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fix an off-by-one error in hist_local

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an odd window width caused an off-by-one error in histogram construction
This commit is contained in:
John Cupitt 2017-01-24 10:51:12 +00:00
parent 36761bcfd7
commit c9ce8f70a1
2 changed files with 5 additions and 4 deletions
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2
ChangeLog
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@ -27,7 +27,7 @@
aferrero2707
- kick load operations from cache on read error, thanks gaillard
- fix return from C++ assignment operator overloads (+=, -= etc)
- add @max_slope to vips_local_hist() to implement CLAHE, thanks hunter-87
- add @max_slope to vips_hist_local() to implement CLAHE, thanks hunter-87
- vips_gaussnoise() pixels are reproducible on recalc, thanks MvGulik
8/12/16 started 8.4.5

7
libvips/histogram/hist_local.c
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@ -26,6 +26,7 @@
* - sum to <= target, not < target, since cumulative hists include the
* current value
* - scale result by 255, not 256, to avoid overflow
* - off by 1 fix for odd window widths
*/
/*
@ -150,7 +151,8 @@ vips_hist_local_generate( VipsRegion *or,
VipsImage *in = (VipsImage *) a;
const VipsHistLocal *local = (VipsHistLocal *) b;
VipsRect *r = &or->valid;
int bands = in->Bands;
const int bands = in->Bands;
const int max_slope = local->max_slope;
VipsRect irect;
int y;
@ -167,7 +169,7 @@ vips_hist_local_generate( VipsRegion *or,
return( -1 );
lsk = VIPS_REGION_LSKIP( seq->ir );
centre = lsk * (local->height / 2) + bands * local->width / 2;
centre = lsk * (local->height / 2) + bands * (local->width / 2);
for( y = 0; y < r->height; y++ ) {
/* Get input and output pointers for this line.
@ -201,7 +203,6 @@ vips_hist_local_generate( VipsRegion *or,
*/
unsigned int * restrict hist = seq->hist[b];
const int target = p[centre + b];
const int max_slope = local->max_slope;
int sum;