fix: resize nearest

chirurgical fix, rework of #453

Refs: https://github.com/image-js/image-js-typescript/issues/452

Author: tpoisseau

src/geometry/__tests__/resize.test.ts

@@ -1,25 +1,43 @@
-import { encodePng } from '../../save';
+import path from 'node:path';
 
-test.skip('compare result of resize with opencv (nearest)', () => {
+import { encodePng, write } from '../../save';
+
+test('compare result of resize with opencv (nearest)', async () => {
   const img = testUtils.load('opencv/test.png');
+  const expectedImg = testUtils.load('opencv/testResizeNearest.png');
 
   const resized = img.resize({
     xFactor: 10,
     yFactor: 10,
     interpolationType: 'nearest',
   });
 
+  const substraction = expectedImg.clone().subtract(resized);
+  await write(
+    path.join(__dirname, 'resize_nearest_substraction.png'),
+    substraction,
+  );
+  await write(path.join(__dirname, 'resize_nearest.png'), resized);
+
   expect(resized).toMatchImage('opencv/testResizeNearest.png');
 });
 
-test.skip('compare result of resize with opencv (bilinear)', () => {
+test.skip('compare result of resize with opencv (bilinear)', async () => {
   const img = testUtils.load('opencv/test.png');
+  const expectedImg = testUtils.load('opencv/testResizeBilinear.png');
 
   const resized = img.resize({
     xFactor: 10,
     yFactor: 10,
   });
 
+  const substraction = expectedImg.clone().subtract(resized);
+  await write(
+    path.join(__dirname, 'resize_bilinear_substraction.png'),
+    substraction,
+  );
+  await write(path.join(__dirname, 'resize_bilinear.png'), resized);
+
   expect(resized).toMatchImage('opencv/testResizeBilinear.png');
 });
 

src/geometry/resize.ts

@@ -1,12 +1,14 @@
 import { Image } from '../Image';
 import { getClamp } from '../utils/clamp';
-import { getBorderInterpolation, BorderType } from '../utils/interpolateBorder';
+import { BorderType, getBorderInterpolation } from '../utils/interpolateBorder';
 import {
   getInterpolationFunction,
   InterpolationType,
 } from '../utils/interpolatePixel';
 import { assert } from '../utils/validators/assert';
 
+import { transform } from './transform';
+
 export interface ResizeOptions {
   /**
    * Width of the output image.
@@ -58,7 +60,25 @@ export function resize(image: Image, options: ResizeOptions): Image {
     borderType = 'constant',
     borderValue = 0,
   } = options;
-  const { width, height } = checkOptions(image, options);
+  const { width, height, xFactor, yFactor } = checkOptions(image, options);
+
+  if (interpolationType === 'nearest') {
+    return transform(
+      image,
+      [
+        [xFactor, 0, xFactor / 2],
+        [0, yFactor, yFactor / 2],
+      ],
+      {
+        interpolationType,
+        borderType,
+        borderValue,
+        height,
+        width,
+      },
+    );
+  }
+
   const newImage = Image.createFrom(image, { width, height });
   const interpolate = getInterpolationFunction(interpolationType);
   const interpolateBorder = getBorderInterpolation(borderType, borderValue);