I have a simple, 200x200 PNG. I need to have it in 358 more hues. I could save 358 copies of the same picture in Paint.NET, manually adjusting, but that's a bit silly. Is there some sort of web app that would do this for me? Does Photoshop have a feature that could do this?
You can script this in Photoshop actions; record an action that does a Hue/Saturation/Lightness adjust incrementing the hue by 1 degree, then save the file. You can duplicate these two actions as many times as you need in the Action pane. After 360 adjustments, you should be back where you started...