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WebP is lossy. Google provides a gallery of images here: http://code.google.com/speed/webp/gallery.html http://code.google.com/speed/webp/gallery.html Basicall

WebP is lossy. Google provides a gallery of images here: http://code.google.com/speed/webp/gallery.html http://code.google.com/speed/webp/gallery.html Basically, they are using predictive coding to achieve good lossy compression. However, I agree, I would also like to see double blind studies on the quality degradation.

jjcm 16y ago
That's great that they have the sample gallery, but without a lossless source (e.g. a control group) to compare it to the gallery that they show counts for nothing. I grabbed the source for it, I'll see if I can do a jpg/webp/png side by side with some analytical data as well.
- jjcm 16y ago
  Update: Here's some very basic file comparisons. Special thanks to Erik Anderson of http://divineerror.deviantart.com http://divineerror.deviantart.com for the lossless images. In the folder is the original image, the compressed version of the image in both jpg and webp, and a enhanced difference map between the compressed version and the lossless image. http://jjcm.org:8081/webp http://jjcm.org:8081/webp Basic analysis shows that right now webp has better preservation of luminance, but at the expense of hue/color. I'll have a blog post up in a bit with a myriad of file tests, difference maps, percentage differences, and hue offsets in a bit.
  - astrange 16y ago
    You shouldn't get any kind of percentage differences in the color channels, at any size above 8x8 blocks in the image. If the entire image is offset that most likely shows a bug in your conversion process.
  - Groxx 16y ago
    Awesome set of pictures. I can live with the squares of WebP better than the hugely-visible gradients of JPEG, methinks. Subjectively, I'd say those images show it to be definitely superior, by a pretty large margin. Very impressive. I can easily live with the 2x decode / 8x encode with those results. edit: though, if there's no alpha capabilities, count me out. Yes, that's my deciding factor.
    - jjcm 16y ago
      Don't jump on it yet, alpha capabilities aren't the only thing that it's missing. After some analysis it doesn't support color profiles - greyscale being the biggest factor here. About to upload a sample black and white image, and you'll see the issues there.
      - Groxx 16y ago
        I was wondering if profiles might have been the reason for some of the larger hue/sat differences (over the whole image). Will gladly keep looking, it's interesting either way :) Thanks!
    - asmosoinio 16y ago
      "We plan to add support for a transparency layer, also known as alpha channel in a future update." http://blog.chromium.org/2010/09/webp-new-image-format-for-web.html http://blog.chromium.org/2010/09/webp-new-image-format-for-w...
  - jjcm 16y ago
    Update 2: Here's the blog post along with mean delta values for both RGB and Luminance from the source image: http://news.ycombinator.com/item?id=1746621 http://news.ycombinator.com/item?id=1746621

jjcm 16y ago

That's great that they have the sample gallery, but without a lossless source (e.g. a control group) to compare it to the gallery that they show counts for nothing. I grabbed the source for it, I'll see if I can do a jpg/webp/png side by side with some analytical data as well.

jjcm 16y ago
Update: Here's some very basic file comparisons. Special thanks to Erik Anderson of http://divineerror.deviantart.com http://divineerror.deviantart.com for the lossless images. In the folder is the original image, the compressed version of the image in both jpg and webp, and a enhanced difference map between the compressed version and the lossless image. http://jjcm.org:8081/webp http://jjcm.org:8081/webp Basic analysis shows that right now webp has better preservation of luminance, but at the expense of hue/color. I'll have a blog post up in a bit with a myriad of file tests, difference maps, percentage differences, and hue offsets in a bit.
- astrange 16y ago
  You shouldn't get any kind of percentage differences in the color channels, at any size above 8x8 blocks in the image. If the entire image is offset that most likely shows a bug in your conversion process.
- Groxx 16y ago
  Awesome set of pictures. I can live with the squares of WebP better than the hugely-visible gradients of JPEG, methinks. Subjectively, I'd say those images show it to be definitely superior, by a pretty large margin. Very impressive. I can easily live with the 2x decode / 8x encode with those results. edit: though, if there's no alpha capabilities, count me out. Yes, that's my deciding factor.
  - jjcm 16y ago
    Don't jump on it yet, alpha capabilities aren't the only thing that it's missing. After some analysis it doesn't support color profiles - greyscale being the biggest factor here. About to upload a sample black and white image, and you'll see the issues there.
    - Groxx 16y ago
      I was wondering if profiles might have been the reason for some of the larger hue/sat differences (over the whole image). Will gladly keep looking, it's interesting either way :) Thanks!
  - asmosoinio 16y ago
    "We plan to add support for a transparency layer, also known as alpha channel in a future update." http://blog.chromium.org/2010/09/webp-new-image-format-for-web.html http://blog.chromium.org/2010/09/webp-new-image-format-for-w...
- jjcm 16y ago
  Update 2: Here's the blog post along with mean delta values for both RGB and Luminance from the source image: http://news.ycombinator.com/item?id=1746621 http://news.ycombinator.com/item?id=1746621