perf: optimize bilinear (#296)

close: #313

Author: lpatiny

scripts/benchmark/large.jpg

@@ -0,0 +1,15 @@
+// run with `ts-node-transpile-only scripts/benchmark/resize.benchmark.ts`
+
+import { read } from '../../src';
+import { join } from 'path';
+
+async function doAll() {
+  const image = await read(join(__dirname, 'large.jpg'));
+
+  console.time('resize');
+
+  image.resize({ width: 6000, height: 4000, interpolationType: 'bilinear' });
+  console.timeEnd('resize');
+}
+
+doAll();

scripts/benchmark/resize.benchmark.ts

@@ -90,21 +90,28 @@ function interpolateBilinear(
   const px0 = Math.floor(column);
   const py0 = Math.floor(row);
 
-  if (px0 === column && py0 === row) {
-    return interpolateBorder(px0, py0, channel, image);
-  }
-
   const px1 = px0 + 1;
   const py1 = py0 + 1;
 
-  const vx0y0 = interpolateBorder(px0, py0, channel, image);
-  const vx1y0 = interpolateBorder(px1, py0, channel, image);
-  const vx0y1 = interpolateBorder(px0, py1, channel, image);
-  const vx1y1 = interpolateBorder(px1, py1, channel, image);
-
-  const r1 = (px1 - column) * vx0y0 + (column - px0) * vx1y0;
-  const r2 = (px1 - column) * vx0y1 + (column - px0) * vx1y1;
-  return round((py1 - row) * r1 + (row - py0) * r2);
+  if (px1 < image.width && py1 < image.height && px0 >= 0 && py0 >= 0) {
+    const vx0y0 = image.getValue(px0, py0, channel);
+    const vx1y0 = image.getValue(px1, py0, channel);
+    const vx0y1 = image.getValue(px0, py1, channel);
+    const vx1y1 = image.getValue(px1, py1, channel);
+
+    const r1 = (px1 - column) * vx0y0 + (column - px0) * vx1y0;
+    const r2 = (px1 - column) * vx0y1 + (column - px0) * vx1y1;
+    return round((py1 - row) * r1 + (row - py0) * r2);
+  } else {
+    const vx0y0 = interpolateBorder(px0, py0, channel, image);
+    const vx1y0 = interpolateBorder(px1, py0, channel, image);
+    const vx0y1 = interpolateBorder(px0, py1, channel, image);
+    const vx1y1 = interpolateBorder(px1, py1, channel, image);
+
+    const r1 = (px1 - column) * vx0y0 + (column - px0) * vx1y0;
+    const r2 = (px1 - column) * vx0y1 + (column - px0) * vx1y1;
+    return round((py1 - row) * r1 + (row - py0) * r2);
+  }
 }
 
 /**

src/utils/interpolatePixel.ts

@@ -5,8 +5,13 @@
  * @returns The rounded value.
  */
 export function round(value: number): number {
-  if (value % 0.5 !== 0) {
-    return Math.round(value);
+  const integer = Math.trunc(value);
+  const decimal = value - integer;
+  if (decimal < 0.5) {
+    return integer;
+  } else if (decimal > 0.5) {
+    return integer + 1;
+  } else {
+    return integer % 2 === 0 ? integer : integer + 1;
   }
-  return Math.floor(value) % 2 === 0 ? Math.floor(value) : Math.ceil(value);
 }