Can I change the transparency of a selection keeping the relative transparency each part already has proportional?
I want to give the middle full opacity but let the border effect that is already existing.
Each layer in GIMP can have the transparency for each pixel specified in two ways, that add to each other:
If you imported a PNG file with transparency, you background layer already has an alpha channel - you can keep that untouched -
Just right click on the layerÅ› thumb on the Layers Dialog
ctrl + L and pick
Add Layer Mask - that way a mask is created. It behaves as a grayscale image, where black means transparency and white means opacity - you can select if you are painting on the actual layer or on its maks by clicking on the respective thumbnails -
Just select the mask and paint it gray (by dragging and dropping a shade of gray on the canvas, or using the bucket fill) - and you have extra, prortional transparency for the whole image, without touching the original transparency levels.