PNGs are sometimes converted to JPGs during export.
To avoid this, you have to select your image the Resources panel and uncheck the ‘optimize at export’ box.
Is there a way to do this for all assets without unchecking them one by one ?
Would love to hear the solution to this one too. Since after export I optimise the PNG with PNGYU to make the file size smaller. In my case JPEG file size larger than PNG.