RGB channels changed upon load of RGBA PNG file

[Texel]

When I load a PNG or TGA texture image file that contains RGBA channels which are different, the RGB channels are modified, become black where alpha is zero.

This is destructive and prevents me from working with such files.

Is there a known work around for this?

I've attached a example file (pngtest1.png) which has R,G,B,A channels which do not align perfectly.  When loaded into a viewer such as XnView, extracting each channel independently will show squiggles in R,G,B but a box mask in A.

EDIT: Uploading attachment fails with error -200.

Searching the forum shows some mention of this issue and the reverse of it, creating images with independent R,G,B,A channels.

One such forum thread is "How to Edit the Alpha Channel" https://forum.affinity.serif.com/index.php?/topic/76911-how-to-edit-the-alpha-channel/page/9/

Ideally I'd like to import and export RGBA images with independent channels and edit them by simply masking via the show/edit toggle buttons which almost work how I expect, but do not due to the alpha channel dependency.

[NotMyFault]

Hi and welcome to the forum.

As far as i know this is a known limitation, and there is no real workaround.

You would need to ensure that the alpha values are nonzero before opening the file in Affinity apps. You can set them to the lowest value of 1/255, but as soon as you get 0 the damage will be done.

If my memory serves me correct, it was possible in the past to open such a file, and use channels panel>fill on alpha channel to recover RGB values. Can’t find that older post right now. But if you use any other tool to edit the file before that step, the damage will be done.

Older posts relevant:

[Texel]

That is unfortunate. I am trialing Affinity Photo to find an affordable alternative to Photoshop.

Independent editing of channels both color and alpha is critical, as is editing existing texture files.