| 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] = (tidataval_t) (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 | if (npixels < maxpixels) { |
| 95 | for (; n > 0; n -= 2) |
| 96 | *op++ = (tidataval_t) lastpixel; |
| 97 | } |
| 98 | if (n == -1) |
| 99 | *--op &= 0xf0; |
| 100 | lastpixel &= 0xf; |
| 101 | break; |
| 102 | case THUNDER_2BITDELTAS: /* 2-bit deltas */ |
| 103 | if ((delta = ((n >> 4) & 3)) != DELTA2_SKIP) |
| 104 | SETPIXEL(op, lastpixel + twobitdeltas[delta]); |
| 105 | if ((delta = ((n >> 2) & 3)) != DELTA2_SKIP) |
| 106 | SETPIXEL(op, lastpixel + twobitdeltas[delta]); |
| 107 | if ((delta = (n & 3)) != DELTA2_SKIP) |
| 108 | SETPIXEL(op, lastpixel + twobitdeltas[delta]); |
| 109 | break; |
| 110 | case THUNDER_3BITDELTAS: /* 3-bit deltas */ |
| 111 | if ((delta = ((n >> 3) & 7)) != DELTA3_SKIP) |
| 112 | SETPIXEL(op, lastpixel + threebitdeltas[delta]); |
| 113 | if ((delta = (n & 7)) != DELTA3_SKIP) |
| 114 | SETPIXEL(op, lastpixel + threebitdeltas[delta]); |
| 115 | break; |
| 116 | case THUNDER_RAW: /* raw data */ |
| 117 | SETPIXEL(op, n); |
| 118 | break; |
| 119 | } |
| 120 | } |
| 121 | tif->tif_rawcp = (tidata_t) bp; |
| 122 | tif->tif_rawcc = cc; |
| 123 | if (npixels != maxpixels) { |
| 124 | TIFFError(tif->tif_name, |
| 125 | "ThunderDecode: %s data at scanline %ld (%lu != %lu)", |
| 126 | npixels < maxpixels ? "Not enough" : "Too much", |
| 127 | (long) tif->tif_row, (long) npixels, (long) maxpixels); |
| 128 | return (0); |
| 129 | } |
| 130 | return (1); |
| 131 | } |
| 132 | |
| 133 | static int |
| 134 | ThunderDecodeRow(TIFF* tif, tidata_t buf, tsize_t occ, tsample_t s) |
| 135 | { |
| 136 | tidata_t row = buf; |
| 137 | |
| 138 | (void) s; |
| 139 | while ((long)occ > 0) { |
| 140 | if (!ThunderDecode(tif, row, tif->tif_dir.td_imagewidth)) |
| 141 | return (0); |
| 142 | occ -= tif->tif_scanlinesize; |
| 143 | row += tif->tif_scanlinesize; |
| 144 | } |
| 145 | return (1); |
| 146 | } |
| 147 | |
| 148 | int |
| 149 | TIFFInitThunderScan(TIFF* tif, int scheme) |
| 150 | { |
| 151 | (void) scheme; |
| 152 | tif->tif_decoderow = ThunderDecodeRow; |
| 153 | tif->tif_decodestrip = ThunderDecodeRow; |
| 154 | return (1); |
| 155 | } |
| 156 | #endif /* THUNDER_SUPPORT */ |