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add "precision" control to canny

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This commit is contained in:
John Cupitt 2018-03-18 11:12:06 +00:00
parent 6d570ef0ff
commit c5bf128e39
1 changed files with 17 additions and 1 deletions
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18
libvips/convolution/canny.c
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@ -50,6 +50,7 @@ typedef struct _VipsCanny {
VipsImage *out;
double sigma;
VipsPrecision precision;
/* Need an image vector for start_many.
*/
@ -382,7 +383,9 @@ vips_canny_build( VipsObject *object )
in = canny->in;
if( vips_gaussblur( in, &t[0], canny->sigma, NULL ) )
if( vips_gaussblur( in, &t[0], canny->sigma,
"precision", canny->precision,
NULL ) )
return( -1 );
in = t[0];
@ -453,12 +456,20 @@ vips_canny_class_init( VipsCannyClass *class )
G_STRUCT_OFFSET( VipsCanny, sigma ),
0.01, 1000, 1.4 );
VIPS_ARG_ENUM( class, "precision", 103,
_( "Precision" ),
_( "Convolve with this precision" ),
VIPS_ARGUMENT_OPTIONAL_INPUT,
G_STRUCT_OFFSET( VipsCanny, precision ),
VIPS_TYPE_PRECISION, VIPS_PRECISION_FLOAT );
}
static void
vips_canny_init( VipsCanny *canny )
{
canny->sigma = 1.4;
canny->precision = VIPS_PRECISION_FLOAT;
}
/**
@ -471,6 +482,7 @@ vips_canny_init( VipsCanny *canny )
* Optional arguments:
*
* * @sigma: %gdouble, sigma for gaussian blur
* * @precision: #VipsPrecision, calculation accuracy
*
* Find edges by Canny's method: The maximum of the derivative of the gradient
* in the direction of the gradient. Output is float, except for uchar input,
@ -480,6 +492,10 @@ vips_canny_init( VipsCanny *canny )
* Use @sigma to control the scale over which gradient is measured. 1.4 is
* usually a good value.
*
* Use @precision to set the precision of edge detection. For uchar images,
* setting this to #VIPS_PRECISION_INTEGER will make edge detection much
* faster, but sacrifice some sensitivity.
*
* You will probably need to process the output further to eliminate weak
* edges.
*