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improve smartcrop 

add a gaussblur before maxpos ... this represents the size of the crop
area, or how large an area we should consider when calculating the best
position

see https://github.com/jcupitt/libvips/issues/619
This commit is contained in:
John Cupitt 2017-03-16 13:52:09 +00:00
parent 18586bec8a
commit c00c518228
1 changed files with 10 additions and 5 deletions
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15
libvips/conversion/smartcrop.c
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@ -218,17 +218,22 @@ vips_smartcrop_attention( VipsSmartcrop *smartcrop,
vips_more_const1( t[14], &t[15], 60.0, NULL ) ) vips_more_const1( t[14], &t[15], 60.0, NULL ) )
return( -1 ); return( -1 );
/* Sum, shrink and find maxpos. We could blur too, but the box filter /* Sum, shrink, blur and find maxpos.
* shrink uses will do more or less the same thing. Shrink to ~ 32x32, it *
* should give us enough precision for positioning, while also grouping * The size we shrink to gives the precision with which we can place
* high-value areas. * the crop, the amount of blur is related to the size of the crop
* area: how large an area we want to consider for the scoring
* function.
*
* We should probably vary these numbers with the image and crop size.
*/ */
hshrink = ceil( in->Xsize / 32.0 ); hshrink = ceil( in->Xsize / 32.0 );
vshrink = ceil( in->Ysize / 32.0 ); vshrink = ceil( in->Ysize / 32.0 );
if( vips_add( t[7], t[19], &t[16], NULL ) || if( vips_add( t[7], t[19], &t[16], NULL ) ||
vips_add( t[16], t[15], &t[17], NULL ) || vips_add( t[16], t[15], &t[17], NULL ) ||
vips_shrink( t[17], &t[20], hshrink, vshrink, NULL ) || vips_shrink( t[17], &t[20], hshrink, vshrink, NULL ) ||
vips_max( t[20], &max, "x", &x_pos, "y", &y_pos, NULL ) ) vips_gaussblur( t[20], &t[21], 10.0, NULL ) ||
vips_max( t[21], &max, "x", &x_pos, "y", &y_pos, NULL ) )
return( -1 ); return( -1 );
/* Centre the crop over the max. /* Centre the crop over the max.