text: /* $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 BLIK_OPENALPR_U_tiffiop_h //original-code:"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:
   */
  