Concretely, the filter is a per-pixel transform applied to the decoded image, so the file is necessarily re-encoded once — apply every filter you want in a single pass rather than stacking runs. 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. JFIF is a plain JPEG bitstream under the original 1992 interchange header, which is why some viewers show it as a generic image and cameras still emit it. Colour depth and the palette model in particular decide how smoothly a gradient or a blur can be represented.
Anything specific to JFIF to keep in mind?
+
Yes — many editors silently rewrite a JFIF as an ordinary JPEG on save, so keep the original if the .jfif extension itself matters to whatever consumes the file. 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.
