Webp has Yellow Tint on Scanned Images Produced with GIMP

[Flint Stone]

I scanned my old secondary textbooks so that I can throw them away to save some space. PNGs are produced by Canon Scan Utilities and are then imported into GIMP and edited. It is then exported into Webps at q90. I accidentally found out (by switching layers/alt+tabbing) that there is quite an obvious yellow tint on the image after converting into webps. And on the contrary, exporting into Jpegs at 75 (roughly same file sizes) have better results and the color distortion is much less obvious even with direct comparison (by switching layers in GIMP/alt+tabbing)

I also found some discoloration when using webp at 90 but to much less extent when using JPEG at 75

That yellow tint & discoloration on some other pages can ONLY be fixed  with lossless enabled but cannot be fixed even at q98.

I used webp solely because of its smaller file sizes. But if JPEG can perform even better at roughly the same size, then there is no point using it since JPEG even has better support by other software (especially on mobile environment)

 

[Flint Stone]

Update to Label the format of each image 

Original  PNG

JPG at 75

Webp isn't supported by Google itself to be uploaded as image....

[James Zern]

Thanks for the report. Would you mind filing a bug [1] and include the png, jpeg and webp?

[1] https://bugs.chromium.org/p/webp/issues/entry

On Wed, Feb 9, 2022 at 5:47 PM Flint Stone <flintst...@gmail.com> wrote:

Update to Label the format of each image 

Original  PNG

JPG at 75

Webp isn't supported by Google itself to be uploaded as image....

Was this through the groups UI or somewhere else?

 

On Thursday, February 10, 2022 at 8:44:18 AM UTC+8 Flint Stone wrote:

I scanned my old secondary textbooks so that I can throw them away to save some space. PNGs are produced by Canon Scan Utilities and are then imported into GIMP and edited. It is then exported into Webps at q90. I accidentally found out (by switching layers/alt+tabbing) that there is quite an obvious yellow tint on the image after converting into webps. And on the contrary, exporting into Jpegs at 75 (roughly same file sizes) have better results and the color distortion is much less obvious even with direct comparison (by switching layers in GIMP/alt+tabbing)

I also found some discoloration when using webp at 90 but to much less extent when using JPEG at 75

That yellow tint & discoloration on some other pages can ONLY be fixed  with lossless enabled but cannot be fixed even at q98.

I used webp solely because of its smaller file sizes. But if JPEG can perform even better at roughly the same size, then there is no point using it since JPEG even has better support by other software (especially on mobile environment)

 

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[Flint Stone]

Thanks for your help!

Form submitted.

https://bugs.chromium.org/p/webp/issues/detail?id=555

Was this through the groups UI or somewhere else?

Yes, Google Groups

[James Zern]

On Wednesday, February 9, 2022 at 9:31:11 PM UTC-8 flintst...@gmail.com wrote:

Thanks for your help!

Form submitted.

https://bugs.chromium.org/p/webp/issues/detail?id=555

Was this through the groups UI or somewhere else?

Yes, Google Groups

Thanks for confirming. I filed a bug internally to address this.

[Pascal Massimino]

Hi,

thanks for the report (and the interesting problematic sample!). As James mentioned in the bug, using sharp_yuv by default will help overcome the limitations of yuv420 internal format.

For definiteness, i attach the result of using 'cwebp -sharp_yuv -q 90 ...' on your input.

Unfortunately, the 'sharp-yuv' option is not exposed in the GIMP UI. Maybe we should file a feature request there...

hope it helps,

skal/

 

 

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