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Test that two images are identical for the Seam Carving algorithm. #694

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Merged
merged 5 commits into from
Apr 21, 2021
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Merged

Test that two images are identical for the Seam Carving algorithm. #694

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7cc3d7a
Test that two images are identical for the Seam Carving algorithm.
trekhleb Apr 21, 2021
d428541
Tune the Seam Carving tests.
trekhleb Apr 21, 2021
c89241a
Tune the Seam Carving tests.
trekhleb Apr 21, 2021
0adad2b
Tune the Seam Carving tests.
trekhleb Apr 21, 2021
4b39862
Tune the Seam Carving tests.
trekhleb Apr 21, 2021
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1 change: 1 addition & 0 deletions .husky/pre-commit
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Original file line number Diff line number Diff line change
@@ -1,5 +1,6 @@
#!/bin/sh
. "$(dirname "$0")/_/husky.sh"

# @TODO: Implement the pre-commit checks.
# npm run lint
# npm run test
44 changes: 42 additions & 2 deletions src/algorithms/image-processing/seam-carving/__tests__/resizeImageWidth.test.js
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Expand Up @@ -4,6 +4,40 @@ 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';

/**
* Compares two images and finds the number of different pixels.
*
* @param {ImageData} imgA - ImageData for the first image.
* @param {ImageData} imgB - ImageData for the second image.
* @param {number} threshold - Color difference threshold [0..255]. Smaller - stricter.
* @returns {number} - Number of different pixels.
*/
function pixelsDiff(imgA, imgB, threshold = 0) {
if (imgA.width !== imgB.width || imgA.height !== imgB.height) {
throw new Error('Images must have the same size');
}

let differentPixels = 0;
const numColorParams = 4; // RGBA

for (let pixelIndex = 0; pixelIndex < imgA.data.length; pixelIndex += numColorParams) {
// Get pixel's color for each image.
const [aR, aG, aB] = imgA.data.subarray(pixelIndex, pixelIndex + numColorParams);
const [bR, bG, bB] = imgB.data.subarray(pixelIndex, pixelIndex + numColorParams);

// Get average pixel's color for each image (make them greyscale).
const aAvgColor = Math.floor((aR + aG + aB) / 3);
const bAvgColor = Math.floor((bR + bG + bB) / 3);

// Compare pixel colors.
if (Math.abs(aAvgColor - bAvgColor) > threshold) {
differentPixels += 1;
}
}

return differentPixels;
}

describe('resizeImageWidth', () => {
it('should perform content-aware image width reduction', () => {
// @see: https://jestjs.io/docs/asynchronous
Expand All @@ -21,6 +55,7 @@ describe('resizeImageWidth', () => {
const canvasAfter = createCanvas(imgAfter.width, imgAfter.height);
const ctxAfter = canvasAfter.getContext('2d');
ctxAfter.drawImage(imgAfter, 0, 0, imgAfter.width, imgAfter.height);
const imgDataAfter = ctxAfter.getImageData(0, 0, imgAfter.width, imgAfter.height);

const toWidth = Math.floor(imgBefore.width / 2);

Expand All @@ -44,8 +79,13 @@ describe('resizeImageWidth', () => {
expect(imgDataTest.width).toBe(imgAfter.width);
expect(imgDataTest.height).toBe(imgAfter.height);

// @TODO: Check that images are identical.
// expect(canvasTest.toDataURL()).toEqual(canvasAfter.toDataURL());
const colorThreshold = 50;
const differentPixels = pixelsDiff(imgDataTest, imgDataAfter, colorThreshold);

// Allow 10% of pixels to be different
const pixelsThreshold = Math.floor((imgAfter.width * imgAfter.height) / 10);

expect(differentPixels).toBeLessThanOrEqual(pixelsThreshold);
});
});
});