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tif_thunder.c

/* $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: */

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