Designer 2.4.2 — blend mode color burn visible on transparent background

[Viktor CR]

A rectangle with blend mode "color burn" over a transparent area
– where, just like on white, no color, that could be burned, exists –
is visible as the plain color.

It should be transparent, correct?
Otherwise, I'd need to create very complex layer masks in practice, to achieve transparency in spots without objects, that are actually meant to remain transparent.

Same goes for other blend modes, but especially with "color burn", where you rely on the effect to only affect spots with existing color, it doesn't make sense to get the 100% color surface, still.

See attached also the example file.

Color Burn over transparent issue.afdesign

[Brian_J]

The blend mode is behaving the way I’d expect it to. My assumptions…

White is a color, so the blend mode is interacting with white. A layer with no color beneath it (transparency) doesn’t have a color to interact with, so blend modes won’t effect the object’s color.

[KarlLegion]

I don't know if other software works in the same way, but just like Brian said, it's the normal behavior of Affinity Suite. 

On 4/8/2024 at 10:21 PM, Viktor CR said:

Otherwise, I'd need to create very complex layer masks in practice, to achieve transparency in spots without objects, that are actually meant to remain transparent.

For the example you showed here, you can nest the rectangle under the circle. No complex layer masks are needed.

[Old Bruce]

On 4/8/2024 at 7:21 PM, Viktor CR said:

It should be transparent, correct?

Why? It appears over the transparent background as though nothing was under it. All the blend modes with the exception of Erase show the rectangle exactly the same. It is there with the colour it has. The white area is not showing the colour burning rectangle as invisible, the colour burning rectangle is actually colour burning the underlying white to white.

[Viktor CR]

On 4/11/2024 at 9:48 PM, Old Bruce said:

the colour burning rectangle is actually colour burning the underlying white to white

I disagree. The color burning rectangle is trying to burn the white, but as that has no color CMYK[0/0/0/0], it doesn't succeed.
Same intuitive expectation would apply to transparency: If there's nothing to burn, it shouldn't be burned.

Of course I also realize, the algorithm for this blend mode doesn't strictly work like that, but probably first subdivides paths.

[Viktor CR]

On 4/11/2024 at 7:03 PM, KarlLegion said:

you can nest the rectangle under the circle. No complex layer masks are needed.

Yes, indeed — however, I have a complex object configuration here and not just a single layer.

The following is, what I've found, works:
I've collected the target objects in a Symbol and apply that as a complex mask to the rectangle, to remove what's transparent from the overlaying color-burn object.

[Viktor CR]

Question for Affinity staff

Can you confirm, it is a valid expectation to want
blend modes in some circumstances not apply in transparent areas and thus not appear there, at all?

It is possible, that a sort of "isolate blending" option for groups may solve this issue in a more deterministic way.

I am curious about your developers' view.

[KarlLegion]

22 hours ago, Viktor CR said:

The following is, what I've found, works:

Good to hear that you find a way to work it around.🙂

Then, here's my opinion about your expectation. (It's just an "exchange of ideas". I know, it's unimportant and you're seeking for an official opinion. So, I'm not going to stop you from making a feature request.)

For what you said:

22 hours ago, Viktor CR said:

but as that has no color CMYK[0/0/0/0], it doesn't succeed

Let's see it this way: For RGB colour model, white is actually 255,255,255 which is, on the contrary, full of colour. So, don't be fooled by the name, it's nothing about colour. (The same for Colour Dodge. Even Black (as a base layer) is "full of colour" in CMYK model, the top layer can't dodge anything.)

It calls "Blend Mode" for a reason, because it blends colour. It needs 2 layers for it to blend (except Erase). If there's no colour for it to blend with, it's reasonable to expect that the top layer will have no changes at all. The same for the case that the base layer being transparent — the top layer will have no changes.

From Wikipedia: "The Color Burn mode divides the inverted bottom layer by the top layer, and then inverts the result."

So, the top layer basically amplifies the "darkness" of the base (bottom) layer — if the base layer is 100% white ("darkness" = 0), there will be nothing for it to amplify (0÷n=0). So, the both layers will have no changes. And also, the calculation is all about the base layer, so if there are no base layers in the first place, then there won't have any calculations at all. It means, no changes also.

What you expect, is like seeing the top layer as a filter more than an actual object (i.e. a layer applying effect to the bottom layer without it having actual pixels)

Would you mind sharing the file of your project in question? I'm just curious about your actual problem and the method you used to solve it. I like puzzles. 😉

(BTW, you can make your suggestions in the Feedback & Suggestions board instead.)

 

[walt.farrell]

10 hours ago, Viktor CR said:

The color burning rectangle is trying to burn the white, but as that has no color CMYK[0/0/0/0],

I think that's the first you've mentioned CMYK, which adds other considerations as the Blend Modes are defined based on additive RGB processing, not subtractive CMYK processing, and may behave differently than you would expect when used in CMYK. I don;'t think that's the reason for what you're asking about here, just something to be aware of.

E.g.,