PNG files could use some optimisation (again)

[dhouwn]

By using OptiPNG and PNGOUT with the highest optimisation settings I was able to reduce the size of the skin folder of the newest dev build from 89.5 KiB to 71.5 KiB, not much but eh, why not?

[Giorgio Maone]

Are they still 24 bit (with 8 bit alpha channel)?
If so, could you send me your set?

[dhouwn]

Oops, indeed some were already PNG8s and some turned then into PNG8s by OptiPNG which should have only happen if the conversion lossless (ie. the source images had <= 2^8 colours and only binary transparency), is this an issue?

Also wouldn't it be better if those tools were rather included in your build configuration, so that you have the optimisations even if you add/change the images in the future? The re-compression does not take that long on such small images.

[Giorgio Maone]

Oops, indeed some were already PNG8s and some turned then into PNG8s by OptiPNG which should have only happen if the conversion lossless (ie. the source images had <= 2^8 colours and only binary transparency), is this an issue?

They definitely don't have binary transparency, because their color/transparency borders are antialiased.
If I turned them into PNG8 you would see trashed contours, especially on dark themes.

[dhouwn]

It's actually both PNGOUT and OptiPNG that try make convert images such as yu-glb16.png into the PNG8 format but for latter at least there's a command line option "-nx" to stop these allegedly lossless reduction methods.
So, with just using OptiPNG with "-nx -o7" on all PNG files I was still able to reduce the size to 83.4 KiB which of course is even more negligible and considering that one apparently can't trust the claims about losslessness (what a word ) it might be better to forget about this altogether.