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import pixelmatch from 'pixelmatch';
export default {
toImageDiffEqual: () => {
const getImageData = (img) => {
const canvas = document.createElement('canvas');
canvas.width = img.width;
canvas.height = img.height;
canvas.getContext('2d').drawImage(img, 0, 0);
return canvas.getContext('2d').getImageData(0, 0, img.width, img.height).data;
};
return {
compare(actual, expected, threshold = 0.1) {
if (actual.height !== expected.height || actual.width !== expected.width) {
return {
pass: false,
message: `Expected image dimensions (h x w) of ${expected.height}x${expected.width}.
Received an image with ${actual.height}x${actual.width}`,
};
}
const { width, height } = actual;
const differentPixels = pixelmatch(
getImageData(actual),
getImageData(expected),
null,
width,
height,
{ threshold },
);
return {
pass: differentPixels < 20,
message: `${differentPixels} pixels differ more than ${
threshold * 100
} percent between input and output.`,
};
},
};
},
};
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