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Let's say you're using the GIMP paintbrush with transparency, or with pressure opacity, with a tablet. If you draw over the same spot multiple times without releasing the mouse button/stylus, GIMP will not add "paint" to it. But if you release MB/stylus and go over that spot again, the "paint" on that spot will double. What I want is for this not to happen.

So basically I want to make GIMP act as if you've never released the mouse button. This could be done by looking at each pixel being drawn on, and setting its opacity to max{current opacity, paintbrush opacity}.

Note: while this can be done by using multiple layers, or by some other hacky method, it would be way too inconvenient for regular use (like digital painting). The goal is to make the paintbrush tool only draw when its opacity exceeds the opacity of the pixel being drawn on.

Thanks!

example

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  • Hi. Welcome to GDSE. What you are trying to do won't work if you have the brush set to have some transparency. Think about it for a moment. You want the brush to be opaque and semi-transparent at the same time. It would need to be fully opaque to cover the brush stroke below. You might want to experiment using Pressure Color paint dynamics, and the FG to BG gradient option instead.
    – Billy Kerr
    Commented Jul 15 at 17:24
  • see example using the mapping matrix Pressure Color setting with a Gradient to control the colours, This is a bit messy as it tends to leave a lighter blob at the end of every stroke as you lift the stylus. So it may not be entirely practical.
    – Billy Kerr
    Commented Jul 15 at 17:36
  • @BillyKerr But what I'm describing does happen, it happens while you're holding down left mouse. To describe it in a way that can easily be implemented: each pixel being drawn on gets the maximum opacity of the two: its current opacity, and the opacity of the brush.
    – gimpuser1985
    Commented Jul 15 at 21:03

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The closest to what you want is "Behind" mode (as a paint tool mode). In that mode the paint tool only fills the transparency, so when you paint over existing lines, nothing happens. But the transparency is filled up to full opacity, so you would have to paint at full opacity on a layer with reduced opacity.

strokes

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