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use a LUT for hough sin/cos

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This commit is contained in:
John Cupitt 2014-03-24 19:45:03 +00:00
parent 9a1fa499f5
commit 4d758af087
1 changed files with 36 additions and 6 deletions
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42
libvips/arithmetic/hough_line.c
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@ -43,11 +43,39 @@
#include "statistic.h"
#include "hough.h"
typedef VipsHough VipsHoughLine;
typedef struct _VipsHoughLine {
VipsHough parent_instance;
/* LUT for this transform.
*/
double *sin;
} VipsHoughLine;
typedef VipsHoughClass VipsHoughLineClass;
G_DEFINE_TYPE( VipsHoughLine, vips_hough_line, VIPS_TYPE_HOUGH );
static int
vips_hough_line_build( VipsObject *object )
{
VipsHough *hough = (VipsHough *) object;
VipsHoughLine *hough_line = (VipsHoughLine *) object;
int i;
if( !(hough_line->sin = VIPS_ARRAY( object, hough->width, double )) )
return( -1 );
for( i = 0; i < hough->width; i++ )
hough_line->sin[i] = sin( 2 * M_PI * i / hough->width );
if( VIPS_OBJECT_CLASS( vips_hough_line_parent_class )->build( object ) )
return( -1 );
return( 0 );
}
/* Build a new accumulator.
*/
static VipsImage *
@ -76,20 +104,21 @@ vips_hough_line_new_accumulator( VipsHough *hough )
static void
vips_hough_line_vote( VipsHough *hough, VipsImage *accumulator, int x, int y )
{
VipsHoughLine *hough_line = (VipsHoughLine *) hough;
VipsStatistic *statistic = (VipsStatistic *) hough;
double xd = (double) x / statistic->ready->Xsize;
double yd = (double) y / statistic->ready->Ysize;
int thetai;
int i;
for( thetai = 0; thetai < hough->width; thetai++ ) {
double theta = 2 * M_PI * thetai / hough->width;
double r = xd * cos( theta ) + yd * sin( theta );
for( i = 0; i < hough->width; i++ ) {
int i90 = (i + hough->width / 4) % hough->width;
double r = xd * hough_line->sin[i90] + yd * hough_line->sin[i];
int ri = hough->height * r;
if( ri >= 0 &&
ri < hough->height )
*VIPS_IMAGE_ADDR( accumulator, thetai, ri ) += 1;
*VIPS_IMAGE_ADDR( accumulator, i, ri ) += 1;
}
}
@ -101,6 +130,7 @@ vips_hough_line_class_init( VipsHoughClass *class )
object_class->nickname = "hough_line";
object_class->description = _( "find hough line transform" );
object_class->build = vips_hough_line_build;
hclass->new_accumulator = vips_hough_line_new_accumulator;
hclass->vote = vips_hough_line_vote;