White in darken masks is sometimes transparent, sometimes not

[jtlapp]

I have an image that includes bitmask texture layers that are restricted to curves. These layers are essentially halftones in white and black pixels only. I have set them to Darken.

I also have a square in the background (the bottom layer) providing a background color.

When the background square is visible, that color shows through pixels that are white in the bitmasks.

When the background square is hidden, instead of getting the transparent background color, I get white.

It's possible that this is working as designed, but it is unintuitive -- deceptive even. If a layer's color shows through layers above it, I assume that the layers above have transparency. If I remove the underlying color, I assume that I get transparent pixels. But that's not the case. I only discovered this when exporting my final image to PNG.

So now I have to go back through all my masks making them black on transparent, because it wasn't apparent that I had to do this from the beginning.

(You can reproduce this in the file I uploaded earlier. My background layer is set to "passthrough" there, but the problem exists even if you change it back to "normal.")

[Dan C]

Hi jtlapp

The texture layer that is clipped by the curve is a full pixel layer with non transparent properties (ie not a PNG/TIFF), the white that shows when your background colour is off is part of that image layer. Setting the blend mode to darken allows the colour from the background layer below to passthrough the pure white section of the pixel layer, but the white still exists and this is why you don't see the transparent background with the background layer hidden. Blend modes are essentially meaningless if no object exists below that layer (other than erase).

You can however remove the white pixels in the texture layer easily in Affinity Photo, simply select the pixel layer in the layers studio then go to Filters>Colours>Erase White Paper. You should now see the transparent background through this pixel layer using any blend mode, other than erase. I hope this helps!

[jtlapp]

3 minutes ago, Dan C said:

[...] Blend modes are essentially meaningless if no object exists below that layer (other than erase).

You can however remove the white pixels in the texture layer easily in Affinity Photo, simply select the pixel layer in the layers studio then go to Filters>Colours>Erase White Paper. You should now see the transparent background through this pixel layer using any blend mode, other than erase. I hope this helps!

Ah! Then it's my misunderstanding. Thanks for explaining. And thank you for the quick fix!