Adding a Seam Carving algorithm with Dynamic Programming implementation. (trekhleb#693)

* Adding a Seam Carving algorithm with Dynamic Programming implementation.

* Adding a Seam Carving algorithm with Dynamic Programming implementation.

* Adding a Seam Carving algorithm with Dynamic Programming implementation.

* Testing Husky integration.

* Testing Husky integration.

Author: trekhleb

.husky/.gitignore

@@ -0,0 +1 @@
+_

.husky/pre-commit

@@ -0,0 +1,5 @@
+#!/bin/sh
+. "$(dirname "$0")/_/husky.sh"
+
+# npm run lint
+# npm run test

.huskyrc.json

@@ -152,6 +152,8 @@ a set of rules that precisely define a sequence of operations.
   * `B` [NanoNeuron](https://github.com/trekhleb/nano-neuron) - 7 simple JS functions that illustrate how machines can actually learn (forward/backward propagation)
   * `B` [k-NN](src/algorithms/ml/knn) - k-nearest neighbors classification algorithm
   * `B` [k-Means](src/algorithms/ml/k-means) - k-Means clustering algorithm
+* **Image Processing**
+  * `B` [Seam Carving](src/algorithms/image-processing/seam-carving) - content-aware image resizing algorithm
 * **Uncategorized**
   * `B` [Tower of Hanoi](src/algorithms/uncategorized/hanoi-tower)
   * `B` [Square Matrix Rotation](src/algorithms/uncategorized/square-matrix-rotation) - in-place algorithm
@@ -203,6 +205,7 @@ algorithm is an abstraction higher than a computer program.
   * `B` [Unique Paths](src/algorithms/uncategorized/unique-paths)
   * `B` [Rain Terraces](src/algorithms/uncategorized/rain-terraces) - trapping rain water problem
   * `B` [Recursive Staircase](src/algorithms/uncategorized/recursive-staircase) - count the number of ways to reach to the top
+  * `B` [Seam Carving](src/algorithms/image-processing/seam-carving) - content-aware image resizing algorithm
   * `A` [Levenshtein Distance](src/algorithms/string/levenshtein-distance) - minimum edit distance between two sequences
   * `A` [Longest Common Subsequence](src/algorithms/sets/longest-common-subsequence) (LCS)
   * `A` [Longest Common Substring](src/algorithms/string/longest-common-substring)

README.md

@@ -7,7 +7,8 @@
     "lint": "eslint ./src/**",
     "test": "jest",
     "coverage": "npm run test -- --coverage",
-    "ci": "npm run lint && npm run coverage"
+    "ci": "npm run lint && npm run coverage",
+    "prepare": "husky install"
   },
   "repository": {
     "type": "git",
@@ -37,13 +38,14 @@
     "@babel/cli": "7.12.10",
     "@babel/preset-env": "7.12.11",
     "@types/jest": "26.0.19",
+    "canvas": "^2.7.0",
     "eslint": "7.16.0",
     "eslint-config-airbnb": "18.2.1",
     "eslint-plugin-import": "2.22.1",
     "eslint-plugin-jest": "24.1.3",
     "eslint-plugin-jsx-a11y": "6.4.1",
     "eslint-plugin-react": "7.21.5",
-    "husky": "4.3.6",
+    "husky": "6.0.0",
     "jest": "26.6.3"
   },
   "dependencies": {}

package-lock.json

@@ -0,0 +1,51 @@
+import { createCanvas, loadImage } from 'canvas';
+import resizeImageWidth from '../resizeImageWidth';
+
+const testImageBeforePath = './src/algorithms/image-processing/seam-carving/__tests__/test-image-before.jpg';
+const testImageAfterPath = './src/algorithms/image-processing/seam-carving/__tests__/test-image-after.jpg';
+
+describe('resizeImageWidth', () => {
+  it('should perform content-aware image width reduction', () => {
+    // @see: https://jestjs.io/docs/asynchronous
+    return Promise.all([
+      loadImage(testImageBeforePath),
+      loadImage(testImageAfterPath),
+    ]).then(([imgBefore, imgAfter]) => {
+      // Original image.
+      const canvasBefore = createCanvas(imgBefore.width, imgBefore.height);
+      const ctxBefore = canvasBefore.getContext('2d');
+      ctxBefore.drawImage(imgBefore, 0, 0, imgBefore.width, imgBefore.height);
+      const imgDataBefore = ctxBefore.getImageData(0, 0, imgBefore.width, imgBefore.height);
+
+      // Resized image saved.
+      const canvasAfter = createCanvas(imgAfter.width, imgAfter.height);
+      const ctxAfter = canvasAfter.getContext('2d');
+      ctxAfter.drawImage(imgAfter, 0, 0, imgAfter.width, imgAfter.height);
+
+      const toWidth = Math.floor(imgBefore.width / 2);
+
+      const {
+        img: resizedImg,
+        size: resizedSize,
+      } = resizeImageWidth({ img: imgDataBefore, toWidth });
+
+      expect(resizedImg).toBeDefined();
+      expect(resizedSize).toBeDefined();
+
+      // Resized image generated.
+      const canvasTest = createCanvas(resizedSize.w, resizedSize.h);
+      const ctxTest = canvasTest.getContext('2d');
+      ctxTest.putImageData(resizedImg, 0, 0, 0, 0, resizedSize.w, resizedSize.h);
+      const imgDataTest = ctxTest.getImageData(0, 0, resizedSize.w, resizedSize.h);
+
+      expect(resizedSize).toEqual({ w: toWidth, h: imgBefore.height });
+      expect(imgDataTest.width).toBe(toWidth);
+      expect(imgDataTest.height).toBe(imgBefore.height);
+      expect(imgDataTest.width).toBe(imgAfter.width);
+      expect(imgDataTest.height).toBe(imgAfter.height);
+
+      // @TODO: Check that images are identical.
+      // expect(canvasTest.toDataURL()).toEqual(canvasAfter.toDataURL());
+    });
+  });
+});