blockhash/test/tests.js

Perceptual image hash calculation tool

/* global describe, it, JpegImage */

'use strict';

var expect = require('expect.js');
var glob = require('glob');
var path = require('path');
var fs = require('fs');

var blockhash = require('..');

var PNG = require('png-js');
var jpeg = require('jpeg-js');

var testFiles = glob.sync('test/data/*.jpg')
    .concat(glob.sync('test/data/*.png'));

testFiles.forEach(function(fn) {
    describe(fn, function(){
        var ext = path.extname(fn);
        var basename = path.basename(fn, ext);
        var bits = 16;

        [1, 2].forEach(function(m) {
            it('method' + m, function(done) {
                var data, getImgData, hash, expectedHash;

                data = new Uint8Array(fs.readFileSync(fn));

                switch (ext) {
                case '.jpg':
                    getImgData = function(next) {
                        next(jpeg.decode(data));
                    };
                    break;

                case '.png':
                    getImgData = function(next) {
                        var png = new PNG(data);
                        var imgData = {
                            width: png.width,
                            height: png.height,
                            data: new Uint8Array(png.width * png.height * 4)
                        };

                        png.decodePixels(function(pixels) {
                            png.copyToImageData(imgData, pixels);
                            next(imgData);
                        });
                    };
                }

                getImgData(function(imgData) {
                    hash = blockhash.blockhashData(imgData, bits, m);

                    expectedHash = fs.readFileSync("test/data/" + basename + "_" + bits + "_" + m + ".txt", {
                        encoding: 'utf-8'
                    }).split(/\s/)[1];

                    // use hamming distance to iron out little
                    // differences between this jpeg decoder and the one in PIL
                    var hd = blockhash.hammingDistance(expectedHash, hash);
                    expect(hd).to.be.lessThan(3);

                    done();
                });
            });
        });
    });
});