From c889f65ac0fbb7cfc5dc35f08bccc607028da91d Mon Sep 17 00:00:00 2001
From: Mike Bostock <mbostock@gmail.com>
Date: Fri, 1 Jul 2022 20:22:47 -0400
Subject: [PATCH] blurImage

---
 src/blur.js  | 40 ++++++++++++++++++++++++++++++----------
 src/index.js |  2 +-
 2 files changed, 31 insertions(+), 11 deletions(-)

diff --git a/src/blur.js b/src/blur.js
index 9879c1a..49bc795 100644
--- a/src/blur.js
+++ b/src/blur.js
@@ -1,10 +1,9 @@
 export function blur1(values, r) {
   if (!((r = +r) >= 0)) throw new RangeError("invalid r");
-  const length = Math.floor(values.length);
-  if (!(length >= 0)) throw new RangeError("invalid length");
+  const length = values.length;
   if (!length || !r) return values;
-  const temp = values.slice();
   const blur = blurf(r);
+  const temp = values.slice();
   blur(values, temp, 0, length, 1);
   blur(temp, values, 0, length, 1);
   blur(values, temp, 0, length, 1);
@@ -17,27 +16,37 @@ export function blur2(data, rx, ry = rx) {
   let {data: values, width, height} = data;
   if (!((width = Math.floor(width)) >= 0)) throw new RangeError("invalid width");
   if (!((height = Math.floor(height)) >= 0)) throw new RangeError("invalid height");
-  if (!width || !height || (!rx && !ry)) return data;
+  blur2d(values, width, height, rx && blurf(rx), ry && blurf(ry));
+  return data;
+}
+
+export function blurImage(data, rx, ry = rx) {
+  if (!((rx = +rx) >= 0)) throw new RangeError("invalid rx");
+  if (!((ry = +ry) >= 0)) throw new RangeError("invalid ry");
+  const {data: values, width, height} = data;
+  blur2d(values, width, height, rx && blurfImage(rx), ry && blurfImage(ry));
+  return data;
+}
+
+function blur2d(values, width, height, blurx, blury) {
+  if (!width || !height || (!blurx && !blury)) return;
   const temp = values.slice();
-  const blurx = blurf(rx);
-  const blury = blurf(ry);
-  if (rx && ry) {
+  if (blurx && blury) {
     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);
-  } else if (rx) {
+  } else if (blurx) {
     blurh(blurx, values, temp, width, height);
     blurh(blurx, temp, values, width, height);
     blurh(blurx, values, temp, width, height);
-  } else if (ry) {
+  } else if (blury) {
     blurv(blury, values, temp, width, height);
     blurv(blury, temp, values, width, height);
     blurv(blury, values, temp, width, height);
   }
-  return data;
 }
 
 function blurh(blur, T, S, w, h) {
@@ -52,6 +61,17 @@ function blurv(blur, T, S, w, h) {
   }
 }
 
+function blurfImage(radius) {
+  const blur = blurf(radius);
+  return (T, S, start, stop, step) => {
+    start <<= 2, stop <<= 2, step <<= 2;
+    blur(T, S, start + 0, stop + 0, step);
+    blur(T, S, start + 1, stop + 1, step);
+    blur(T, S, start + 2, stop + 2, step);
+    blur(T, S, start + 3, stop + 3, step);
+  };
+}
+
 // Given a target array T, a source array S, sets each value T[i] to the average
 // of {S[i - r], …, S[i], …, S[i + r]}, where r = ⌊radius⌋, start <= i < stop,
 // for each i, i + step, i + 2 * step, etc., and where S[j] is clamped between
diff --git a/src/index.js b/src/index.js
index 11b1b5e..74a901e 100644
--- a/src/index.js
+++ b/src/index.js
@@ -1,7 +1,7 @@
 export {default as bisect, bisectRight, bisectLeft, bisectCenter} from "./bisect.js";
 export {default as ascending} from "./ascending.js";
 export {default as bisector} from "./bisector.js";
-export {blur1, blur2} from "./blur.js";
+export {blur1, blur2, blurImage} from "./blur.js";
 export {default as count} from "./count.js";
 export {default as cross} from "./cross.js";
 export {default as cumsum} from "./cumsum.js";