Image Error Level Analysis with HTML5

written by Jonas Wagner, on 4/15/12 4:40 PM.

Image error level analysis is a technique that can help to identify manipulations to compressed (JPEG) images by detecting the distribution of error introduced after resaving the image at a specific compression rate. I stumbled across this technique in this presentation by Neal Krawetz and decided to do a quick implementation in JavaScript.

How to use this tool

To analyse an image simply drag and drop it onto the page (requires a modern browser like firefox or chrome). Then play with the quality slider to spot anomalies in the error level. The image I analyzed in the screenshot above is a picture of myself that I modified in GIMP. As you can see the error level on the fake part is quite significantly higher than on the rest of the image. There are no such anomalies on the original.

Having that said the algorithm is not exactly reliable, especially with images that have been rescaled and compressed often/intensely. So take it with a pinch of salt and feel free to have a look at the simple source code.

High-performance Particles on a Canvas

written by Jonas Wagner, on 10/6/11 9:20 PM.

View Demo

Some of you might remember my Chaotic Particles demo from last year. That demo was featuring 10'000 particles on a plain old 2d canvas. I decided to optimize that demo a bit in order to support 100'000 particles. I also fixed a little issue where numeric inaccuracy allowed particles to escape and made the influence map more fine grained.

Want to see the source? Just use view source and feel free to ask questions.

Next up: 4'000'000 Particles using WebGL.