308 lines
8.0 KiB
C
308 lines
8.0 KiB
C
/* hough transform for circles
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*
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* 7/3/14
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* - from hough_line.c
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* 2/1/18
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* - 20% speedup
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*/
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/*
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This file is part of VIPS.
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VIPS is free software; you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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02110-1301 USA
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*/
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/*
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These files are distributed with VIPS - http://www.vips.ecs.soton.ac.uk
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*/
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/* Derived in part from David Young's Matlab circle detector:
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*
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* http://www.mathworks.com/matlabcentral/fileexchange/26978-hough-transform-for-circles
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*/
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#ifdef HAVE_CONFIG_H
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#include <config.h>
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#endif /*HAVE_CONFIG_H*/
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#include <glib/gi18n-lib.h>
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#include <string.h>
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#include <vips/vips.h>
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#include <vips/internal.h>
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#include "statistic.h"
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#include "hough.h"
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typedef struct _VipsHoughCircle {
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VipsHough parent_instance;
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int scale;
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int min_radius;
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int max_radius;
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int width;
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int height;
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int bands;
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} VipsHoughCircle;
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typedef VipsHoughClass VipsHoughCircleClass;
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G_DEFINE_TYPE( VipsHoughCircle, vips_hough_circle, VIPS_TYPE_HOUGH );
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/* Smaller circles have fewer pixels and therefore fewer votes. Scale bands by
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* the ratio of circumference, so all radii get equal weight.
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*/
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static void
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vips_hough_circle_normalise( VipsHoughCircle *hough_circle )
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{
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VipsHough *hough = (VipsHough *) hough_circle;
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int max_radius = hough_circle->max_radius;
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int min_radius = hough_circle->min_radius;
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int scale = hough_circle->scale;
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int bands = hough_circle->bands;
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int width = hough_circle->width;
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int height = hough_circle->height;
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double max_circumference = 2 * VIPS_PI * max_radius;
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int b;
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for( b = 0; b < bands; b++ ) {
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int radius = b * scale + min_radius;
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double circumference = 2 * VIPS_PI * radius;
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double ratio = max_circumference / circumference;
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size_t n_pels = (size_t) width * height * bands;
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size_t i;
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guint *q;
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q = b + (guint *) VIPS_IMAGE_ADDR( hough->out, 0, 0 );
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for( i = 0; i < n_pels; i += bands )
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q[i] *= ratio;
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}
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}
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static int
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vips_hough_circle_build( VipsObject *object )
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{
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VipsObjectClass *class = VIPS_OBJECT_GET_CLASS( object );
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VipsStatistic *statistic = (VipsStatistic *) object;
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VipsHoughCircle *hough_circle = (VipsHoughCircle *) object;
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int range = hough_circle->max_radius - hough_circle->min_radius;
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if( range <= 0 ) {
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vips_error( class->nickname,
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"%s", _( "parameters out of range" ) );
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return( -1 );
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}
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hough_circle->width = statistic->in->Xsize / hough_circle->scale;
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hough_circle->height = statistic->in->Ysize / hough_circle->scale;
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hough_circle->bands = 1 + range / hough_circle->scale;
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if( VIPS_OBJECT_CLASS( vips_hough_circle_parent_class )->
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build( object ) )
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return( -1 );
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vips_hough_circle_normalise( hough_circle );
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return( 0 );
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}
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static int
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vips_hough_circle_init_accumulator( VipsHough *hough, VipsImage *accumulator )
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{
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VipsHoughCircle *hough_circle = (VipsHoughCircle *) hough;
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vips_image_init_fields( accumulator,
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hough_circle->width, hough_circle->height, hough_circle->bands,
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VIPS_FORMAT_UINT, VIPS_CODING_NONE,
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VIPS_INTERPRETATION_MATRIX,
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1.0, 1.0 );
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return( 0 );
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}
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/* Vote endpoints, with clip.
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*/
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static void
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vips_hough_circle_vote_endpoints_clip( VipsImage *image,
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int y, int x1, int x2, int quadrant, void *client )
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{
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int r = *((int *) client);
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int b = image->Bands;
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if( y >= 0 &&
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y < image->Ysize ) {
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guint *line = (guint *) VIPS_IMAGE_ADDR( image, 0, y ) + r;
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if( x1 >=0 &&
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x1 < image->Xsize )
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line[x1 * b] += 1;
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if( x2 >=0 &&
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x2 < image->Xsize )
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line[x2 * b] += 1;
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}
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}
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/* Vote endpoints, no clip.
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*/
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static void
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vips_hough_circle_vote_endpoints_noclip( VipsImage *image,
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int y, int x1, int x2, int quadrant, void *client )
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{
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int r = *((int *) client);
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guint *line = (guint *) VIPS_IMAGE_ADDR( image, 0, y ) + r;
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int b = image->Bands;
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line[x1 * b] += 1;
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line[x2 * b] += 1;
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}
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/* Cast votes for all possible circles passing through x, y.
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*/
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static void
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vips_hough_circle_vote( VipsHough *hough, VipsImage *accumulator, int x, int y )
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{
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VipsHoughCircle *hough_circle = (VipsHoughCircle *) hough;
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int min_radius = hough_circle->min_radius;
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int cx = x / hough_circle->scale;
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int cy = y / hough_circle->scale;
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int rb;
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g_assert( hough_circle->max_radius - min_radius >= 0 );
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for( rb = 0; rb < hough_circle->bands; rb++ ) {
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/* r needs to be in scaled down image space.
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*/
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int r = rb + min_radius / hough_circle->scale;
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VipsDrawScanline draw_scanline;
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if( cx - r >= 0 &&
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cx + r < accumulator->Xsize &&
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cy - r >= 0 &&
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cy + r < accumulator->Ysize )
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draw_scanline = vips_hough_circle_vote_endpoints_noclip;
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else
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draw_scanline = vips_hough_circle_vote_endpoints_clip;
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vips__draw_circle_direct( accumulator,
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cx, cy, r, draw_scanline, &rb );
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}
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}
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static void
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vips_hough_circle_class_init( VipsHoughClass *class )
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{
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GObjectClass *gobject_class = (GObjectClass *) class;
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VipsObjectClass *object_class = (VipsObjectClass *) class;
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VipsHoughClass *hclass = (VipsHoughClass *) class;
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gobject_class->set_property = vips_object_set_property;
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gobject_class->get_property = vips_object_get_property;
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object_class->nickname = "hough_circle";
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object_class->description = _( "find hough circle transform" );
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object_class->build = vips_hough_circle_build;
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hclass->init_accumulator = vips_hough_circle_init_accumulator;
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hclass->vote = vips_hough_circle_vote;
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VIPS_ARG_INT( class, "scale", 119,
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_( "Scale" ),
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_( "Scale down dimensions by this factor" ),
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VIPS_ARGUMENT_OPTIONAL_INPUT,
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G_STRUCT_OFFSET( VipsHoughCircle, scale ),
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1, 100000, 3 );
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VIPS_ARG_INT( class, "min_radius", 120,
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_( "Min radius" ),
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_( "Smallest radius to search for" ),
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VIPS_ARGUMENT_OPTIONAL_INPUT,
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G_STRUCT_OFFSET( VipsHoughCircle, min_radius ),
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1, 100000, 10 );
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VIPS_ARG_INT( class, "max_radius", 121,
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_( "Max radius" ),
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_( "Largest radius to search for" ),
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VIPS_ARGUMENT_OPTIONAL_INPUT,
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G_STRUCT_OFFSET( VipsHoughCircle, max_radius ),
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1, 100000, 20 );
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}
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static void
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vips_hough_circle_init( VipsHoughCircle *hough_circle )
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{
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hough_circle->scale = 1;
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hough_circle->min_radius = 10;
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hough_circle->max_radius = 20;
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}
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/**
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* vips_hough_circle: (method)
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* @in: input image
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* @out: (out): output image
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* @...: %NULL-terminated list of optional named arguments
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*
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* Optional arguments:
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*
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* * @scale: scale down dimensions by this much
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* * @min_radius: smallest radius to search for
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* * @max_radius: largest radius to search for
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*
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* Find the circular Hough transform of an image. @in must be one band, with
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* non-zero pixels for image edges. @out is three-band, with the third channel
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* representing the detected circle radius. The operation scales the number of
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* votes by circle circumference so circles of differing size are given equal
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* weight.
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*
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* The output pixel at (x, y, band) is the strength of the circle centred on
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* (x, y) and with radius (band).
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*
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* Use @max_radius and @min_radius to set the range of radii to search for.
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*
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* Use @scale to set how @in coordinates are scaled to @out coordinates. A
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* @scale of 3, for example, will make @out 1/3rd of the width and height of
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* @in, and reduce the number of radii tested (and hence the number of bands
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* int @out) by a factor of three as well.
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*
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* See also: vips_hough_line().
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*
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* Returns: 0 on success, -1 on error
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*/
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int
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vips_hough_circle( VipsImage *in, VipsImage **out, ... )
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{
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va_list ap;
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int result;
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va_start( ap, out );
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result = vips_call_split( "hough_circle", ap, in, out );
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va_end( ap );
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return( result );
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}
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