51 lines
1.4 KiB
JavaScript
51 lines
1.4 KiB
JavaScript
import ImageRegion from './ImageRegion.mjs';
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export function makeGaussianKernel(size) {
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const sz = Math.ceil(size * 3);
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const kernel = new Float32Array(sz * 2 + 1);
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const norm = 1 / (size * Math.sqrt(Math.PI * 2));
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const expNorm = -0.5 / (size * size);
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for(let i = -sz; i <= sz; ++ i) {
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kernel[i + sz] = Math.exp(i * i * expNorm) * norm;
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}
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return {kernel, sz};
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}
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export function blur1D(region, size, {target = null} = {}) {
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const tgt = region.checkOrMakeTarget(target);
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const {width, height, stepX, stepY, dim} = region;
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const {kernel, sz} = makeGaussianKernel(size);
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for(let x = 0; x < width; ++ x) {
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const i0 = -Math.min(sz, x);
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const i1 = Math.min(sz, width - x);
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for(let d = 0; d < dim; ++ d) {
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const psx = region.indexOf(x, 0, d);
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const ptx = tgt.indexOf(x, 0, d);
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for(let y = 0; y < height; ++ y) {
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const ps = psx + y * stepY;
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let accum = 0;
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for(let i = i0; i < i1; ++ i) {
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accum += region.values[ps + i * stepX] * kernel[i + sz];
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}
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tgt.values[ptx + y * tgt.stepY] = accum;
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}
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}
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}
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return tgt;
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}
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export function blur2D(region, size, {target = null, temp = null} = {}) {
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const tgt = region.checkOrMakeTarget(target);
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const tmp = blur1D(region, size, {target: temp});
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blur1D(tmp.transposed(), size, {target: tgt.transposed()});
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return tgt;
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}
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ImageRegion.prototype.blur = function(size, options) {
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return blur2D(this, size, options);
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};
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