/*

* 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"

#include <assert.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 < maxpixels ) \

{ \

if (npixels++ & 1) \

*op++ |= lastpixel; \

else \

op[0] = (uint8) (lastpixel << 4); \

} \

}

static int

ThunderSetupDecode(TIFF* tif)

{

static const char module[] = "ThunderSetupDecode";

if( tif->tif_dir.td_bitspersample != 4 )

{

TIFFErrorExt(tif->tif_clientdata, module,

"Wrong bitspersample value (%d), Thunder decoder only supports 4bits per sample.",

(int) tif->tif_dir.td_bitspersample );

return 0;

}

return (1);

}

static int

ThunderDecode(TIFF* tif, uint8* op, tmsize_t maxpixels)

{

static const char module[] = "ThunderDecode";

register unsigned char *bp;

register tmsize_t cc;

unsigned int lastpixel;

tmsize_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++ = (uint8) lastpixel;

}

if (n == -1)

*--op &= 0xf0;

lastpixel &= 0xf;

break;

case THUNDER_2BITDELTAS: /* 2-bit deltas */

if ((delta = ((n >> 4) & 3)) != DELTA2_SKIP)

SETPIXEL(op, (unsigned)((int)lastpixel + twobitdeltas[delta]));

if ((delta = ((n >> 2) & 3)) != DELTA2_SKIP)

SETPIXEL(op, (unsigned)((int)lastpixel + twobitdeltas[delta]));

if ((delta = (n & 3)) != DELTA2_SKIP)

SETPIXEL(op, (unsigned)((int)lastpixel + twobitdeltas[delta]));

break;

case THUNDER_3BITDELTAS: /* 3-bit deltas */

if ((delta = ((n >> 3) & 7)) != DELTA3_SKIP)

SETPIXEL(op, (unsigned)((int)lastpixel + threebitdeltas[delta]));

if ((delta = (n & 7)) != DELTA3_SKIP)

SETPIXEL(op, (unsigned)((int)lastpixel + threebitdeltas[delta]));

break;

case THUNDER_RAW: /* raw data */

SETPIXEL(op, n);

break;

}

}

tif->tif_rawcp = (uint8*) bp;

tif->tif_rawcc = cc;

if (npixels != maxpixels) {

#if defined(__WIN32__) && (defined(_MSC_VER) || defined(__MINGW32__))

TIFFErrorExt(tif->tif_clientdata, module,

"%s data at scanline %lu (%I64u != %I64u)",

npixels < maxpixels ? "Not enough" : "Too much",

(unsigned long) tif->tif_row,

(unsigned __int64) npixels,

(unsigned __int64) maxpixels);

#else

TIFFErrorExt(tif->tif_clientdata, module,

"%s data at scanline %lu (%llu != %llu)",

npixels < maxpixels ? "Not enough" : "Too much",

(unsigned long) tif->tif_row,

(unsigned long long) npixels,

(unsigned long long) maxpixels);

#endif

return (0);

}

return (1);

}

static int

ThunderDecodeRow(TIFF* tif, uint8* buf, tmsize_t occ, uint16 s)

{

static const char module[] = "ThunderDecodeRow";

uint8* row = buf;

(void) s;

if (occ % tif->tif_scanlinesize)

{

TIFFErrorExt(tif->tif_clientdata, module, "Fractional scanlines cannot be read");

return (0);

}

while (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_setupdecode = ThunderSetupDecode;

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:

*/