mirror of
https://github.com/openseadragon/openseadragon.git
synced 2024-11-29 08:36:10 +03:00
72 lines
1.7 KiB
GLSL
72 lines
1.7 KiB
GLSL
precision mediump float;
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uniform sampler2D u_tile;
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uniform vec2 u_tile_size;
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varying vec2 v_tile_pos;
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// Sum a vector
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float sum3(vec3 v) {
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return dot(v,vec3(1));
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}
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// Weight of a matrix
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float weigh3(mat3 m) {
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return sum3(m[0])+sum3(m[1])+sum3(m[2]);
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}
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// Take the outer product
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mat3 outer3(vec3 c, vec3 r) {
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mat3 goal;
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for (int i =0; i<3; i++) {
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goal[i] = r*c[i];
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}
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return goal;
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}
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//*~*~*~*~*~*~*~*~*~*~*~*~*~
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// Now for the Sobel Program
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//*~
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// Sample the color at offset
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vec3 color(float dx, float dy) {
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// calculate the color of sampler at an offset from position
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return texture2D(u_tile, v_tile_pos+vec2(dx,dy)).rgb;
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}
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float sobel(mat3 kernel, vec3 near_in[9]) {
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// nearest pixels
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mat3 near_out[3];
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// Get all near_in pixels
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for (int i = 0; i < 3; i++) {
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near_out[i][0] = kernel[0]*vec3(near_in[0][i],near_in[1][i],near_in[2][i]);
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near_out[i][1] = kernel[1]*vec3(near_in[3][i],near_in[4][i],near_in[5][i]);
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near_out[i][2] = kernel[2]*vec3(near_in[6][i],near_in[7][i],near_in[8][i]);
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}
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// convolve the kernel with the nearest pixels
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return length(vec3(weigh3(near_out[0]),weigh3(near_out[1]),weigh3(near_out[2])));
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}
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void main() {
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// Prep work
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vec3 near_in[9];
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vec3 mean = vec3(1,2,1);
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vec3 slope = vec3(-1,0,1);
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mat3 sobelX = outer3(mean,slope);
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mat3 sobelY = outer3(slope,mean);
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vec2 u = vec2(1./u_tile_size.x, 1./u_tile_size.y);
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// Calculate coordinates of nearest points
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for (int i = 0; i < 9; i++) {
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near_in[i] = color(mod(float(i),3.)*u.x, float(i/3-1)*u.y);
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}
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// Show the mixed XY contrast
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float edgeX = sobel(sobelX, near_in);
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float edgeY = sobel(sobelY, near_in);
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float mixed = length(vec2(edgeX,edgeY));
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// mixed = (max(mixed,0.5)-0.5);
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gl_FragColor = vec4(vec3(mixed),1);
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}
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