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Optimize Canny edge detector.
* Use separable convolution. * Merge thresholding and non-max suppression steps.
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@ -32,8 +32,8 @@ void imlib_edge_canny(image_t *src, rectangle_t *roi, int low_thresh, int high_t
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gvec_t *gm = fb_alloc0(src->w*src->h*sizeof*gm);
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//1. Noise Reduction with a 5x5 Gaussian filter
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imlib_morph(src, 2, kernel_gauss_5, 1.0f/159.0f, 0.0f);
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//1. Noise Reduction with a Gaussian filter
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imlib_sepconv3(src, kernel_gauss_3, 1.0f/16.0f, 0.0f);
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//2. Finding Image Gradients
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for (int y=roi->y+1; y<roi->y+roi->h-1; y++) {
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@ -77,14 +77,26 @@ void imlib_edge_canny(image_t *src, rectangle_t *roi, int low_thresh, int high_t
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}
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// 3. Hysteresis Thresholding
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for (int y=roi->y+1; y<roi->y+roi->h-1; y++) {
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for (int x=roi->x+1; x<roi->x+roi->w-1; x++) {
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gvec_t *vc = &gm[y*w+x];
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if (vc->g >= high_thresh) {
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vc->g = vc->g;
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} else if (vc->g < low_thresh) {
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vc->g = 0;
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} else if (gm[(y-1)*w+(x-1)].g >= high_thresh ||
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// 4. Non-maximum Suppression and output
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for (int y=roi->y; y<roi->y+roi->h; y++) {
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for (int x=roi->x; x<roi->x+roi->w; x++) {
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int i = y*w+x;
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gvec_t *va=NULL, *vb=NULL, *vc = &gm[i];
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// Clear the borders
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if (y == (roi->y) || y == (roi->y+roi->h-1) ||
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x == (roi->x) || x == (roi->x+roi->w-1)) {
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src->data[i] = 0;
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continue;
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}
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if (vc->g < low_thresh) {
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// Not an edge
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src->data[i] = 0;
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continue;
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// Check if strong or weak edge
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} else if (vc->g >= high_thresh ||
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gm[(y-1)*w+(x-1)].g >= high_thresh ||
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gm[(y-1)*w+(x+0)].g >= high_thresh ||
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gm[(y-1)*w+(x+1)].g >= high_thresh ||
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gm[(y+0)*w+(x-1)].g >= high_thresh ||
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@ -93,20 +105,7 @@ void imlib_edge_canny(image_t *src, rectangle_t *roi, int low_thresh, int high_t
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gm[(y+1)*w+(x+0)].g >= high_thresh ||
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gm[(y+1)*w+(x+1)].g >= high_thresh) {
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vc->g = vc->g;
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} else {
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vc->g = 0;
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}
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}
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}
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// 4. Non-maximum Suppression and output
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for (int y=roi->y; y<roi->y+roi->h; y++) {
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for (int x=roi->x; x<roi->x+roi->w; x++) {
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int i = y*w+x;
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gvec_t *va=NULL, *vb=NULL, *vc = &gm[i];
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if (y < (roi->y+2) || y > (roi->y+roi->h-3) ||
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x < (roi->x+2) || x > (roi->x+roi->w-3)) {
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} else { // Not an edge
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src->data[i] = 0;
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continue;
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}
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