Blit src params Issue

packages/plugin-blit/src/index.js

@@ -55,18 +55,21 @@ export default () => ({
     srcw = Math.round(srcw);
     srch = Math.round(srch);
 
-    const maxw = this.bitmap.width;
-    const maxh = this.bitmap.height;
+    const maxWidth = this.bitmap.width;
+    const maxHeight = this.bitmap.height;
     const baseImage = this;
 
     src.scanQuiet(srcx, srcy, srcw, srch, function(sx, sy, idx) {
+      const xOffset = x + sx - srcx;
+      const yOffset = y + sy - srcy;
+
       if (
-        x + sx >= 0 &&
-        y + sy >= 0 &&
-        maxw - x - sx > 0 &&
-        maxh - y - sy > 0
+        xOffset >= 0 &&
+        yOffset >= 0 &&
+        maxWidth - xOffset > 0 &&
+        maxHeight - yOffset > 0
       ) {
-        const dstIdx = baseImage.getPixelIndex(x + sx - srcx, y + sy - srcy);
+        const dstIdx = baseImage.getPixelIndex(xOffset, yOffset);
         const src = {
           r: this.bitmap.data[idx],
           g: this.bitmap.data[idx + 1],

packages/plugin-blit/test/blit.test.js

@@ -5,6 +5,7 @@ import configure from '@jimp/custom';
 import blit from '../src';
 
 const jimp = configure({ types: [jpeg], plugins: [blit] }, Jimp);
+const testDir = getTestDir(__dirname);
 
 describe('Blit over image', function() {
   this.timeout(15000);
@@ -157,14 +158,77 @@ describe('Blit over image', function() {
   });
 
   it('blit alpha', async () => {
-    const expectedImg = await Jimp.read(
-      getTestDir(__dirname) + '/images/blit-alpha.png'
-    );
-    const dice = await Jimp.read(getTestDir(__dirname) + '/images/dice.png');
-    const image = await Jimp.read(getTestDir(__dirname) + '/images/cops.jpg');
+    const expectedImg = await Jimp.read(testDir + '/images/blit-alpha.png');
+    const dice = await Jimp.read(testDir + '/images/dice.png');
+    const image = await Jimp.read(testDir + '/images/cops.jpg');
 
     image
       .blit(dice, 0, 0)
       .bitmap.data.should.be.deepEqual(expectedImg.bitmap.data);
   });
+
+  async function createCat(catNum, len) {
+    let imgHeight = 60;
+
+    const butt = await Jimp.read(testDir + '/images/cat_butt.png');
+    const head = await Jimp.read(testDir + '/images/cat_head.png');
+    const fuzz = await Jimp.read(testDir + '/images/cat_fuzz.png');
+
+    let longCat = len;
+    longCat = longCat > 20 ? 20 : longCat;
+    longCat = longCat <= 1 ? 1 : longCat;
+
+    const cat =
+      Math.floor(catNum * (head.bitmap.height / imgHeight)) * imgHeight;
+
+    const newImage = await Jimp.create(
+      butt.bitmap.width + head.bitmap.width + fuzz.bitmap.width * longCat,
+      imgHeight,
+      0x00000000
+    );
+
+    newImage.blit(butt, 0, 0, 0, cat, butt.bitmap.width, imgHeight);
+    for (let i = 0; i < longCat; i++) {
+      newImage.blit(
+        fuzz,
+        butt.bitmap.width + fuzz.bitmap.width * i,
+        0,
+        0,
+        cat,
+        fuzz.bitmap.width,
+        imgHeight
+      );
+    }
+    newImage.blit(
+      head,
+      butt.bitmap.width + fuzz.bitmap.width * longCat,
+      0,
+      0,
+      cat,
+      head.bitmap.width,
+      imgHeight
+    );
+
+    return newImage;
+  }
+
+  it('uses src params correctly', async () => {
+    const expectedSmall = await Jimp.read(
+      testDir + '/images/cat-results/small-cat.png'
+    );
+    const small = await createCat(0.3, 1);
+    small.bitmap.data.should.be.deepEqual(expectedSmall.bitmap.data);
+
+    const expectedMedium = await Jimp.read(
+      testDir + '/images/cat-results/medium-cat.png'
+    );
+    const medium = await createCat(0.6, 7);
+    medium.bitmap.data.should.be.deepEqual(expectedMedium.bitmap.data);
+
+    const expectedLarge = await Jimp.read(
+      testDir + '/images/cat-results/large-cat.png'
+    );
+    const large = await createCat(0.9, 20);
+    large.bitmap.data.should.be.deepEqual(expectedLarge.bitmap.data);
+  });
 });