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Add `Sharp.compare(file1, file2, callback)` function for comparing images using mean squared error (MSE). This is useful for unit tests. See: - https://github.com/jcupitt/libvips/issues/291 - http://entropymine.com/imageworsener/resizealpha/
78 lines
2.5 KiB
JavaScript
78 lines
2.5 KiB
JavaScript
'use strict';
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var assert = require('assert');
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var fixtures = require('../fixtures');
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var fs = require('fs');
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var sharp = require('../../index');
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sharp.cache(0);
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// Constants
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var MAX_ALLOWED_MEAN_SQUARED_ERROR = 0.0005;
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// Tests
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describe('sharp.compare', function() {
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it('should report equality when comparing an image to itself', function(done) {
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var image = fixtures.inputPngOverlayLayer0;
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sharp.compare(image, image, function (error, info) {
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if (error) return done(error);
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assert.strictEqual(info.isEqual, true, 'image is equal to itself');
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assert.strictEqual(info.status, 'success', 'status is correct');
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assert(0 <= info.meanSquaredError &&
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info.meanSquaredError <= MAX_ALLOWED_MEAN_SQUARED_ERROR,
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'MSE is within tolerance');
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done();
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});
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});
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it('should report that two images have a mismatched number of bands (channels)', function(done) {
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var actual = fixtures.inputPngOverlayLayer1;
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var expected = fixtures.inputJpg;
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sharp.compare(actual, expected, function (error, info) {
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if (error) return done(error);
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assert.strictEqual(info.isEqual, false);
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assert.strictEqual(info.status, 'mismatchedBands');
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assert(typeof info.meanSquaredError === 'undefined', 'MSE is undefined');
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done();
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});
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});
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it('should report that two images have a mismatched dimensions', function(done) {
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var actual = fixtures.inputJpg;
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var expected = fixtures.inputJpgWithExif;
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sharp.compare(actual, expected, function (error, info) {
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if (error) return done(error);
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assert.strictEqual(info.isEqual, false);
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assert.strictEqual(info.status, 'mismatchedDimensions');
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assert(typeof info.meanSquaredError === 'undefined', 'MSE is undefined');
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done();
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});
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});
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it('should report the correct mean squared error for two different images', function(done) {
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var actual = fixtures.inputPngOverlayLayer0;
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var expected = fixtures.inputPngOverlayLayer1;
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sharp.compare(actual, expected, function (error, info) {
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if (error) return done(error);
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var meanSquaredError = info.meanSquaredError;
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assert.strictEqual(info.isEqual, false);
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assert.strictEqual(info.status, 'success');
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// ImageMagick reports: 42242.5
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// `compare -metric mse 'actual' 'expected' comparison.png`
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assert(41900 <= meanSquaredError && meanSquaredError <= 41950,
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'Expected: 41900 <= meanSquaredError <= 41950. Actual: ' + meanSquaredError);
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done();
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});
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});
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});
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