White background on GIF turns into rgb(252, 254, 252)

[2hoch11]

Resizing a gif with GD library, turns the wite background of the image into a very light gray rgb(252, 254, 252). I fixed that by replacing the gif with a png but that does not fix the problem.

…and yes, I have to use GD and no ImageMagick…

[horst]

Which PHP / GD version?

What are your settings for the image sizer in the site/config.php ? Have you changed the default settings (contained in wire/config.php)?

You may experiment with these settings:

    'defaultGamma' => -1,           // defaultGamma: 0.5 to 4.0 or -1 to disable gamma correction (default=2.0)

    'defaultGamma' => 2.2,           // defaultGamma: 0.5 to 4.0 or -1 to disable gamma correction (default=2.0)

 

[2hoch11]

@horst

PHP: 7.3.21

GD: bundled (2.1.0 compatible)

'quality' => 85,
'sharpening' => 'none',
"forceEngine" => "ImageSizerEngineGD"

Changing the gamma does not affect the result… but I can see that it happens only if the image is scaling UP (and it is a GIF). If it scales down the white color does not change.

[horst]

1 hour ago, 2hoch11 said:

but I can see that it happens only if the image is scaling UP

Uh, how ugly! - Every your settings are looking good. I believe there is no possible solution within the imagesizer itself.

Whats about uploading a bigger original image and don't use / allow upscaling?

[2hoch11]

1 minute ago, horst said:

Uh, how ugly! - Every your settings are looking good. I believe there is no possible solution within the imagesizer itself.

Whats about uploading a bigger original image and don't use / allow upscaling?

Yes, that would be the solution. Maybe IMagick is better but in this case I have to use GD…