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More improvements in mars_decompress()

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git-svn-id: https://svn.code.sf.net/p/gphoto/code/trunk/libgphoto2@9122 67ed7778-7388-44ab-90cf-0a291f65f57c
This commit is contained in:
Theodore Kilgore
2006-08-29 00:17:35 +00:00
parent 817697c906
commit 2fd352e5af
1 changed files with 63 additions and 22 deletions
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85
camlibs/mars/mars.c
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@@ -200,22 +200,22 @@ void precalc_table(code_table_t *table)
}
else if ((i & 0xF0) == 0x80) {
/* code 1000 */
val = +8;
val = +7;
len = 4;
}
else if ((i & 0xF0) == 0x90) {
/* code 1001 */
val = -8;
val = -7;
len = 4;
}
else if ((i & 0xF0) == 0xF0) {
/* code 1111 */
val = -20;
val = -15;
len = 4;
}
else if ((i & 0xF8) == 0xE0) {
/* code 11100 */
val = +20;
val = +15;
len = 5;
}
else if ((i & 0xF8) == 0xE8) {
@@ -230,7 +230,13 @@ void precalc_table(code_table_t *table)
}
}
#define CLAMP(x) ((x)<16?16:((x)>251)?251:(x))
#define CLAMP(x) ((x)<20?20:((x)>255)?255:(x))
/* #define MAX(a,b) ((a)>(b)?(a):(b)) */
/* #define MIN(a,b) ((a)<(b)?(a):(b)) */
#define MAX3(a,b,c) MAX(MAX(a,b),c)
#define MIN3(a,b,c) MIN(MIN(a,b),c)
#define MAX4(a,b,c,d) MAX(MAX(a,b),MAX(c,d))
#define MIN4(a,b,c,d) MIN(MIN(a,b),MIN(c,d))
int mars_decompress (unsigned char *inp,
@@ -241,7 +247,7 @@ int mars_decompress (unsigned char *inp,
int val;
code_table_t table[256];
unsigned char *addr;
int bitpos;
int bitpos, i;
unsigned char A,B,C,D, predictor;
/* First calculate the Huffman table */
precalc_table(table);
@@ -293,10 +299,23 @@ int mars_decompress (unsigned char *inp,
}
else if (col < 2) {
/* left column: relative to top pixel */
val += (outp[-2*width] +
outp[-2*width + 2])/2;
/* initial estimate */
predictor = (outp[-2*width] +
outp[-2*width + 2])/2;
/* corrections */
if (row > 3) {
B=outp[-2*width ];
C=outp[-4*width ];
if (MAX((predictor -2*B+C),
(-predictor +2*B-C))
< 1)
predictor =
(7*predictor + C)/8;
}
val += predictor;
}
else if (col > width - 3) {
/* left column: relative to top pixel */
val += (outp[-2*width] +
@@ -309,19 +328,38 @@ int mars_decompress (unsigned char *inp,
C=outp[-2*width-2];
B=outp[-2*width ];
D=outp[-2*width+2];
if (D-A >= 0)
predictor=
MIN((D-A)/8, 251-(A+B)/2)+ (A+B)/2;
else
predictor=
-MIN((A-D)/8, (A+B)/2-4)+ (A+B)/2;
if ((val)&&(predictor > 0xcf))
val = (5*val +1)/4;
if ((val)&&(predictor < 0x20))
val = (5*val+3)/4;
val += predictor;
/* initial estimate for predictor */
predictor = (2*A + B + D+1)/4;
/* possible vertical edge? */
if (4*MAX((C -2*B + D),
(-C + 2*B - D)) < 1)
predictor =
(3*predictor + D+1)/4;
/* or horizontal edge? */
if (row >= 4) {
D=outp[-4*width - 2];
if (4*MAX((A -2*C + D),
(-A + 2*C - D)) < 1)
predictor =
(3*predictor + A+1)/4;
}
/* decrease changes for close values */
if (MAX3(A,B,D) - MIN3(A,B,D)
< 0x20) {
if(val > 0)
val -= 1;
if (val < 0)
val += 1;
}
/* increase change for widespread values*/
if (MAX4(A,B,C,D) - MIN4(A,B,C,D)
> 0x30) {
if(val > 0)
val += 1;
if (val < 0)
val -= 1;
}
val += predictor;
}
}
@@ -330,6 +368,9 @@ int mars_decompress (unsigned char *inp,
col++;
}
}
/* spread the clamped values upward */
// for (i=0; i< sizeof(outp); i++)
// outp[i] = outp[i]*255/236;
return 0;
}