606 lines
13 KiB
C
606 lines
13 KiB
C
/* Canny edge detector
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*
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* 2/2/18
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* - from vips_canny()
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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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/*
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#define DEBUG
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*/
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/* TODO
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* - verify that our interpolating max edge works
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* - does it actually help much?
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* - can skip the sqrt()
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* - support other image types
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* - swap atan2 for a LUT with perhaps +/- 2 or 4 bits
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* - check sobel speed with separated and non-sep masks
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* - add autothreshold with otsu's method
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* - leave blob analysis to a separate pass
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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 <vips/intl.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <math.h>
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#include <vips/vips.h>
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typedef struct _VipsCanny {
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VipsOperation parent_instance;
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VipsImage *in;
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VipsImage *out;
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double sigma;
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gboolean interpolate;
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double low;
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double high;
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/* Need an image vector for start_many.
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*/
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VipsImage *args[3];
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} VipsCanny;
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typedef VipsOperationClass VipsCannyClass;
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G_DEFINE_TYPE( VipsCanny, vips_canny, VIPS_TYPE_OPERATION );
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/* Simple 2x2 -1/+1 difference.
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*/
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static int
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vips_canny_gradient_simple( VipsImage *in, VipsImage **Gx, VipsImage **Gy )
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{
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VipsImage *scope;
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VipsImage **t;
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scope = vips_image_new();
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t = (VipsImage **) vips_object_local_array( (VipsObject *) scope, 20 );
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t[1] = vips_image_new_matrixv( 2, 2,
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-1.0, 1.0,
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-1.0, 1.0 );
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vips_image_set_double( t[1], "offset", 128.0 );
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if( vips_conv( in, Gx, t[1],
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"precision", VIPS_PRECISION_INTEGER,
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NULL ) ) {
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g_object_unref( scope );
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return( -1 );
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}
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t[5] = vips_image_new_matrixv( 2, 2,
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-1.0, -1.0,
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1.0, 1.0 );
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vips_image_set_double( t[5], "offset", 128.0 );
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if( vips_conv( in, Gy, t[5],
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"precision", VIPS_PRECISION_INTEGER,
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NULL ) ) {
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g_object_unref( scope );
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return( -1 );
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}
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g_object_unref( scope );
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return( 0 );
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}
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static int
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vips_canny_polar_generate( VipsRegion *or,
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void *vseq, void *a, void *b, gboolean *stop )
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{
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VipsRegion **in = (VipsRegion **) vseq;
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VipsRect *r = &or->valid;
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VipsImage *Gx = in[0]->im;
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int x, y, band;
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if( vips_reorder_prepare_many( or->im, in, r ) )
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return( -1 );
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for( y = 0; y < r->height; y++ ) {
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VipsPel *p1 = (VipsPel * restrict)
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VIPS_REGION_ADDR( in[0], r->left, r->top + y );
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VipsPel *p2 = (VipsPel * restrict)
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VIPS_REGION_ADDR( in[1], r->left, r->top + y );
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VipsPel *q = (VipsPel * restrict)
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VIPS_REGION_ADDR( or, r->left, r->top + y );
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for( x = 0; x < r->width; x++ ) {
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for( band = 0; band < Gx->Bands; band++ ) {
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int x = p1[band] - 128;
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int y = p2[band] - 128;
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int a = VIPS_DEG( atan2( x, y ) ) + 360;
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/* We should calculate
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* 0.5 * sqrt( x * x + y * y )
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* ie. length of hypot, scaled down to avoid
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* clipping. We are only interested in relative
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* magnitude, so we can skip the sqrt and just
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* shift down 9 bits.
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*/
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q[0] = (x * x + y * y + 256) >> 9;
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q[1] = 256 * a / 360;
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q += 2;
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}
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p1 += Gx->Bands;
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p2 += Gx->Bands;
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}
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}
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return( 0 );
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}
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/* Calculate G/theta from Gx/Gy -- rather like rect -> polar, except that we
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* code theta as below. Scale G down by 0.5 so that we
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* don't clip on hard edges.
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*
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* For a white disc on a black background, theta is 0 at the bottom, 64 on the
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* right, 128 at the top and 192 on the left edge.
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*/
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static int
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vips_canny_polar( VipsImage **args, VipsImage **out )
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{
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*out = vips_image_new();
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if( vips_image_pipeline_array( *out,
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VIPS_DEMAND_STYLE_THINSTRIP, args ) )
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return( -1 );
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(*out)->Bands *= 2;
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if( vips_image_generate( *out,
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vips_start_many, vips_canny_polar_generate, vips_stop_many,
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args, NULL ) )
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return( -1 );
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return( 0 );
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}
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static int
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vips_canny_nonmax_generate( VipsRegion *or,
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void *vseq, void *a, void *b, gboolean *stop )
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{
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VipsRegion *in = (VipsRegion *) vseq;
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VipsRect *r = &or->valid;
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VipsImage *im = in->im;
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int out_bands = or->im->Bands;
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VipsRect rect;
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int x, y, band;
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int lsk;
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int psk;
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int offseta[4];
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int offsetb[4];
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rect = *r;
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rect.width += 2;
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rect.height += 2;
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if( vips_region_prepare( in, &rect ) )
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return( -1 );
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lsk = VIPS_REGION_LSKIP( in );
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psk = VIPS_IMAGE_SIZEOF_PEL( im );
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/* For each of the four directions, the offset to get to that pixel
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* from the top-left of our 3x3. offseta is the left/up direction, or
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* the lower memory address.
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*
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* 1 | 0 | 3
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* --+---+--
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* 2 | X | 2
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* --+---+--
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* 3 | 0 | 1
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*/
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offseta[0] = psk;
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offsetb[0] = psk + 2 * lsk;
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offseta[1] = 0;
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offsetb[1] = 2 * psk + 2 * lsk;
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offseta[2] = lsk;
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offsetb[2] = 2 * psk + lsk;
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offseta[3] = 2 * psk;
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offsetb[3] = 2 * lsk;
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for( y = 0; y < r->height; y++ ) {
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VipsPel *p = (VipsPel * restrict)
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VIPS_REGION_ADDR( in, r->left, r->top + y );
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VipsPel *q = (VipsPel * restrict)
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VIPS_REGION_ADDR( or, r->left, r->top + y );
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for( x = 0; x < r->width; x++ ) {
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for( band = 0; band < out_bands; band++ ) {
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int G = p[lsk + psk];
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int theta = p[lsk + psk + 1];
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int a = ((theta + 16) / 32) & 0x3;
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VipsPel low = p[offseta[a]];
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VipsPel high = p[offsetb[a]];
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/* Set G to 0 if it's not the local maxima in
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* the direction of the gradient. If G is equal
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* to the low side, also zero, so wide edges
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* with equal gradient move (arbitarilly) left
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* and up.
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*/
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if( G <= low ||
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G < high )
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G = 0;
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q[band] = G;
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p += 2;
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}
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q += out_bands;
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}
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}
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return( 0 );
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}
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/* Remove non-maximal edges. At each point, compare the G to the G in either
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* direction and 0 it if it's not the largest.
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*/
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static int
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vips_canny_nonmax( VipsImage *in, VipsImage **out )
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{
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*out = vips_image_new();
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if( vips_image_pipelinev( *out,
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VIPS_DEMAND_STYLE_THINSTRIP, in, NULL ) )
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return( -1 );
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(*out)->Bands /= 2;
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(*out)->Xsize -= 2;
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(*out)->Ysize -= 2;
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if( vips_image_generate( *out,
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vips_start_one, vips_canny_nonmax_generate, vips_stop_one,
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in, NULL ) )
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return( -1 );
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return( 0 );
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}
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static int
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vips_canny_nonmaxi_generate( VipsRegion *or,
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void *vseq, void *a, void *b, gboolean *stop )
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{
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VipsRegion *in = (VipsRegion *) vseq;
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VipsRect *r = &or->valid;
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VipsImage *im = in->im;
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int out_bands = or->im->Bands;
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VipsRect rect;
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int x, y, band;
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int lsk;
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int psk;
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int offset[8];
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rect = *r;
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rect.width += 2;
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rect.height += 2;
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if( vips_region_prepare( in, &rect ) )
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return( -1 );
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lsk = VIPS_REGION_LSKIP( in );
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psk = VIPS_IMAGE_SIZEOF_PEL( im );
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/* For each of the 8 directions, the offset to get to that pixel from
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* the top-left of the 3x3.
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*
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* 5 | 4 | 3
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* --+---+--
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* 6 | X | 2
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* --+---+--
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* 7 | 0 | 1
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*/
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offset[0] = psk + 2 * lsk;
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offset[1] = 2 * psk + 2 * lsk;
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offset[2] = 2 * psk + lsk;
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offset[3] = 2 * psk;
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offset[4] = psk;
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offset[5] = 0;
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offset[6] = lsk;
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offset[7] = 2 * lsk;
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for( y = 0; y < r->height; y++ ) {
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VipsPel *p = (VipsPel * restrict)
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VIPS_REGION_ADDR( in, r->left, r->top + y );
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VipsPel *q = (VipsPel * restrict)
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VIPS_REGION_ADDR( or, r->left, r->top + y );
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for( x = 0; x < r->width; x++ ) {
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for( band = 0; band < out_bands; band++ ) {
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int G = p[lsk + psk];
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int theta = p[lsk + psk + 1];
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int low_theta = (theta / 32) & 0x7;
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int high_theta = (low_theta + 1) & 0x7;
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int residual = theta - low_theta * 32;
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int lowa = p[offset[low_theta]];
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int lowb = p[offset[high_theta]];
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int low = (lowa * (32 - residual) +
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lowb * residual) / 32;
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int higha = p[offset[(low_theta + 4) & 0x7]];
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int highb = p[offset[(high_theta + 4) & 0x7]];
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int high = (higha * (32 - residual) +
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highb * residual) / 32;
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/* Set G to 0 if it's not the local maxima in
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* the direction of the gradient.
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*/
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if( G <= low ||
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G < high )
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G = 0;
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q[band] = G;
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p += 2;
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}
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q += out_bands;
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}
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}
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return( 0 );
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}
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/* Remove non-maximal edges. At each point, compare the G to the G in either
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* direction and 0 it if it's not the largest.
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*/
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static int
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vips_canny_nonmaxi( VipsImage *in, VipsImage **out )
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{
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*out = vips_image_new();
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if( vips_image_pipelinev( *out,
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VIPS_DEMAND_STYLE_THINSTRIP, in, NULL ) )
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return( -1 );
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(*out)->Bands /= 2;
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(*out)->Xsize -= 2;
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(*out)->Ysize -= 2;
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if( vips_image_generate( *out,
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vips_start_one, vips_canny_nonmaxi_generate, vips_stop_one,
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in, NULL ) )
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return( -1 );
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return( 0 );
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}
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static int
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vips_canny_thresh_generate( VipsRegion *or,
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void *vseq, void *a, void *b, gboolean *stop )
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{
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VipsRegion *in = (VipsRegion *) vseq;
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VipsCanny *canny = (VipsCanny *) b;
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VipsRect *r = &or->valid;
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int sz = r->width * in->im->Bands;
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VipsPel low = canny->low;
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VipsPel high = canny->high;
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int x, y;
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if( vips_region_prepare( in, r ) )
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return( -1 );
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for( y = 0; y < r->height; y++ ) {
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VipsPel *p = (VipsPel * restrict)
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VIPS_REGION_ADDR( in, r->left, r->top + y );
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VipsPel *q = (VipsPel * restrict)
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VIPS_REGION_ADDR( or, r->left, r->top + y );
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for( x = 0; x < sz; x++ ) {
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int v;
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v = p[x];
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if( v <= low )
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v = 0;
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else if( v <= high )
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v = 128;
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else
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v = 255;
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q[x] = v;
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}
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}
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return( 0 );
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}
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static int
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vips_canny_thresh( VipsCanny *canny, VipsImage *in, VipsImage **out )
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{
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*out = vips_image_new();
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if( vips_image_pipelinev( *out,
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VIPS_DEMAND_STYLE_THINSTRIP, in, NULL ) )
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return( -1 );
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if( vips_image_generate( *out,
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vips_start_one, vips_canny_thresh_generate, vips_stop_one,
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in, canny ) )
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return( -1 );
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return( 0 );
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}
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static int
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vips_canny_build( VipsObject *object )
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{
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VipsCanny *canny = (VipsCanny *) object;
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VipsImage **t = (VipsImage **) vips_object_local_array( object, 20 );
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VipsImage *in;
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VipsImage *Gx;
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VipsImage *Gy;
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if( VIPS_OBJECT_CLASS( vips_canny_parent_class )->build( object ) )
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return( -1 );
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in = canny->in;
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if( vips_gaussblur( in, &t[0], canny->sigma, NULL ) )
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return( -1 );
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in = t[0];
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if( vips_canny_gradient_simple( in, &Gx, &Gy ) )
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return( -1 );
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/* Form (G, theta), with theta coded.
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*/
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canny->args[0] = Gx;
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canny->args[1] = Gy;
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canny->args[2] = NULL;
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if( vips_canny_polar( canny->args, &t[9] ) )
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return( -1 );
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in = t[9];
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/* Expand by two pixels all around, then thin.
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*/
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if( vips_embed( in, &t[10], 1, 1, in->Xsize + 2, in->Ysize + 2,
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"extend", VIPS_EXTEND_COPY,
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NULL ) )
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return( -1 );
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if( canny->interpolate ) {
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if( vips_canny_nonmaxi( t[10], &t[11] ) )
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return( -1 );
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}
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else {
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if( vips_canny_nonmax( t[10], &t[11] ) )
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return( -1 );
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}
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in = t[11];
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/* Double threshold.
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*/
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if( vips_canny_thresh( canny, in, &t[12] ) )
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return( -1 );
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in = t[12];
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g_object_set( object, "out", vips_image_new(), NULL );
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if( vips_image_write( in, canny->out ) )
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return( -1 );
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return( 0 );
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}
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static void
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vips_canny_class_init( VipsCannyClass *class )
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{
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GObjectClass *gobject_class = G_OBJECT_CLASS( class );
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VipsObjectClass *object_class = (VipsObjectClass *) class;
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VipsOperationClass *operation_class = VIPS_OPERATION_CLASS( 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 = "canny";
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object_class->description = _( "gaussian blur" );
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object_class->build = vips_canny_build;
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operation_class->flags = VIPS_OPERATION_SEQUENTIAL;
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|
|
VIPS_ARG_IMAGE( class, "in", 1,
|
|
_( "Input" ),
|
|
_( "Input image" ),
|
|
VIPS_ARGUMENT_REQUIRED_INPUT,
|
|
G_STRUCT_OFFSET( VipsCanny, in ) );
|
|
|
|
VIPS_ARG_IMAGE( class, "out", 2,
|
|
_( "Output" ),
|
|
_( "Output image" ),
|
|
VIPS_ARGUMENT_REQUIRED_OUTPUT,
|
|
G_STRUCT_OFFSET( VipsCanny, out ) );
|
|
|
|
VIPS_ARG_DOUBLE( class, "sigma", 10,
|
|
_( "Sigma" ),
|
|
_( "Sigma of Gaussian" ),
|
|
VIPS_ARGUMENT_OPTIONAL_INPUT,
|
|
G_STRUCT_OFFSET( VipsCanny, sigma ),
|
|
0.01, 1000, 1.4 );
|
|
|
|
VIPS_ARG_DOUBLE( class, "low", 11,
|
|
_( "Low" ),
|
|
_( "Low threshold" ),
|
|
VIPS_ARGUMENT_OPTIONAL_INPUT,
|
|
G_STRUCT_OFFSET( VipsCanny, low ),
|
|
-INFINITY, INFINITY, 3.0 );
|
|
|
|
VIPS_ARG_DOUBLE( class, "high", 12,
|
|
_( "High" ),
|
|
_( "High threshold" ),
|
|
VIPS_ARGUMENT_OPTIONAL_INPUT,
|
|
G_STRUCT_OFFSET( VipsCanny, high ),
|
|
-INFINITY, INFINITY, 7.0 );
|
|
|
|
VIPS_ARG_BOOL( class, "interpolate", 13,
|
|
_( "Interpolate" ),
|
|
_( "Interpolate gradient angles" ),
|
|
VIPS_ARGUMENT_OPTIONAL_INPUT,
|
|
G_STRUCT_OFFSET( VipsCanny, interpolate ),
|
|
FALSE );
|
|
|
|
}
|
|
|
|
static void
|
|
vips_canny_init( VipsCanny *canny )
|
|
{
|
|
canny->sigma = 1.4;
|
|
canny->low = 3.0;
|
|
canny->high = 7.0;
|
|
}
|
|
|
|
/**
|
|
* vips_canny: (method)
|
|
* @in: input image
|
|
* @out: (out): output image
|
|
* @sigma: how large a mask to use
|
|
* @...: %NULL-terminated list of optional named arguments
|
|
*
|
|
* Optional arguments:
|
|
*
|
|
* * @sigma: %gdouble, sigma for gaussian blur
|
|
*
|
|
* See also: vips_gaussblur().
|
|
*
|
|
* Returns: 0 on success, -1 on error.
|
|
*/
|
|
int
|
|
vips_canny( VipsImage *in, VipsImage **out, ... )
|
|
{
|
|
va_list ap;
|
|
int result;
|
|
|
|
va_start( ap, out );
|
|
result = vips_call_split( "canny", ap, in, out );
|
|
va_end( ap );
|
|
|
|
return( result );
|
|
}
|