Prevent certain Blend Modes from affecting alpha channel

[raffal1989]

Hello,
I recently purchased Paint Shop Pro and started the process of translating my existing techniques to this new software.
After some time I had most of my workflows translated to PSP and some advanced tools made me really excited about switching to it permanently. Unfortunately one thing is giving me a lot of problems.
When I have a layer with transparent areas, imagine a simple red circle. I would like to add some texture to it so I created a new layer with some procedurally generated clouds lets call it "texture" placed it above my circle and used "Dodge" Blend Mode to lighten some parts of my circle. PSP correctly calculates new values for pixels on my circle but for transparent area it does something I did not expect - passes the value of "texture" the layer to transparent pixels. I tried wrapping texture and circle to a layer group but that got even stranger, transparent pixels became black. I did a small test and when using dodge brush on the same circle, transparent pixels are unaffected, only opaque part is modified.

I know that describing this is pointless so I attached a screenshot of what I am getting in PSP and what I am used to in GIMP.
Regarding the screenshot:
please note that in both programs there are 3 layers,
1. top one with clouds texture
2. middle one with circle on transparent background
3. bottom one with a word HI

My question is, can I somehow enable my desired behaviour ? I know that I can solve this issue with layer mask on the "texture" but then I will have to update it every time I modify my circle's shape

I hope I did not make my post too hectic.

Best Regards,
Rafal

[Jean-Luc]

Could Lock Transparency help you?

[LeviFiction]

No, lock transparency doesn't help as it only locks the layer's transparency and not the entire image. Since the blend mode isn't actually changing the transparency of the layer it can't limit it.

Entertainingly this has the opposite issue in Photoshop. In Photoshop the underlying pixels are ignored when doing the math because they are transparent and so the clouds are what appear around the circle.

So, PSP ignores the transparency altogether in it's calculation, Photoshop only ignores it from the layer it exists on, and GIMP let's it override the math altogether.

I don't know if this is the best way. But it's the only one I can think of.

In PSP you will either have to mask out the area you want ignored or actually delete it from the clouds layer.

Both are easy.
1) select the circle layer.
2) Hit Ctrl+A (select all)
3) Hit CTRL+F (Float selection)
4) Right click on floated layer and select Delete
5) Hit CTRL + SHIFT + I (invert selection)
6) Select clouds layer
7) Layers -> New Mask Layer -> Show Selection

The clouds layer is now masked to match the the circle layer. And this can be scripted for easy repetition.

[raffal1989]

@Jean-Luc: Thanks for the suggestion, unfortunately Transparency Lock does not help with this issue,
@LeviFiction: I was afraid that this is just one of those things that different programs do differently... Thanks for suggested workaround, I will incorporate it into my workflow or develop new one. Luckily so far PSP checks enough boxes for me to accept couple of limitations.

I will post a suggestion in a feature Wish List thread, this seems like easy enough feature to implement.

Regards,
Rafal

[hartpaul]

Or would this work?
1. Choose the circle layer - magic wand - Match Mode All Opaque make selection
2. Choose the top layer - Fill with texture - only circle selection is filled
Gives same result as Gimp

or if you already have a filled texture layer
1. choose circle layer - magic wand - Match Mode All Opaque, make selection, Selections > Invert
2. Choose top texture layer - hit delete , then Selections > Select None