XF 2.3 The quality of uploaded, optimized images is poor

[Old Nick]

I have enabled image optimization to Webp but am currently using PHP built-in GD image library (while waiting for my host to enable support for Webp with imagick), is this the cause of this?
Thanks.

 

[Mr Lucky]

My understanding is the the main difference with Imagick is in regard to thumnbnails.

I am finding the opposite, ie I would prefer the webp compressed more than it does but this is probably all down to personal preference and maybe I have a less discerning eye.

Presumably you have directly compared before and after

 

[Old Nick]

My understanding is the the main difference with Imagick is in regard to thumnbnails.

Good point

I just raised the maximum image dimensions from 800x800 to 1200x1200 and the difference is clear, I think it came from here.

 

[Mr Lucky]

Note that the default compression is 85%. Chris D has mentioned that this can now be changed in the config.php file by adding

PHP:
$config['maxImageResizeQuality'] = 85;

and raising the (or lowering) the number. sadly there is no one-size-fits-all as the optimum can vary depending on the image itself.

 

[Old Nick]

and raising the (or lowering) the number. sadly there is no one-size-fits-all as the optimum can vary depending on the image itself.

Thank you for this clarification. I don't think I will change this number; I will trust the XF team and keep it at 85%.

 

[Mr Lucky]

It's probably safest. I use webp compression when exporting from Affinity Photo, and using the preview some images can go as low as 30 with no significant degradation (to my eyes) but others need at least 70. I have worked out why this is but maybe due to numbers different hues apposed to differing shades of the same hue.

 

[zappaDPJ]

maybe due to numbers different hues apposed to differing shades of the same hue.

That sounds like image posterization, where the converted image loses continuous graduation of tone to several areas of fewer tones. My unscientific impression is that it seems to occur more often with webp than jpg.

 

[Arantor]

WebP is more aggressive about it, in ways JPEG isn’t. JPEG primarily does a much more localised back-and-forth to analyse differences, while WebP can do this on a much larger scale and in different directions, with the result that it will consider larger blocks of gradual tonal change to be much closer and therefore more aggressively compress them.

 

[Mr Lucky]

I've just optimised my test site images at compression:35. Attachments directory went down from 2.58GB to 658MB and the pictures don't seem to have suffered in any significant way.

 

[Chromaniac]

hehe yeah. i changed the xf setting to 15 and uploaded a bunch of images. they were blurry but still quite nice. but yeah set it back to default 85 because text image are going to get ruined at low setting.

 

[Mr Lucky]

from 2.58GB to 658MB

Ooops Sorry. I originally said reduced to 65MB, that was a typo it was 658MB but still very impressive given the quality was not affect as far as I could see.