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blur2 with stride #254

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blur2 with stride #254

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37 changes: 20 additions & 17 deletions src/blur.js
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Original file line number Diff line number Diff line change
Expand Up @@ -11,37 +11,40 @@ export function blur1(values, r) {
return values;
}

export function blur2(values, width, rx, ry = rx) {
export function blur2(values, width, rx, ry = rx, stride = 1) {
if (!((rx = +rx) >= 0)) throw new RangeError("invalid rx");
if (!((ry = +ry) >= 0)) throw new RangeError("invalid ry");
if (!((width = Math.floor(width)) >= 0)) throw new RangeError("invalid width");
if (!((stride = Math.floor(stride)) > 0)) throw new RangeError("invalid stride");
if (!width || (!rx && !ry)) return values;
const temp = values.slice();
const height = Math.floor(values.length / width);
const height = Math.floor(values.length / width / stride);
const blurx = blurf(rx);
const blury = blurf(ry);
if (rx && ry) {
blurh(blurx, temp, values, width, height);
blurh(blurx, values, temp, width, height);
blurh(blurx, temp, values, width, height);
blurv(blury, values, temp, width, height);
blurv(blury, temp, values, width, height);
blurv(blury, values, temp, width, height);
blurh(blurx, temp, values, width, height, stride);
blurh(blurx, values, temp, width, height, stride);
blurh(blurx, temp, values, width, height, stride);
blurv(blury, values, temp, width * stride, height);
blurv(blury, temp, values, width * stride, height);
blurv(blury, values, temp, width * stride, height);
} else if (rx) {
blurh(blurx, values, temp, width, height);
blurh(blurx, temp, values, width, height);
blurh(blurx, values, temp, width, height);
blurh(blurx, values, temp, width, height, stride);
blurh(blurx, temp, values, width, height, stride);
blurh(blurx, values, temp, width, height, stride);
} else if (ry) {
blurv(blury, values, temp, width, height);
blurv(blury, temp, values, width, height);
blurv(blury, values, temp, width, height);
blurv(blury, values, temp, width * stride, height);
blurv(blury, temp, values, width * stride, height);
blurv(blury, values, temp, width * stride, height);
}
return values;
}

function blurh(blur, T, S, w, h) {
for (let y = 0, n = w * h; y < n;) {
blur(T, S, y, y += w, 1);
function blurh(blur, T, S, w, h, stride = 1) {
for (let a = 0; a < stride; ++a) {
for (let y = a, n = w * h * stride; y < n;) {
blur(T, S, y, y += w * stride, stride);
}
}
}

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37 changes: 37 additions & 0 deletions test/blur-test.js
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Original file line number Diff line number Diff line change
Expand Up @@ -206,3 +206,40 @@ it("blur2(values, width, 0, ry) does vertical blurring", () => {
function round(x) {
return Math.round(x * 1000) / 1000 || 0;
}

// a stride on blur1 is the same as using a vertical blur2 with width=stride
it("blur1 & stride", () => {
const values = [-27,270,-2700,27000, 0,0,0,0];
assert.deepStrictEqual(blur2(values, 4, 0, 1), [-14,140,-1400,14000, -13,130,-1300,13000]);
});

it("blur2 & stride", () => {
assert.deepStrictEqual(blur2([
729,0,0,0, 0,0,0,0,
0,0,0,0, 0,0,0,0
], 2, 1, 1, 4), [
196,0,0,0, 182,0,0,0,
182,0,0,0, 169,0,0,0
]);
assert.deepStrictEqual(blur2([
0,729,0,0, 0,0,0,0,
0,0,0,0, 0,0,0,0
], 2, 1, 1, 4), [
0,196,0,0, 0,182,0,0,
0,182,0,0, 0,169,0,0
]);
assert.deepStrictEqual(blur2([
0,0,729,0, 0,0,0,0,
0,0,0,0, 0,0,0,0
], 2, 1, 1, 4), [
0,0,196,0, 0,0,182,0,
0,0,182,0, 0,0,169,0
]);
assert.deepStrictEqual(blur2([
0,0,0,729, 0,0,0,0,
0,0,0,0, 0,0,0,0
], 2, 1, 1, 4), [
0,0,0,196, 0,0,0,182,
0,0,0,182, 0,0,0,169
]);
});