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/* $XConsortium: epackbits.c,v 1.1 94/11/08 19:54:40 mor Exp $ */
/*
* Copyright (c) 1988, 1989, 1990, 1991, 1992 Sam Leffler
* Copyright (c) 1991, 1992 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 "lbximage.h"
/*
* -------------------------------------------------------------------------
* PackBits encoding for 8 bit color images
* -------------------------------------------------------------------------
*/
#define PutByte(byte,bufptr,bytesLeft) \
{ \
if (*bytesLeft < 1) {\
*outbuf = outptr; \
return (0); \
} \
*bufptr++ = byte; \
(*bytesLeft)--; \
}
static int
EncodePackBits (inbuf, numPixels, outbuf, bytesLeft)
char *inbuf;
int numPixels;
char **outbuf;
int *bytesLeft;
{
register int pixelsLeft = numPixels;
register char *outptr = *outbuf;
register char *lastliteral;
register int n, b;
enum { BASE, LITERAL, RUN, LITERAL_RUN } state;
int slop;
state = BASE;
lastliteral = 0;
while (pixelsLeft > 0)
{
/*
* Find the longest string of identical bytes.
*/
b = *inbuf++, pixelsLeft--, n = 1;
for (; pixelsLeft > 0 && b == *inbuf; pixelsLeft--, inbuf++)
n++;
again:
switch (state)
{
case BASE: /* initial state, set run/literal */
if (n > 1)
{
state = RUN;
if (n > 128)
{
PutByte (-127, outptr, bytesLeft);
PutByte (b, outptr, bytesLeft);
n -= 128;
goto again;
}
PutByte (-(n-1), outptr, bytesLeft);
PutByte (b, outptr, bytesLeft);
}
else
{
lastliteral = outptr;
PutByte (0, outptr, bytesLeft);
PutByte (b, outptr, bytesLeft);
state = LITERAL;
}
break;
case LITERAL: /* last object was literal string */
if (n > 1)
{
state = LITERAL_RUN;
if (n > 128)
{
PutByte (-127, outptr, bytesLeft);
PutByte (b, outptr, bytesLeft);
n -= 128;
goto again;
}
PutByte (-(n-1), outptr, bytesLeft); /* encode run */
PutByte (b, outptr, bytesLeft);
}
else
{ /* extend literal */
if (++(*lastliteral) == 127)
state = BASE;
PutByte (b, outptr, bytesLeft);
}
break;
case RUN: /* last object was run */
if (n > 1)
{
if (n > 128)
{
PutByte (-127, outptr, bytesLeft);
PutByte (b, outptr, bytesLeft);
n -= 128;
goto again;
}
PutByte (-(n-1), outptr, bytesLeft);
PutByte (b, outptr, bytesLeft);
}
else
{
lastliteral = outptr;
PutByte (0, outptr, bytesLeft);
PutByte (b, outptr, bytesLeft);
state = LITERAL;
}
break;
case LITERAL_RUN: /* literal followed by a run */
/*
* Check to see if previous run should
* be converted to a literal, in which
* case we convert literal-run-literal
* to a single literal.
*/
if (n == 1 && outptr[-2] == (char)-1 && *lastliteral < 126)
{
state = (((*lastliteral) += 2) == 127 ? BASE : LITERAL);
outptr[-2] = outptr[-1]; /* replicate */
}
else
state = RUN;
goto again;
}
}
*outbuf = outptr;
return (1);
}
int
LbxImageEncodePackBits (inbuf, outbuf, outbufSize,
num_scan_lines, scan_line_size, bytesCompressed)
char *inbuf;
char *outbuf;
int outbufSize;
int num_scan_lines;
int scan_line_size;
int *bytesCompressed;
{
char *outbuf_start = outbuf;
int padded_scan_line_size = (scan_line_size % 4) ?
scan_line_size + (4 - scan_line_size % 4) : scan_line_size;
int bytesLeft = outbufSize;
while (num_scan_lines > 0)
{
if (!EncodePackBits (inbuf, scan_line_size, &outbuf, &bytesLeft))
return (LBX_IMAGE_COMPRESS_NOT_WORTH_IT);
inbuf += padded_scan_line_size;
num_scan_lines--;
}
*bytesCompressed = outbuf - outbuf_start;
return (LBX_IMAGE_COMPRESS_SUCCESS);
}
|
