Bug 492198

*What*
Add an option for the 'effort'/encode speed of image codecs that use this

*Why*
So you may choose the tradeoff between speed and size, sometimes codecs may have significant space savings with minimal speed cost at a setting or two slower than default

as an example, i find a lossless effort 8 jxl can be quite significantly smaller than the default effort 7

*Other*
looking at the QT library used for image saving, it *seemingly* does not expose this option, so i'd understand if this feature request is more effort than it's worth

and, sorry if this is a duplicate, i haven't quite figured out this issue tracker software