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first hack

This commit is contained in:
John Cupitt 2017-01-20 14:59:24 +00:00
parent d05018155d
commit c89014fb3f
1 changed files with 55 additions and 6 deletions
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61
libvips/histogram/hist_local.c
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@ -21,6 +21,8 @@
* - redo as a class
* 9/9/13
* - any number of bands
* 20/1/17
* - add contrast limit
*/
/*
@ -71,6 +73,16 @@ typedef struct _VipsHistLocal {
int width;
int height;
double clip_limit;
/* width * height, ie. the area of the histogram we make.
*/
int area;
/* clip_limit * area, ie. relative to our maximum height.
*/
int clip;
} VipsHistLocal;
typedef VipsOperationClass VipsHistLocalClass;
@ -82,7 +94,7 @@ G_DEFINE_TYPE( VipsHistLocal, vips_hist_local, VIPS_TYPE_OPERATION );
typedef struct {
VipsRegion *ir; /* Input region */
/* A 256-element hist for evry band.
/* A 256-element hist for every band.
*/
unsigned int **hist;
} VipsHistLocalSequence;
@ -193,14 +205,38 @@ vips_hist_local_generate( VipsRegion *or,
*/
unsigned int *hist = seq->hist[b];
int target = p[centre];
int sum;
sum = 0;
for( i = 0; i < target; i++ )
sum += hist[i];
*q++ = 256 * sum /
(local->width * local->height);
/* For CLAHE we need to limit the height of the
* hist to limit the amount we boost the
* contrast by. If there's no limit, we can
* take a shorter path.
*/
if( local->clip_limit < 1.0 ) {
int sum_over;
sum_over = 0;
for( i = 0; i < 256; i++ ) {
if( hist[i] > local->clip )
sum_over += hist[i];
else
sum += hist[i];
}
sum += sum_over / 256;
}
else {
sum = 0;
for( i = 0; i < target; i++ )
sum += hist[i];
}
*q++ = 256 * sum / local->area;
/* Adapt histogram --- remove the pels from
* the left hand column, add in pels for a
@ -249,12 +285,16 @@ vips_hist_local_build( VipsObject *object )
return( -1 );
}
local->area = local->width * local->height;
local->clip = local->clip_limit * local->area;
/* Expand the input.
*/
if( vips_embed( in, &t[1],
local->width / 2, local->height / 2,
in->Xsize + local->width - 1, in->Ysize + local->height - 1,
"extend", VIPS_EXTEND_COPY,
"extend", VIPS_EXTEND_MIRROR,
NULL ) )
return( -1 );
in = t[1];
@ -323,11 +363,20 @@ vips_hist_local_class_init( VipsHistLocalClass *class )
VIPS_ARGUMENT_REQUIRED_INPUT,
G_STRUCT_OFFSET( VipsHistLocal, height ),
1, VIPS_MAX_COORD, 1 );
VIPS_ARG_DOUBLE( class, "clip_limit", 6,
_( "Clip limit" ),
_( "Clip the histogram at this height (CLAHE)" ),
VIPS_ARGUMENT_OPTIONAL_INPUT,
G_STRUCT_OFFSET( VipsHistLocal, clip_limit ),
0.0, 1.0, 1.0 );
}
static void
vips_hist_local_init( VipsHistLocal *local )
{
local->clip_limit = 1.0;
}
/**