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start adding canny

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just adding edge thinning

see https://en.wikipedia.org/wiki/Canny_edge_detector
This commit is contained in:
John Cupitt 2018-02-02 17:00:23 +00:00
parent ce1f236c4d
commit a93e8dd079
4 changed files with 348 additions and 0 deletions
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1
libvips/convolution/Makefile.am
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@ -1,6 +1,7 @@
noinst_LTLIBRARIES = libconvolution.la
libconvolution_la_SOURCES = \
canny.c \
convolution.c \
pconvolution.h \
correlation.c \

342
libvips/convolution/canny.c Normal file
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@ -0,0 +1,342 @@
/* Canny edge detector
*
* 2/2/18
* - from vips_canny()
*/
/*
This file is part of VIPS.
VIPS is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA
*/
/*
These files are distributed with VIPS - http://www.vips.ecs.soton.ac.uk
*/
/*
#define DEBUG
*/
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif /*HAVE_CONFIG_H*/
#include <vips/intl.h>
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <vips/vips.h>
typedef struct _VipsCanny {
VipsOperation parent_instance;
VipsImage *in;
VipsImage *out;
gdouble sigma;
/* Need an image vector for start_many.
*/
VipsImage *args[3];
} VipsCanny;
typedef VipsOperationClass VipsCannyClass;
G_DEFINE_TYPE( VipsCanny, vips_canny, VIPS_TYPE_OPERATION );
static int
vips_canny_polar_generate( VipsRegion *or,
void *vseq, void *a, void *b, gboolean *stop )
{
VipsRegion **in = (VipsRegion **) vseq;
VipsRect *r = &or->valid;
VipsImage *Gx = in[0]->im;
int x, y, band;
if( vips_reorder_prepare_many( or->im, in, r ) )
return( -1 );
for( y = 0; y < r->height; y++ ) {
VipsPel *p1 = (VipsPel * restrict)
VIPS_REGION_ADDR( in[0], r->left, r->top + y );
VipsPel *p2 = (VipsPel * restrict)
VIPS_REGION_ADDR( in[1], r->left, r->top + y );
VipsPel *q = (VipsPel * restrict)
VIPS_REGION_ADDR( or, r->left, r->top + y );
for( x = 0; x < r->width; x++ ) {
for( band = 0; band < Gx->Bands; band++ ) {
int x = p1[band] - 128;
int y = p2[band] - 128;
int a = VIPS_DEG( atan2( x, y ) );
q[0] = sqrt( x * x + y * y );
q[1] = ((a + 360 + 22) / 45) & 0x3;
q += 2;
}
p1 += Gx->Bands;
p2 += Gx->Bands;
}
}
return( 0 );
}
/* Calculate G/theta from Gx/Gy -- rather like rect -> polar, except that we
* constrain theta to 0/45/90/135, which we code as 0/1/2/3, and we don't care
* about the sign of G.
*
* Theta values:
*
* 3 | 0 | 1
* --+---+--
* 2 | x | 2
* --+---+--
* 1 | 0 | 3
*/
static int
vips_canny_polar( VipsImage **args, VipsImage **out )
{
*out = vips_image_new();
if( vips_image_pipeline_array( *out,
VIPS_DEMAND_STYLE_THINSTRIP, args ) )
return( -1 );
(*out)->Bands *= 2;
if( vips_image_generate( *out,
vips_start_many, vips_canny_polar_generate, vips_stop_many,
args, NULL ) )
return( -1 );
return( 0 );
}
static int
vips_canny_nonmax_generate( VipsRegion *or,
void *vseq, void *a, void *b, gboolean *stop )
{
VipsRegion *in = (VipsRegion *) vseq;
VipsRect *r = &or->valid;
VipsImage *im = in->im;
VipsRect rect;
int x, y, band;
int lsk;
int
rect = *r;
rect.width += 2;
rect.height += 2;
if( vips_region_prepare( in, &rect ) )
return( -1 );
lsk = VIPS_REGION_LSKIP( in );
for( y = 0; y < r->height; y++ ) {
VipsPel *p = (VipsPel * restrict)
VIPS_REGION_ADDR( in, r->left, r->top + y );
VipsPel *q = (VipsPel * restrict)
VIPS_REGION_ADDR( or, r->left, r->top + y );
for( x = 0; x < r->width; x++ ) {
for( band = 0; band < im->Bands; band++ ) {
int G = p[0];
int theta = p[1];
int v1, v2;
if( theta == 0 ) {
v1 = p[
switch( theta ) {
case 0:
q[band] = x;
p += 2;
}
q += im->Bands;
}
}
return( 0 );
}
/* Remove non-maximal edges. At each point, compare the G to the G in either
* direction and 0 it if it's not the largest.
*/
static int
vips_canny_nonmax( VipsImage *in, VipsImage **out )
{
*out = vips_image_new();
if( vips_image_pipeline_arrayv( *out,
VIPS_DEMAND_STYLE_THINSTRIP, in, NULL ) )
return( -1 );
(*out)->Bands /= 2;
(*out)->Xsize -= 2;
(*out)->Ysize -= 2;
if( vips_image_generate( *out,
vips_start_one, vips_canny_nonmax_generate, vips_stop_one,
in, NULL ) )
return( -1 );
return( 0 );
}
static int
vips_canny_build( VipsObject *object )
{
VipsCanny *canny = (VipsCanny *) object;
VipsImage **t = (VipsImage **) vips_object_local_array( object, 20 );
VipsImage *in;
VipsImage *Gx;
VipsImage *Gy;
if( VIPS_OBJECT_CLASS( vips_canny_parent_class )->build( object ) )
return( -1 );
in = canny->in;
if( vips_gaussblur( in, &t[0], canny->sigma, NULL ) )
return( -1 );
in = t[0];
/* Separated Sobel gives Gx / Gy. Aim for vector path.
*/
t[1] = vips_image_new_matrixv( 1, 3, 1.0, 2.0, 1.0 );
t[2] = vips_image_new_matrixv( 3, 1, 1.0, 0.0, -1.0 );
vips_image_set_double( t[2], "offset", 128.0 );
if( vips_conv( in, &t[3], t[1],
"precision", VIPS_PRECISION_INTEGER,
NULL ) ||
vips_conv( t[3], &t[4], t[2],
"precision", VIPS_PRECISION_INTEGER,
NULL ) )
return( -1 );
Gx = t[4];
t[5] = vips_image_new_matrixv( 3, 1, 1.0, 2.0, 1.0 );
t[6] = vips_image_new_matrixv( 1, 3, 1.0, 0.0, -1.0 );
vips_image_set_double( t[6], "offset", 128.0 );
if( vips_conv( in, &t[7], t[5],
"precision", VIPS_PRECISION_INTEGER,
NULL ) ||
vips_conv( t[7], &t[8], t[6],
"precision", VIPS_PRECISION_INTEGER,
NULL ) )
return( -1 );
Gy = t[8];
/* Form (G, theta), with theta coded.
*/
canny->args[0] = Gx;
canny->args[1] = Gy;
canny->args[2] = NULL;
if( vips_canny_polar( canny->args, &t[9] ) )
return( -1 );
in = t[9];
g_object_set( object, "out", vips_image_new(), NULL );
if( vips_image_write( in, canny->out ) )
return( -1 );
return( 0 );
}
static void
vips_canny_class_init( VipsCannyClass *class )
{
GObjectClass *gobject_class = G_OBJECT_CLASS( class );
VipsObjectClass *object_class = (VipsObjectClass *) class;
VipsOperationClass *operation_class = VIPS_OPERATION_CLASS( class );
gobject_class->set_property = vips_object_set_property;
gobject_class->get_property = vips_object_get_property;
object_class->nickname = "canny";
object_class->description = _( "gaussian blur" );
object_class->build = vips_canny_build;
operation_class->flags = VIPS_OPERATION_SEQUENTIAL;
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 );
}
static void
vips_canny_init( VipsCanny *canny )
{
canny->sigma = 1.4;
}
/**
* 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 );
}

2
libvips/convolution/convolution.c
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@ -168,6 +168,7 @@ vips_convolution_operation_init( void )
extern int vips_spcor_get_type( void );
extern int vips_sharpen_get_type( void );
extern int vips_gaussblur_get_type( void );
extern int vips_canny_get_type( void );
vips_conv_get_type();
vips_conva_get_type();
@ -180,4 +181,5 @@ vips_convolution_operation_init( void )
vips_spcor_get_type();
vips_sharpen_get_type();
vips_gaussblur_get_type();
vips_canny_get_type();
}

3
libvips/include/vips/convolution.h
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@ -70,6 +70,9 @@ int vips_spcor( VipsImage *in, VipsImage *ref, VipsImage **out, ... )
int vips_fastcor( VipsImage *in, VipsImage *ref, VipsImage **out, ... )
__attribute__((sentinel));
int vips_canny( VipsImage *in, VipsImage **out, ... )
__attribute__((sentinel));
#ifdef __cplusplus
}
#endif /*__cplusplus*/