Is there a way to remap the alpha values/ affect transparency

Questions & Problems
#1

I’m trying to shift all semi transparent pixels to completely transparent. I thought I’d be able to remap the alpha channel but it doesn’t seem to work. Is there a way of doing this? Alternatively is there a way to grow the fill selection by one pixel?

#2

You want an object to fade out to it’s outer edges or something like (no animation, but image)?
You have full control over all alpha plane data if you select this edit mode:
image

Now your color palette turns to gray scales and you can draw on the alpha plane with every drawing tool, apply fills, use the shade paint mode etc.
For the shade paint mode I suggest to select one of the predefined alpha gradients that only contain few alpha entries in a ramp:
image

You then can also pick up alpha plane portions as a brush, remap it to another gradient (defined b yourself) etc. .

Use this icon
image
to show/hide the color layer.

Does this help?

#3

Hi Jan, thanks for the quick response. I’m trying to replicate an old animation technique for colouring outlined artwork. I want to duplicate the linework layer and remove all grey antialiasing /semitransparent pixels, I can then colour the layer extremely quickly and use the linework layer on multiply to reintroduce the antialiasing pixels.

#4

Understood. Please do the following to select all pixels that have an alpha value smaller than 255 (100%).

  1. select the alpha only edit mode as described above
  2. go to menu Paint Mode and select “Selection” there. This increases/decreases the selection when you apply drawing functions on the canvas.
  3. select the flood fill tool. There the “current paint mode” is selected by default as filling method.
  4. disable “Isolated Fill” and use a tolerance of “0”
  5. now apply the fill on a pixel that has 255 $FF as alpha value and fill

Now all fully opaque pixels are selected.

  1. Use menu Selection/Invert. Now all semi transparent pixels are selected.
  2. right click on the “checker pattern” right beside the color selector shapes (top left of main window). This selects “full transparency” as right mouse button color
  3. hit “K” to clear the image. Now all pixels in the selection are erased.

(9. Don’t forget to select normal paint mode again now :slight_smile: )

Does this help?

#5

that’s perfect
thankyou.