I’m using PNGs with transparency in my Program. Als long as I keep them aligned with the pixel-Raster everything is just fine. But when I position something “off-pixel” (e.g. with a translation of 0.5) then I get artifacts at the areas where the Image contains semi-transparent-pixels (e.g. at the borders of visible objects). I’ll attach some files where you can see what I mean.
Problem is, the objects shall be moved over the screen - and that as smooth as possible.
Ideally you want the content of your image to extend 1px each way over the transparency border. What it’s doing here is interpolating to the black around the image as well as interpolating the alpha to 0. If you’ve got an old version of PSP which lets you modify the alpha/RGB 100% seperately this is a piece of cake but PS’s transparency handling is awful.