Posterous theme by Cory Watilo

Filed under: image

Gamma error in picture scaling

There is an important error in most photography scaling algorithms. All software tested have the problem: The Gimp, Adobe Photoshop, CinePaint, Nip2, ImageMagick, GQview, Eye of Gnome, Paint and Krita. Also three different operating systems were used: Linux, Mac OS X and Windows. These exceptions have subsequently been reported: the Netpbm toolkit for graphic manipulations, the developping GEGL toolkit, 32 bit encoded images in Photoshop CS3, the latest version of Image Analyzer, the image exporters in Aperture 1.5.6, the latest version of Rendera, Adobe Lightroom 1.4.1, Pixelmator for Mac OS X and Paint Shop Pro X2.

Photographs that have been scaled with these software have been degradated. The degradation is often faint but probably most pictures contain at least an array where the degradation is clearly visible. I suppose this happens since the first versions of these software, maybe 20 years ago.

A photograph of His Holiness the Dalai Lama was tuned to exploit the problem. If you want to give it a try then scale it down 50% using your best software. (If you cannot download the image to your computer by right-clicking on it then either make a snapshot of the screen or download the image in this zipped file.)

The Dalai Lama

This is what you probably will get once the image is scaled by your software:



How much did you pay for that software? This is a scaling performed by a correct software, which evidently shows the same as the start image: