tif_thunder.c

Go to the documentation of this file.

/* $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: */