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1) quantization stepsizes stored as float instead of shifted integers -> fixes a pb of precision when using very small stepsizes. 2) bug fixed when decoding until bitplane 0 -> r-value (1/2) added to the coefficient.

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This commit is contained in:
Antonin Descampe
2005-10-27 07:49:29 +00:00
parent 7f8f47566f
commit 7ee36c3a4c
4 changed files with 37 additions and 70 deletions
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15
codec/image_to_j2k.c
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@@ -250,12 +250,13 @@ int floorlog2(int a)
return l;
}
void encode_stepsize(int stepsize, int numbps, int *expn, int *mant)
void encode_stepsize(float stepsize, int numbps, int *expn, int *mant)
{
int p, n;
p = floorlog2(stepsize) - 13;
n = 11 - floorlog2(stepsize);
*mant = (n < 0 ? stepsize >> -n : stepsize << n) & 0x7ff;
int p, n, stepsizeTMP;
stepsizeTMP=(int) floor(stepsize * 8192.0);
p = floorlog2(stepsizeTMP) - 13;
n = 11 - floorlog2(stepsizeTMP);
*mant = (n < 0 ? stepsizeTMP >> -n : stepsizeTMP << n) & 0x7ff;
*expn = numbps - p;
}
@@ -264,7 +265,7 @@ void calc_explicit_stepsizes(j2k_tccp_t * tccp, int prec)
int numbands, bandno;
numbands = 3 * tccp->numresolutions - 2;
for (bandno = 0; bandno < numbands; bandno++) {
double stepsize;
float stepsize;
int resno, level, orient, gain;
resno = bandno == 0 ? 0 : (bandno - 1) / 3 + 1;
@@ -280,7 +281,7 @@ void calc_explicit_stepsizes(j2k_tccp_t * tccp, int prec)
double norm = dwt_norms_97[orient][level];
stepsize = (1 << (gain + 1)) / norm;
}
encode_stepsize((int) floor(stepsize * 8192.0), prec + gain,
encode_stepsize(stepsize, prec + gain,
&tccp->stepsizes[bandno].expn,
&tccp->stepsizes[bandno].mant);
}