10-27-10 - Image Comparison - JPEG-XR

I'm testing JPEG-XR (aka HD Photo, aka PTC, aka WPF or WIC codec) using the maximum-size chunk width option and with the optional arithmetic coder (instead of the faster RLE/Rice type coder), both of which are supposed to give me maximimum quality/compression. I let it do its color conversion (I believe they use the lossless YCoCg).

On the PDI 1200 image :

On the plus side, the RMSE chart reveals that their color conversion & such code is not just broken the way it is in so many coders.

On the minus side, the SSIM SCIELAB score is just *abysmal* at the crucial area of logbpp = 0 , even worse than Hipix, and in fact much worse than good old JPEG-Huff. The bad perceptual score is confirmed by personal evaluation - JPEG-XR seems to be just the worst of both worlds, it is *both* ringy like JPEG and blurry like JPEG-2000, plus it has a new type of artifact, a kind of blobby ringing (if you are familiar with lapped transforms you have seen these before).

It's just by far the worst thing I've seen yet and it's not even close. Here's the image : PDI JPEG-XR 116,818 bytes

The only thing going for JPEG-XR is that they standardized adding alpha channels, color spaces and HDR. Of course as others have pointed out you could have just added that to JPEG.

BTW the JPEG XR Wikipedia Page reads like an advertisement and should be edited. In particular "JPEG XR file format supports higher compression ratios in comparison to JPEG for encoding an image with equivalent quality." is manifestly not true.

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