--- /dev/null
+/* $Id: tif_thunder.c,v 1.1 2005-06-17 13:54:52 vp153 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) {
+ TIFFError(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: */
projects / opencv / blobdiff