Compares 2 images for similarity, returning a percentage of the difference (0-1)
npm install compare-image --save
There are 2 buit in comparission methods:
###comparePixels (imgA, imgB, cb(error, diff) )### checks each pixel for any differences - best for visual comparison. Diff is the percentage difference as 0-1.
###compareByChannels (imgA, imgB, cb(error, diff)### checks each channel on each pixel - best for comparing the underlyin data. Diff is the percentage difference as 0-1.
###compare (imgA, imgB, comparator(bitmapA, bitmapB), cb(error, diff) )###
Compare allows you to run your own comparator function. This will receive 2 args, each a ndarray of pixels in raster order having shape equal to [width, height, channels]
comparator must return the difference between the two bitmaps as value of 0-1.
##pixels vs channels## If we take 2 images, and the only difference is the RED channel on 1 pixel.
comparePixels looks at each pixel as a whole. Any change is treated as a visual difference of that pixel. So a 100 x 100px image, which has 1 pixel different would be 0.1 percent different.
compareData would produce only a 0.025 percent difference for same image, as only 1 of the 4 channels on that pixel was different.
see here.
#Usage
var compareImg = require('compare-image');
//can a relative path, an http url, a data url, or an in-memory Buffer.
var imgA='http://www.domain.com/path/to/image.png';
var imgB='http://www.domain.com/path/to/image.png';
compareImg.comparePixels(imgA, imgB, function(err, diff) {
console.log("the images are", diff, " percent different");
});