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normalise hough_circle output

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correct for number of pixels in circumference
This commit is contained in:
John Cupitt 2014-04-01 19:39:10 +01:00
parent 59b36f8351
commit fb24bc84d3
2 changed files with 46 additions and 15 deletions
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14
TODO
View File

@ -6,20 +6,6 @@
- vips_hough_circle() params need fixing
we need to give a "scale" param which sets width/height of acc as a
factor of original
min_radius / max_radius set range of circles to search for
number of bands in acc image is range / scale
width/height need to move out of hough.c into hough_line.c: they only make
sense for that param space
- ink to vec etc must have a way to give a complex constant
eg. drawink needs a --ink_imag option with the imaginary components of the

47
libvips/arithmetic/hough_circle.c
View File

@ -61,6 +61,42 @@ typedef VipsHoughClass VipsHoughCircleClass;
G_DEFINE_TYPE( VipsHoughCircle, vips_hough_circle, VIPS_TYPE_HOUGH );
/* Smaller circles have fewer pixels and therefore fewer votes. Scale bands by
* the ratio of circumference, so all radii get equal weight.
*/
static void
vips_hough_circle_normalise( VipsHoughCircle *hough_circle )
{
VipsHough *hough = (VipsHough *) hough_circle;
int max_radius = hough_circle->max_radius;
int min_radius = hough_circle->min_radius;
int scale = hough_circle->scale;
int bands = hough_circle->bands;
int width = hough_circle->width;
int height = hough_circle->height;
double max_circumference = 2 * VIPS_PI * max_radius;
int b;
for( b = 0; b < bands; b++ ) {
int radius = b * scale + min_radius;
double circumference = 2 * VIPS_PI * radius;
double ratio = max_circumference / circumference;
int x, y;
guint *q;
q = b + (guint *) VIPS_IMAGE_ADDR( hough->out, 0, 0 );
for( y = 0; y < height; y++ ) {
for( x = 0; x < width; x++ )
*q *= ratio;
q += bands;
}
}
}
static int
vips_hough_circle_build( VipsObject *object )
{
@ -83,6 +119,8 @@ vips_hough_circle_build( VipsObject *object )
build( object ) )
return( -1 );
vips_hough_circle_normalise( hough_circle );
return( 0 );
}
@ -240,7 +278,14 @@ vips_hough_circle_init( VipsHoughCircle *hough_circle )
* @min_radius: smallest radius to search for
* @max_radius: largest radius to search for
*
* See also:
* Find the circular Hough transform of an image. @in must be one band, with
* non-zero pixels for image edges. @out is three-band, with the third channel
* representing the detected circle radius.
*
*
*
*
* See also: vips_hough_line().
*
* Returns: 0 on success, -1 on error
*/