Concretely, the per-pixel transform is applied and written back losslessly, so you can iterate on a look as many times as you like without accumulating any compression damage. You pick the effect and its strength and the transform is applied to the whole file at once.
Which effects are available?
+
Grayscale, sepia, invert, blur, sharpen, and brightness, contrast and saturation adjustment. They can be combined, and combining them in one pass is better than running the tool repeatedly.
Does the source format change how a filter looks?
+
It can. PNG is lossless DEFLATE with a full 8-bit alpha channel and optional 16-bit depth, so it never degrades on re-save but gets large on photographic content. Colour depth and the palette model in particular decide how smoothly a gradient or a blur can be represented.
Anything specific to PNG to keep in mind?
+
Yes — there is no quality slider to get wrong — a PNG round-trips bit-exactly, so the only thing edits cost you is file size. That is often the difference between an effect looking clean and looking banded.
Can I undo a filter after downloading?
+
No — the effect is baked into the output pixels, which is the point of applying it. Keep the original file; that is your undo. Grayscale and blur in particular discard information that genuinely cannot be recovered.
Can I apply the same look to a whole set?
+
Yes. One filter configuration is applied across the batch, which is how you get a visually consistent gallery rather than a set of individually-tweaked images that almost match.
