How do you create an alpha channel?

[Gianni_Maselli]

Hi,

As far as I understand PL allows you to create a selection with several tools and to transform it in a temporary mask for editing with the specific brush. At this point you can transform, assign it to a layer mask for a long time storage. It's also possible to create a selection via the 'Change Channels' dialog, even importing a previously made grey picture (from file to mask) to translate in a layer mask after having it been loaded. Finally I've noticed that you can create a layer mask from an alpha (I suppose) channel.

What I can't figure out is how to create a new, empty alpha channel, to paint in black and white, or how from a selection rather than a layer mask. I mean: In the Channels palette there is a button to load a hole channel as a selection and a second one to load it as a layer but no way to add a new (alpha) channel to fill, for example, with the active selection or with the clipboard content.

Is there a work around?

Thank you very much, Gianni

[Hoogo]

The meaning of Alpha Channel is different between PS and PL.
An "Alpha Channel" in PS is a way to store a grayscale picture for any purpose,
while in PL "Alpha Channel" is the transparency channel.

So what sort of "Alpha Channel" are you looking for?
If you're looking for the PS Alpha, then think of a new layer instead of a channel and turn the layer off.
If you're looking for the PL Alpha, then enable transparency for that layer. You can't paint in black and white in it, you have to use the erase-tools or the delete-key with an active selection. Or use a layer mask instead.

What I can't figure out is how to create a new, empty alpha channel, to paint in black and white, or how from a selection rather than a layer mask. I mean: In the Channels palette there is a button to load a hole channel as a selection and a second one to load it as a layer but no way to add a new (alpha) channel to fill, for example, with the active selection or with the clipboard content.

I don't use channels very often. In fact it seems that I only use the channels to view only one of RGB. Use a normal layer or layer mask for these purposes. Ctrl+V or the delete-key with active lasso tool should do.

[Gianni_Maselli]

So, I can make a selection/mask with, for example, the lasso and then with the eraser (white) I add to the mask while with the eraser (black) I subtract from the mask. Once the mask is complete, the button 'Layer Mask' > 'Create from Mask' stores the active selection/mask to a layer mask and that's fine.

I just don't realize what the mask brush is for, since it always add to the mask no matter if white or black is selected as the foreground colour.

I also still need to experiment further with the transparency concept as intended in PhotoLine.

Thank You.

[bkh]

I just don't realize what the mask brush is for, since it always add to the mask no matter if white or black is selected as the foreground colour.

I think it's just a quick way of refining the mask — you don't have to switch on mask editing mode and don't have to choose background and foreground colours. To reverse the operation of the mask brush, just hold the Alt key.

I also still need to experiment further with the transparency concept as intended in PhotoLine.

Like Hoogo, I'd suggest to use layer masks instead of alpha channels in PL: you can easily display a layer mask as a greyscale layer (just turn on the eye symbol in the layer panel), you can easily modify it using the ordinary painting tools, and you can have more than one of them. (And you can turn a layer mask into an alpha channel if needed.)

Regardless of how you create transparency in PL, there will be an appropriate alpha channel if you export to a format which supports transparency (e.g. TIFF, PNG, …)

Cheers

Burkhard.

[Gianni_Maselli]

To reverse the operation of the mask brush, just hold the Alt key.

Great, Thanks.

I like to use the mask editing mode because it's a visual help. The Keyboard shortcut is okay but for consistency (with the mask theory too) I'd also make the mask brush behavior to change in accordance with the foreground colour.

Anyway I think now I understand...

To create a new, empty alpha channel it's enough to click the Edit Mask button and a new channel is added to the channels list. To reverse the brush effect just select one of the two buttons in the Tool Settings dialog that appear when Mask Brush is selected: The brush or the eraser one.

The alpha channel is retained even exiting the edit mask mode; it only disappear to show up again as soon as this mode is re enabled. Provided you do not deselect anything, otherwise you loose the alpha channel for ever. I avoid this by moving the alpha channel to a layer mask: Channel to selection.

In any case the alpha is preserved in pld files only. As far as I know, neither TIF nor PSD retain the alpha channel.

Bye, Gianni

[Hoogo]

To create a new, empty alpha channel it's enough to click the Edit Mask button and a new channel is added to the channels list.

Wow, I never noticed that! But I guess this is more a side-effect with some technical background but the usual alpha channel. I would still prefer to call this channel simply mask.

I avoid this by moving the alpha channel to a layer mask: Channel to selection.

Same here: Better say "...moving the mask to a layer mask"

In any case the alpha is preserved in pld files only. As far as I know, not in TIF or PSD.

The mask is only preserved in PLD.
Originally alpha channel and transparency channel were 2 words for the same thing. Just enable transparency and store your mask there, or use a layer mask. This transparency can be saved as Tiff or any other file format that supports transparency.
All layers above background usually have their transparency enabled by default.

[Herbert123]

Here is my solution to save selections for later use in the same document while keeping them out of harms way, and keep the layer stack nicely organized:

1) convert the image to work in document mode (attributes-->document panel)
2) open the view panel, and switch to pages
3) create your mask/alpha channel any way you like
4) if not already a layer, convert this mask/alpha channel to a layer
5) add a new page in the pages panel
6) cut the mask layer in the main file page, and paste into the new page. Optional: group this mask into a grouped layer if you plan to build up a mask out of multiple parts and adjustment layers.
7) create a virtual layer of this mask (I use the grouped layer), and cut/copy it back into your first (main) page.

Now I can create a repository of different masks, combine them, hide them quickly, and so on, while it will automatically affect the virtual version I use in the main file. And the masks are out of the way. All non-destructive, if you want: apply any adjustment layer to these, and so on. These will save with this document only.

Of course, you could organize all your masks in a main group with sub groups at the bottom of the layer stack too, with a rectangle vector layer to separate those from the top visible layers.

Another option is to save your masks as a pattern - though less usefull, they will be available whenever you need them.
When working with separate mask files, the Documents tab in the view panel can come in very handy as well.

[Gianni_Maselli]

It's also possible to save the layer containing the mask by removing or switching off the background image (rather than all the layers below) in the latter case flattering the stack for saving a file containing the mask only. Then, with 'Tools > Change Channels' to load this mask as an alpha channel: Source = File - Destination = Mask (Gray Picture). You activate the edit mask mode and the alpha channel will appear in the channels list ready for you to be used.

One thing is for sure: PhotoLine is a powerful software it's a pleasure to discover.

Bye, Gianni.

[Hoogo]

Well, I really wonder why you like that channel so much? What is your goal? Is there any PS tutorial you want to follow in PL or something like that?

[Gianni_Maselli]

Well, I really wonder why you like that channel so much? What is your goal? Is there any PS tutorial you want to follow in PL or something like that?

Sometimes to isolate a subject from its background is a long work I don't even like at the first attempt. So, saving a mask it's necessary.

I was used to PS and thus I tend to search its workflow in PL. This is wrong, I know . It's just a matter of time, the time to get confident:-)

Bye, Gianni.

[SCX]

You can try to use a simple white layer, then use the brush-tool and fill it with active selection with 100% black and turn the layer invisible while working on the image. You can easily create a selection later out of this layer again.

[Gianni_Maselli]

You can try to use a simple white layer, then use the brush-tool and fill it with active selection with 100% black and turn the layer invisible while working on the image. You can easily create a selection later out of this layer again.

I'm not sure to have understood what you mean for filling a brush with a 100% black active selection.

I can paint in black a white layer over the background image but I don't have any feedback* until I transform it in a layer mask with 'Convert for Previous' in which case the painted layer becomes a grey (gray in US and PL) layer.

The concept stays the same even if applied in different ways...

Bye.

* Unless I set the blending mode to to 'lighten'

[SCX]

I thought, creating an alpha channel in PS means to save a selection. If you paint with 100% black on a white layer, you will have the selection on this layer.

Later on, you can restore the selection out of this layer with the tool "Farbkanäle tauschen" which should be somewhat like "Swap Colorchannels" or however this is translated in the English version of PhotoLine, or with the new feature "shift + left mouseclick."

[bkh]

Sometimes to isolate a subject from its background is a long work I don't even like at the first attempt. So, saving a mask it's necessary.

As I wrote before, I normally use layer masks to store a selection (mask in PL's lingo). I simply use Layer -> Layer Mask -> Create from Mask (or the corresponding item from the mask menu in the layer panel) to convert the mask into the layer mask. You can disable the layer mask by choosing "invisible" in the context menu of the "scissors" in the layer mask. Use Layer -> Layer Mask -> Apply to Mask (also in the mask menu in the layer panel) to get the mask (selection) back — or shift-click on the icon in the layer panel.

Cheers

Burkhard.