Fix: convolute not defaulting to 0, 0 as starting point (#1228)

packages/plugin-color/src/index.js

@@ -583,7 +583,7 @@ export default () => ({
    * @param {number} w (optional) the width of the region to apply convolution to
    * @param {number} h (optional) the height of the region to apply convolution to
    * @param {function(Error, Jimp)} cb (optional) a callback for when complete
-   * @returns {Jimp }this for chaining of methods
+   * @returns {Jimp} this for chaining of methods
    */
   convolute(kernel, x, y, w, h, cb) {
     if (!Array.isArray(kernel))
@@ -613,10 +613,8 @@ export default () => ({
       }
     }
 
-    const ksize = (kernel.length - 1) / 2;
-
-    x = isDef(x) ? x : ksize;
-    y = isDef(y) ? y : ksize;
+    x = isDef(x) ? x : 0;
+    y = isDef(y) ? y : 0;
     w = isDef(w) ? w : this.bitmap.width - x;
     h = isDef(h) ? h : this.bitmap.height - y;
 

packages/plugin-color/test/convolution.test.js

@@ -57,6 +57,12 @@ describe("Convolution", function () {
     [0, 1, 1],
   ];
 
+  const blurM = [
+    [1 / 9, 1 / 9, 1 / 9],
+    [1 / 9, 1 / 9, 1 / 9],
+    [1 / 9, 1 / 9, 1 / 9],
+  ];
+
   it("3x3 sharp matrix on EDGE_EXTEND", (done) => {
     expectToBeJGD(
       imgMid.clone().convolution(sharpM).getJGDSync(),
@@ -150,6 +156,16 @@ describe("Convolution", function () {
     done();
   });
 
+  it("3x3 box blur matrix using convolute", async () => {
+    const expectedImg = await jimp.read(
+      getTestDir(__dirname) + "/images/tiles-blurred.png"
+    );
+
+    const image = await jimp.read(getTestDir(__dirname) + "/images/tiles.jpg");
+
+    expect(image.convolute(blurM).bitmap.data).toEqual(expectedImg.bitmap.data);
+  });
+
   it("new pixel value is greater than 255", async () => {
     const expectedImg = await jimp.read(
       getTestDir(__dirname) + "/images/qr-convoluted.png"