Editing RGBA channels separably

[mangojambo]

Hello,

I'm testing designer and photo and planning to buy both. I'm checking if it will help in my workflow. My art surrounds game art needs: 3d, animation, lighting, texturing, shading, UI, etc. So I need a lot of maps. Bellow there is an example of a (weird) button and the maps I need to export for my shader. The thing is I will develop it in designer and I need to combine it again in photo. I was using Krita + Gimp. Krita have an amazing feature to set a layer or group layer to influence only a specific channel. This would be perfect if Krita would know how to deal with alpha channel (long story, already talking to developers). So I export the combined RGB image, open in Gimp, add the last map to Alpha channel and export again. Done. I could do it in Blender as well using composite nodes, but I guess it would complicated if I needed some small editing as well. Oh, Photoshop I can just copy a layer, hide it and paste in the channel as if it was a layer as well. Pretty obvious and straight forward, btw.

So the answer is: How can I accomplish this task in Affinity Photo? What kind of workflow would I follow here to edit channels independently? I think this and no game / texture presets, but mostly this is holding my buying back. 

Cheers.

[mangojambo]

Anyone? Please?

[Callum]

Hi MangoJambo,

Welcome to the forums

I'm not sure if I have understood your question correctly but the below thread may help you with this. 

 

Thanks

C

[lepr]

On 3/27/2020 at 1:59 PM, mangojambo said:

Anyone? Please?

A problem for you will be that the current Affinity apps set R, G and B to zero wherever alpha is zero in an exported RGBA image.

[mangojambo]

Hello. Big thanks for both answers!

9 hours ago, Callum said:

Hi MangoJambo,

Welcome to the forums

I'm not sure if I have understood your question correctly but the below thread may help you with this. 

 

Thanks

C

It worked. I followed the image tutorial from that link: 

The channel clear part didn't work when I moved all images as channels, even trying to rasterize. There was no such option, only for the original image. So I had to open each image on its own tab to be able to clear, then copy and paste to the first image. I did set up the alpha as well, giving me this result:

But, as @anon2 pointed, I lost RGB information, so it still useless for me. Alpha channel mask should never mess with RGB channel, only Alpha. Well, the best option could be to have an option to choose, since I can imagine some scenarios where it requires to work as it already is as well.

I both Affinity Designer, it was in my radar from a while ago.  And I'm happy with it. Being able to export sprites in different folders in one time is quite amazing! Now I'm not sure about Affinity Photo yet. Kinda cool the personas, but, I don't know. Affinity have some great templates and all, but none of them are focus in game development. At least yet.

Thanks again for the help and tips.

Cheerios

Edited March 30, 2020 by mangojambo

[valdyr]

On 3/29/2020 at 9:33 PM, anon2 said:

A problem for you will be that the current Affinity apps set R, G and B to zero wherever alpha is zero in an exported RGBA image.

Will this be fixed do you know? Seems that wherever the alpha is 0 also the operations on other channels are not working correctly. For example, i was trying to gauss blur only the blue channel, and where the alpha is 0 the blur didn't affect the image.
And that with forcing RGB to 0 if A is 0 is also a big issue if you use channels as maps for something.

I understand that alpha originally meant as transparency for an image, but now there are different usages for it.

Edited April 30, 2021 by valdyr

[lepr]

Hi and welcome to the Affitity forums

 

39 minutes ago, valdyr said:

Will this be fixed do you know?

We users are told nothing about planned changes and fixes.

 

42 minutes ago, valdyr said:

Seems that wherever the alpha is 0 also the operations on other channels are not working correctly. For example, i was trying to gauss blur only the blue channel, and where the alpha is 0 the blur didn't affect the image.

Sounds like you disabled editing of the Composite Alpha channel when isolating the Composite Blue channel. Ensure both Composite Alpha and Composite Blue are enabled for editing (pencil icon).

 

44 minutes ago, valdyr said:

And that with forcing RGB to 0 if A is 0 is also a big issue if you use channels as maps for something.

If you use a Mask layer at the top of the layer stack as the alpha, and perform no edit that sets alpha to zero in pixels of lower layers, then an exported RGBA image (PNG, TGA or TIFF) will have intact RGB. Well, that's slightly better than absolutely nothing, lol.

[valdyr]

On 4/30/2021 at 4:40 PM, anon2 said:

Hi and welcome to the Affitity forums

 

We users are told nothing about planned changes and fixes.

 

Sounds like you disabled editing of the Composite Alpha channel when isolating the Composite Blue channel. Ensure both Composite Alpha and Composite Blue are enabled for editing (pencil icon).

 

If you use a Mask layer at the top of the layer stack as the alpha, and perform no edit that sets alpha to zero in pixels of lower layers, then an exported RGBA image (PNG, TGA or TIFF) will have intact RGB. Well, that's slightly better than absolutely nothing, lol.

Hey! Thank you for the reply! (even though I've resurected an old thread xD)

But if I enable both Composite Alpha and Composite Blue then they both get blurred. And if I disable editing the Alpha then Blue channel bluring won't be applied at places where Alpha is 0.. Hm the solution as you said is to have a small value in Alpha always (instead of 0)... Yea better that than not being able to edit other channels...

Thanx!

 

[lepr]

4 hours ago, valdyr said:

Hm the solution as you said is to have a small value in Alpha always (instead of 0)

I certainly did not say that!

[lepr]

4 hours ago, valdyr said:

But if I enable both Composite Alpha and Composite Blue then they both get blurred.

Yes, sorry, I misunderstood the problem.

 

Edited May 3, 2021 by anon2

[lepr]

4 hours ago, valdyr said:

But if I enable both Composite Alpha and Composite Blue then they both get blurred. And if I disable editing the Alpha then Blue channel bluring won't be applied at places where Alpha is 0..

 

Sorry, I misunderstood the problem.

 

You can move the Pixel object's alpha to a Mask and then blur only the blue channel of the object:

1. Copy the Pixel object's alpha to a Mask above it.

2. Fill the Pixel object's alpha to make it completely opaque.

3. Disable editing of all Composite channels except Blue.

4. Blur the Pixel object.

5. Restore editing of all Composite channels.

 

Do not merge the Mask back into the blurred Pixel object. The Mask needs to be at the top of the layer stack when exporting the result to an image file, to ensure intact RGB values in the export.