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';
+importresizeImageWidthfrom'../resizeImageWidth';
+
+consttestImageBeforePath='./src/algorithms/image-processing/seam-carving/__tests__/test-image-before.jpg';
+consttestImageAfterPath='./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
+returnPromise.all([
+loadImage(testImageBeforePath),
+loadImage(testImageAfterPath),
+]).then(([imgBefore,imgAfter])=>{
+// Original image.
+constcanvasBefore=createCanvas(imgBefore.width,imgBefore.height);
+constctxBefore=canvasBefore.getContext('2d');
+ctxBefore.drawImage(imgBefore,0,0,imgBefore.width,imgBefore.height);
+constimgDataBefore=ctxBefore.getImageData(0,0,imgBefore.width,imgBefore.height);
+
+// Resized image saved.
+constcanvasAfter=createCanvas(imgAfter.width,imgAfter.height);
+constctxAfter=canvasAfter.getContext('2d');
+ctxAfter.drawImage(imgAfter,0,0,imgAfter.width,imgAfter.height);
+
+consttoWidth=Math.floor(imgBefore.width/2);
+
+const{
+img: resizedImg,
+size: resizedSize,
+}=resizeImageWidth({img: imgDataBefore, toWidth });
+
+expect(resizedImg).toBeDefined();
+expect(resizedSize).toBeDefined();
+
+// Resized image generated.
+constcanvasTest=createCanvas(resizedSize.w,resizedSize.h);
+constctxTest=canvasTest.getContext('2d');
+ctxTest.putImageData(resizedImg,0,0,0,0,resizedSize.w,resizedSize.h);
+constimgDataTest=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());
+});
+});
+});