |
SETPIXEL(op, lastpixel + threebitdeltas[delta]); | |
break; | |
case THUNDER_RAW: /* raw data */ | |
SETPIXEL(op, n); | |
break; | |
} | |
} | |
tif->tif_rawcp = (tidata_t) bp; | |
tif->tif_rawcc = cc; | |
if (npixels != maxpixels) { | |
TIFFErrorExt(tif->tif_clientdata, tif->tif_name, | |
"ThunderDecode: %s data at scanline %ld (%lu != %lu)", | |
npixels < maxpixels ? "Not enough" : "Too much", | |
(long) tif->tif_row, (long) npixels, (long) maxpixels); | |
return (0); | |
} | |
return (1); | |
} | |
static int | |
ThunderDecodeRow(TIFF* tif, tidata_t buf, tsize_t occ, tsample_t s) | |
{ | |
tidata_t row = buf; | |
(void) s; | |
while ((long)occ > 0) { | |
if (!ThunderDecode(tif, row, tif->tif_dir.td_imagewidth)) | |
return (0); | |
occ -= tif->tif_scanlinesize; | |
row += tif->tif_scanlinesize; | |
} | |
return (1); | |
} | |
int | |
TIFFInitThunderScan(TIFF* tif, int scheme) | |
{ | |
(void) scheme; | |
tif->tif_decoderow = ThunderDecodeRow; | |
tif->tif_decodestrip = ThunderDecodeRow; | |
return (1); | |
} | |
#endif /* THUNDER_SUPPORT */ | |
/* vim: set ts=8 sts=8 sw=8 noet: */ |