This is tif_thunder.c in view mode; [Download] [Up]
#ifndef lint
static char rcsid[] = "$Header: /usr/people/sam/tiff/libtiff/RCS/tif_thunder.c,v 1.21 92/10/21 13:42:20 sam Exp $";
#endif
/*
* Copyright (c) 1988, 1989, 1990, 1991, 1992 Sam Leffler
* Copyright (c) 1991, 1992 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.
*/
/*
* TIFF Library.
*
* ThunderScan 4-bit Compression Algorithm Support
*/
#include "tiffiop.h"
/*
* 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] = lastpixel << 4; \
}
static int
DECLARE3(ThunderDecode, TIFF*, tif, register u_char*, op, u_long, maxpixels)
{
register u_char *bp;
register int n, cc, delta;
register u_int lastpixel;
register u_long npixels;
bp = (u_char *)tif->tif_rawcp;
cc = tif->tif_rawcc;
lastpixel = npixels = 0;
while (cc > 0 && npixels < maxpixels) {
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;
for (; n > 0; n -= 2)
*op++ = 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 = (char *)bp;
tif->tif_rawcc = cc;
if (npixels != maxpixels) {
TIFFError(tif->tif_name,
"ThunderDecode: %s data at scanline %ld (%lu != %lu)",
npixels < maxpixels ? "Not enough" : "Too much",
tif->tif_row, npixels, maxpixels);
return (0);
}
return (1);
}
static int
DECLARE4(ThunderDecodeRow, TIFF*, tif, u_char*, buf, u_long, occ, u_int, s)
{
u_char *row = buf;
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
DECLARE1(TIFFInitThunderScan, TIFF*, tif)
{
tif->tif_decoderow = ThunderDecodeRow;
tif->tif_decodestrip = ThunderDecodeRow;
return (1);
}
These are the contents of the former NiCE NeXT User Group NeXTSTEP/OpenStep software archive, currently hosted by Netfuture.ch.