| /* $Id: tif_thunder.c,v 1.27 2009/09/06 13:11:29 drolon 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: */ |