/* $Id: tif_thunder.c,v 1.5.2.1 2010-06-08 18:50:43 bfriesen 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: */

/*

 * Local Variables:

 * mode: c

 * c-basic-offset: 8

 * fill-column: 78

 * End:

 */