try interpolating theta
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John Cupitt
parent
ce6d37189c
commit
43cbd32955
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@ -88,13 +88,13 @@ vips_canny_polar_generate( VipsRegion *or,
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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 = 360 + VIPS_DEG( atan2( x, y ) );
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int a = VIPS_DEG( atan2( x, y ) ) + 360;
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/* Faster than hypot() for int args. Scale down
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* or we'll clip on very hard edges.
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*/
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q[0] = 0.5 * sqrt( x * x + y * y );
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q[1] = ((a + 22) / 45) & 0x3;
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q[1] = 256 * a / 360;
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q += 2;
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}
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@ -111,13 +111,8 @@ vips_canny_polar_generate( VipsRegion *or,
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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:
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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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* 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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@ -163,6 +158,12 @@ vips_canny_nonmax_generate( VipsRegion *or,
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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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@ -183,8 +184,9 @@ vips_canny_nonmax_generate( VipsRegion *or,
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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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VipsPel low = p[offseta[theta]];
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VipsPel high = p[offsetb[theta]];
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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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@ -230,6 +232,111 @@ vips_canny_nonmax( VipsImage *in, VipsImage **out )
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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_build( VipsObject *object )
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{
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@ -292,7 +399,8 @@ vips_canny_build( VipsObject *object )
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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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vips_canny_nonmax( t[10], &t[11] ) )
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//vips_canny_nonmax( t[10], &t[11] ) )
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vips_canny_nonmaxi( t[10], &t[11] ) )
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return( -1 );
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in = t[11];
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@ -344,7 +452,7 @@ vips_canny_class_init( VipsCannyClass *class )
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static void
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vips_canny_init( VipsCanny *canny )
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{
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canny->sigma = 1.4;
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canny->sigma = 1.5;
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}
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/**
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