How to Edit the Alpha Channel

[John-B]

New to AP,  trying to figure out how to edit the alpha channel of a TIFF file. In the Channels panel, I click Composite Alpha to make the alpha channel editable, but some tools seem to work inconsistently or not at all in the alpha channel. For example, I can select all and Fill the alpha channel with white, but not with black or gray. Same with the Paint Brush tool. And it won't let me paste into the channel, pasting with the alpha channel editable and the other channels set to non-editable, the pasted image does not go into the alpha channel. If I do fill the alpha channel with black (I don't remember how I did it once), the image disappears and and I can no longer see it. Is there a way to edit the alpha channel as with a normal layer - using fill, brush, paste, etc.? Is there a way to edit the alpha channel and still see the entire image? Better yet, is there a setting to always see the entire image, regardless of the alpha channel (Transparent Background doesn't do it)?

[Lee D]

Hi John-B,

We have some online videos on channels available, I've listed them below.

• Channels
• Channels for Alpha Masking
• Channels: Creating/Storing Selections
• Editing Single Channels
• Channels: Greyscale Blending
• Channel Packing

[John-B]

4 hours ago, Lee D said:

Hi John-B,

We have some online videos on channels available, I've listed them below.

• Channels
• Channels for Alpha Masking
• Channels: Creating/Storing Selections
• Editing Single Channels
• Channels: Greyscale Blending
• Channel Packing

Thanks. I've looked at all those videos and cannot find answers to my questions. I already watched most of them before posting my question. I don't want to create a mask or a selection, or save a selection, or edit an RGB channel (non-alpha channels seem to work normally), or channel packing (not even sure what that is). I'm just trying to edit the alpha channel as if it were a regular grayscale layer and, as I said, I've not been able to figure out how to do it. I'm creating transparent/cutout TIFFs for use as textures for 3D models. 

If there is a particular place in one of those videos that shows how to use the Fill or Paintbrush tool with a color other than white in an alpha channel, please point me to it. Or how to paste a grayscale image into an alpha channel, for example from another non-alpha layer or image. Or how to see an entire image when parts of the alpha channel are black. I don't want to just create an alpha channel from a selection. If there are tutorials that address these questions, I've not found them yet.

I'm sorry if these are stupid questions. I'm trying to learn AP after many years of using Photoshop, and some things don't seem to translate. In PS, you just select the alpha channel, and everything, all the tools, work just as they do with the other channels/layers. In AP, that doesn't seem to be the case, so I must be missing something very basic since all I can do with alpha channels is make selections and fill them with white.

[lepr]

.

[R C-R]

17 hours ago, >|< said:

I hear what you're saying about not wanting to edit a mask, but that's the solution to your problem until Affinity re-engineers its restrictive channels functionality.

Among other things, I don't understand why the Composite Alpha channel has a 'visible' button since unless I missed something that makes everything invisible. Why would you need or want to do that? 

[Gnobelix]

18 hours ago, >|< said:

 If that's of interest to you, I can provide more detailed instructions. 

Hello @>|<,

Please a detailed instructions.
I would be happy

 

Cheers

[John-B]

On 1/16/2019 at 4:42 PM, >|< said:

I hear what you're saying about not wanting to edit a mask, but that's the solution to your problem until Affinity re-engineers its restrictive channels functionality. Copy the pixel layer's alpha to a mask, make the pixel layer opaque, paint in the mask as if it was a greyscale pixel layer, and then optionally merge the mask back into the pixel layer's alpha. If that's of interest to you, I can provide more detailed instructions.

 

Yes, please post detailed instructions. You mentioned merging with the alpha channel; that would work the same as pasting if I can create/edit my alpha channel in a grayscale layer. Thanks. 

I guess I'm not missing anything, editing the alpha channel directly is not supported. I mostly need a program like this to create textures for 3D models and UI graphics, so working with alpha channels is a big part of what I do.

[lepr]

.

[John-B]

On 1/23/2019 at 4:49 PM, >|< said:

1. Open the  image file into AP so you have a Pixel object named "Background".

2. If "Background" is completely opaque, then simply add a Mask Layer and then go to step 5.

3. In Channels panel, right-click the thumbnail of "Background Alpha" and pick Create Mask Layer to copy the alpha into a mask.

4. Again right-click the thumbnail of "Background Alpha" and pick Fill this time so only the mask is controlling opacity.

5. Edit the mask with a paint brush, a smudge brush, a clone brush or various other tools. Option-click the mask thumbnail if you want to view the mask as a greyscale layer (click any other layer to restore the normal view of the document) while you edit it.

6. Flatten the document to merge the mask into the alpha of "Background" or simply export to a flat file format.

 

As the attached screen capture shows, I got through step 4, I created the mask and filled it. That does let me see the entire image, but I still can't edit the alpha mask. This is a transparent UI panel that I need to enlarge. In the screen capture, I've resized the image, and now I need to make the gray part of the Alpha channel fill the image, but keep the rounded corners the same. Anything I try to do — copy/paste, select/drag, fill — only affects the image layers, not the alpha channel. If I try to sample the gray color with the eye dropper tool, I get the color in the image. This happens when the pencil icon is dimmed for all but the Composite Alpha channel. Am I missing something? Editing the alpha channel should be simple and straightforward.

 

[lepr]

.

[John-B]

19 hours ago, >|< said:

You've filled the mask (made it completely "white") and that is not what I said to do. I said to fill the channel named "Background Alpha".

 

There is no "Background Alpha" channel after Create Layer Mask. The attached shows the Channels panel before and after your step 3. See the attached screen capture, before step 3 on the left, and after on the right. There are only Composite Alpha and Mask Alpha channels. 

[lepr]

.

[John-B]

On 2/14/2019 at 10:36 AM, >|< said:

That's because the mask is the active layer at that moment. Select the layer named Background to access its channels including Background Alpha.

 

Thanks for all your help, but I'm just not getting this at all. I've tried MANY times, and just cannot seem to get it to work. Every time, I end up spending way too much time, getting frustrated, then giving up and using someone's else's computer with Photoshop, and getting it finished in a few minutes. Most recently, I tried to create a new TIFF with an alpha channel (a black rectangle with a gray alpha), and failed at that.

I don't understand why doing anything with an alpha channel, which is treated just like any other layer in Photoshop, is so difficult in AF. The functionality to edit a grayscale channel already exists in the program. There's even a Pencil icon for the alpha channel which the hint says makes it editable, but doesn't. Access to the alpha channel seems like basic functionality for a program such as this.

[DeepShader]

+1

[John-B]

On 1/23/2019 at 4:49 PM, >|< said:

Option-click the mask thumbnail if you want to view the mask

I finally got it working. Thanks again. I discovered I'd missed this one critical step. If you don't opt-click the thumbnail (obviously), the mask is invisible, and it looks like nothing is happening.

One more thing I still can't seem to do is paste into the mask. For example, if I want to copy an alpha channel from one image to another.

[lepr]

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[.eb]

this is mind numbingly stoopud.

[Old Bruce]

On 3/4/2019 at 2:32 PM, John-B said:

One more thing I still can't seem to do is paste into the mask. For example, if I want to copy an alpha channel from one image to another.

Very convoluted method follows.

Doc A has the Alpha Channel you want to copy and paste into Doc B. Open both. 

Doc A select the Alpha Channel you want to copy & paste, make a new grayscale layer from the control click menu. Copy that Greyscale layer.

In Doc B paste the greyscale layer and hide everything else. Invert the layer, make a spare channel from any channel and that can then be loaded into the Doc B Alpha Channel.

[SLowmo75]

I still don't get it. At all. Alpha's in AP have been a complete mystery to me since day one.

In PS you can edit  alphas just like any other layer and it's as simple as it sounds.

in AP there are all kinds of edit and visibility buttons that either appear to do nothing or do what you least expect them to, and menu options that I simply, try as I might, do not understand. At all.

I've tonight resorted to simply saving a separate black and white image out and calling that my alpha. Does the job. Totally not what you want for a game engine, but I don't need that any more, I just need a black and white image, and don't really mind that it's not embedded as an alpha...

... although that would be very nice!

[Helmar]

@MEB  Can you perhaps tell me what is the best way to turn a luminosity layer into an alpha mask?

[MEB]

Hi Helmar,
If you meant a greyscale layer, go to menu Layer > Rasterise To Mask.

[efflam]

Is there any way to get the developer's attention on this? The current workflow makes affinity photo unusable for any texture work in games involving alphas. Especially for Unity where you routinely have to copy roughness into the alpha channel of the metallic map.
I hate photoshop but this is a deal breaker for me. Give us the ability to copy paste buffer into alpha.

[tazcebula]

This is a massive issue, so much so that I'm going back to Photoshop - sorry I can't wait for you guys to sort it out, why on earth can you not edit alpha channels - it makes no sense at all.  This is a basic requirement for game dev.

Edited September 27, 2019 by tazcebula@gmail.com

[Patrick Connor]

@efflam & @tazcebula

Welcome to the Serif Affinity forums  

39 minutes ago, tazcebula@gmail.com said:

This is a basic requirement for game dev.

Agreed, but that has not been our target market so far, sorry. Better tools to edit the alpha channel directly will be needed before Affinity Photo would be more suitable for the parts of the games industry that reply on TGA-alpha for texture storage. I would not say it "makes no sense at all", it's just not right for your particular use.

[tazcebula]

54 minutes ago, Patrick Connor said:

@efflam & @tazcebula

Welcome to the Serif Affinity forums  

Agreed, but that has not been our target market so far, sorry. Better tools to edit the alpha channel directly will be needed before Affinity Photo would be more suitable for the parts of the games industry that reply on TGA-alpha for texture storage. I would not say it "makes no sense at all", it's just not right for your particular use.

You know I don't agree with that and I stick by what I said - it makes no sense at all, I was actually pointing out that it was a problem for game dev, but its a problem for anyone who wishes to use transparency, especially any kind of developer and currently the way it works in Affinity Photo is an absolute joke to be honest. I'm a developer and I'm surprised how badly it has been implemented especially considering how easy it would be to implement. At this stage I'm not sure what the point of the alpha channel is, and sorry if I come across as being harsh, but it is pretty useless currently and if there is some magical way of putting it to use, it is in dire need of UAT, alpha channels are an industry standard its got nothing to do with our particular use case at all.

Edited September 27, 2019 by tazcebula
bad grammer