feat: add a sum operation (#384)

Author: EscapedGibbon

src/Image.ts

@@ -1,7 +1,7 @@
 import { RgbColor } from 'colord';
 
 import { Mask } from './Mask';
-import { subtract, SubtractImageOptions } from './compare';
+import { subtract, add, SubtractImageOptions } from './compare';
 import { median } from './compute/median';
 import { variance } from './compute/variance';
 import { correctColor } from './correctColor';
@@ -636,6 +636,10 @@ export class Image {
     return subtract(this, other, options);
   }
 
+  public add(other: Image): Image {
+    return add(this, other);
+  }
+
   // COMPUTE
 
   public histogram(options?: HistogramOptions): Uint32Array {

src/compare/__tests__/add.test.ts

@@ -0,0 +1,65 @@
+import { add } from '../add';
+
+test('add image to itself', () => {
+  const image = testUtils.createRgbImage([[5, 5, 5, 10, 10, 10, 15, 15, 15]]);
+  const other = image;
+  expect(add(image, other)).toMatchImageData([
+    [10, 10, 10, 20, 20, 20, 30, 30, 30],
+  ]);
+});
+
+test('add two different images', () => {
+  const image = testUtils.createRgbImage([[5, 5, 5, 10, 10, 10, 15, 15, 15]]);
+  const other = testUtils.createRgbImage([[0, 0, 0, 20, 20, 20, 15, 15, 15]]);
+  expect(add(image, other)).toMatchImageData([
+    [5, 5, 5, 30, 30, 30, 30, 30, 30],
+  ]);
+});
+
+test('add two different images whose sum exceeds the maxValue', () => {
+  const image = testUtils.createRgbImage([
+    [200, 200, 5, 10, 10, 10, 15, 15, 15],
+  ]);
+  const other = testUtils.createRgbImage([
+    [240, 200, 20, 20, 250, 20, 15, 15, 15],
+  ]);
+  expect(image.add(other)).toMatchImageData([
+    [255, 255, 25, 30, 255, 30, 30, 30, 30],
+  ]);
+});
+
+test('different bitDepth should throw', () => {
+  const image = testUtils.createRgbImage([[5, 5, 5, 10, 10, 10, 15, 15, 15]], {
+    bitDepth: 16,
+  });
+  const other = testUtils.createRgbImage([[0, 0, 0, 20, 20, 20, 15, 15, 15]], {
+    bitDepth: 8,
+  });
+  expect(() => {
+    return add(image, other);
+  }).toThrow('both images must have the same alpha and bitDepth');
+});
+
+test('different size images should throw', () => {
+  const image = testUtils.createRgbImage([[5, 5, 5, 10, 10, 10, 15, 15, 15]]);
+  const other = testUtils.createRgbImage([[5, 5, 5, 10, 10, 10]]);
+  expect(() => {
+    add(image, other);
+  }).toThrow(`both images must have the same size`);
+});
+
+test('different number of channels should throw', () => {
+  const image = testUtils.createGreyImage([[5, 10, 15]]);
+  const other = testUtils.createRgbImage([[1, 1, 1, 5, 5, 5, 10, 10, 10]]);
+  expect(() => {
+    image.subtract(other);
+  }).toThrow(`both images must have the same number of channels`);
+});
+
+test('different number of channels should throw', () => {
+  const image = testUtils.createGreyImage([[5, 10, 15]]);
+  const other = testUtils.createRgbImage([[1, 1, 1, 5, 5, 5, 10, 10, 10]]);
+  expect(() => {
+    image.subtract(other);
+  }).toThrow(`both images must have the same number of channels`);
+});

src/compare/add.ts

@@ -0,0 +1,34 @@
+import { Image } from '..';
+import { getClamp } from '../utils/clamp';
+import checkProcessable from '../utils/validators/checkProcessable';
+import { validateForComparison } from '../utils/validators/validators';
+/**
+ *
+ * Calculate a new image that is the sum between the current image and the otherImage.
+ * @param image - Image to which to add.
+ * @param otherImage - Image to add.
+ * @returns The summed image.
+ */
+export function add(image: Image, otherImage: Image): Image {
+  if (image instanceof Image) {
+    checkProcessable(image, {
+      bitDepth: [8, 16],
+      components: [1, 3],
+      alpha: false,
+    });
+  }
+
+  validateForComparison(image, otherImage);
+
+  const newImage = image.clone();
+  const clamp = getClamp(image);
+  for (let index = 0; index < image.size; index++) {
+    for (let channel = 0; channel < image.channels; channel++) {
+      const value =
+        image.getValueByIndex(index, channel) +
+        otherImage.getValueByIndex(index, channel);
+      newImage.setValueByIndex(index, channel, clamp(value));
+    }
+  }
+  return newImage;
+}

src/compare/index.ts

@@ -3,3 +3,4 @@ export * from './computePsnr';
 export * from './computeRmse';
 export * from './computeSsim';
 export * from './subtract';
+export * from './add';