src/tiff/tif_thunder.c

   1 /* $Header$ */
   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
  55 static const int twobitdeltas[4] = { 0, 1, 0, -1 };
  56 static 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] = lastpixel << 4; \
  64 }
  65
  66 static int
  67 ThunderDecode(TIFF* tif, tidata_t op, tsize_t maxpixels)
  68 {
  69         register u_char *bp;
  70         register tsize_t cc;
  71         u_int lastpixel;
  72         tsize_t npixels;
  73
  74         bp = (u_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                         for (; n > 0; n -= 2)
  95                                 *op++ = lastpixel;
  96                         if (n == -1)
  97                                 *--op &= 0xf0;
  98                         lastpixel &= 0xf;
  99                         break;
 100                 case THUNDER_2BITDELTAS:        /* 2-bit deltas */
 101                         if ((delta = ((n >> 4) & 3)) != DELTA2_SKIP)
 102                                 SETPIXEL(op, lastpixel + twobitdeltas[delta]);
 103                         if ((delta = ((n >> 2) & 3)) != DELTA2_SKIP)
 104                                 SETPIXEL(op, lastpixel + twobitdeltas[delta]);
 105                         if ((delta = (n & 3)) != DELTA2_SKIP)
 106                                 SETPIXEL(op, lastpixel + twobitdeltas[delta]);
 107                         break;
 108                 case THUNDER_3BITDELTAS:        /* 3-bit deltas */
 109                         if ((delta = ((n >> 3) & 7)) != DELTA3_SKIP)
 110                                 SETPIXEL(op, lastpixel + threebitdeltas[delta]);
 111                         if ((delta = (n & 7)) != DELTA3_SKIP)
 112                                 SETPIXEL(op, lastpixel + threebitdeltas[delta]);
 113                         break;
 114                 case THUNDER_RAW:               /* raw data */
 115                         SETPIXEL(op, n);
 116                         break;
 117                 }
 118         }
 119         tif->tif_rawcp = (tidata_t) bp;
 120         tif->tif_rawcc = cc;
 121         if (npixels != maxpixels) {
 122                 TIFFError(tif->tif_name,
 123                     "ThunderDecode: %s data at scanline %ld (%lu != %lu)",
 124                     npixels < maxpixels ? "Not enough" : "Too much",
 125                     (long) tif->tif_row, (long) npixels, (long) maxpixels);
 126                 return (0);
 127         }
 128         return (1);
 129 }
 130
 131 static int LINKAGEMODE
 132 ThunderDecodeRow(TIFF* tif, tidata_t buf, tsize_t occ, tsample_t s)
 133 {
 134         tidata_t row = buf;
 135
 136         (void) s;
 137         while ((long)occ > 0) {
 138                 if (!ThunderDecode(tif, row, tif->tif_dir.td_imagewidth))
 139                         return (0);
 140                 occ -= tif->tif_scanlinesize;
 141                 row += tif->tif_scanlinesize;
 142         }
 143         return (1);
 144 }
 145
 146 int
 147 TIFFInitThunderScan(TIFF* tif, int scheme)
 148 {
 149         (void) scheme;
 150         tif->tif_decoderow = ThunderDecodeRow;
 151         tif->tif_decodestrip = ThunderDecodeRow;
 152         return (1);
 153 }
 154 #endif /* THUNDER_SUPPORT */