Default color for a new correction layer or a mask is not white anymore

[smadell]

Here's the simplest way I can think of to understand the difference between Select All and Selection from Layer.

(1) Create a new document and add a single, blank pixel layer.  (2) Fill that layer with any color you want.  (3) Now, use the Eraser tool to erase some of the pixels.

If you look at the Channels panel, you should see that the Alpha channel for that layer is white in all areas that contain color, but is black where you erased.

Now, choose Select All. You should see that the entire layer has been selected. Deselect and instead choose Selection From Layer. Now, you should see that your selection includes ONLY the pixels that remain colored, but the areas where you erased are not selected.

My interpretation is simply this:  Select All will select all the pixels, without regard to the Alpha Channel for that layer. Selection From Layer, on the other hand, takes the layer's Alpha channel into account, and will not select transparent pixels.

[R C-R]

12 minutes ago, smadell said:

When you do a Selection From Layer (although not when you do a Select All) you select all the pixels, but then use the Alpha Channel to determine how much they are selected.

To be honest about it, I am still having problems understanding how a pixel can be anything other than fully selected or fully unselected. I get that the marching ants path only shows pixels where the path encloses at least 50% of a document pixel, but that does not seem to me to be the same as selecting only part of those pixels.

[smadell]

To say that the pixel is "partially" selected does not (I don't think) mean to imply that a percentage of that pixel's size is selected. It means, in some sense, that the selection is only fractionally active.

I have always thought of "selections" as if they were temporary Spare Channels, in the sense that some pixels are "on" and some are "off". The "on" pixels are the ones on which a subsequent action would be undertaken. For instance, if I use the Marquee tool to select some of my pixels and then Copy them, it is only the selected pixels (the "on" pixels) that are copied.

I understand the opacity of a layer to be the degree to which it occludes the layer beneath it. So, a layer that is set to 50% opacity will only partially occlude the layer underneath it.

Partial selection of pixels is some hybrid of segregating pixels into "on" and "off" pixels, and combining that with a concept similar to opacity in the sense that an "on" pixel might only be "partially on." It is like having a dimmer switch for individual parts of the selection.

A perfect example of this is a Luminosity Mask. In Affinity Photo, the simplest way to make a luminosity mask is to Command-Option-Click on a layer icon. This results in a selection, but a subsequent mask is not all white or all black, nor is it white in selected areas and black in unselected areas; it is shades of grey. This is because the Command-Option-Click thing caused a "partial selection" of all pixels based on their luminosity.

[R C-R]

28 minutes ago, smadell said:

To say that the pixel is "partially" selected does not (I don't think) mean to imply that a percentage of that pixel's size is selected. It means, in some sense, that the selection is only fractionally active.

I think of it not as 'fractionally active' but instead as just determining to what extent something will be applied to the pixel. I don't know if that is just a meaningless semantic difference or what, but it seems easier to wrap my head around than that somehow only part of a pixel can be selected.

[smadell]

You say tomato, I say tomato. (That sounds better out loud, though, doesn’t it?) I think we’re saying effectively the same thing here. I think what this thread has shown me is that I need to do some more reading on alpha channels, since I’m pretty sure that’s where the salient information is.

[walt.farrell]

1 hour ago, R C-R said:

I think of it not as 'fractionally active' but instead as just determining to what extent something will be applied to the pixel. I don't know if that is just a meaningless semantic difference or what, but it seems easier to wrap my head around than that somehow only part of a pixel can be selected.

I don't think anyone has mentioned feathering of selections yet, but it seems quite relevant/related, to me. You have pixels outside of the marching ants that are fractionally affected.

Also consider:

1. Activate the Rectangular Marquee Selection Tool
2. Set Feathering to 500px.
3. Make a selection that is 300 x 300 px
4. Where are the marching ants?

[R C-R]

2 hours ago, walt.farrell said:

I don't think anyone has mentioned feathering of selections yet, but it seems quite relevant/related, to me. You have pixels outside of the marching ants that are fractionally affected.

But are the pixels actually outside the selection or only outside the pixels the marching ants show as selected?

[Ron P.]

5 hours ago, walt.farrell said:

Where are the marching ants?

They went home, got tired of being confused on when and when not to march. 😄

[walt.farrell]

7 hours ago, R C-R said:

But are the pixels actually outside the selection or only outside the pixels the marching ants show as selected?

For they simple case of feathering where the marching ants show, the usual explanation I remember seeing here is that the pixels outside the ants but within the feathering radius are "less than 50% selected". That doesn't really explain things, of course, and there does not seem to be an explanation of feathering in the Help.

But I believe it is all related to this discussion.

[R C-R]

4 hours ago, walt.farrell said:

For they simple case of feathering where the marching ants show, the usual explanation I remember seeing here is that the pixels outside the ants but within the feathering radius are "less than 50% selected". That doesn't really explain things, of course, and there does not seem to be an explanation of feathering in the Help.

I think a better explanation is more pixels are selected than the ants show as selected, but whatever is applied to the pixels not shown as selected won't be applied at full strength.

[Alfred]

45 minutes ago, R C-R said:

whatever is applied to the pixels not shown as selected won't be applied at full strength

Whatever is applied to the pixels which are selected but not shown as such won’t be applied at full strength. However, there will also be pixels which are shown as such but also won’t be subject to “full strength” application. The “marching ants” indicate the demarcation between those two regions.

[R C-R]

29 minutes ago, Alfred said:

Whatever is applied to the pixels which are selected but not shown as such won’t be applied at full strength. However, there will also be pixels which are shown as such but also won’t be subject to “full strength” application. The “marching ants” indicate the demarcation between those two regions.

I am not sure exactly what you mean about what the demarcation shows since there can be pixels in both regions that are not subject to  “full strength” application.

[Alfred]

2 hours ago, R C-R said:

I am not sure exactly what you mean about what the demarcation shows since there can be pixels in both regions that are not subject to  “full strength” application.

I just meant that the “won’t be applied at full strength” criterion doesn’t only apply to the “pixels not shown as selected” side of the demarcation line. As you’ve observed, there can be (and, in the case of feathering, will be) pixels on the other side of that line which are less than 100% selected and will consequently be subject to less than 100% application .

[smadell]

So, here's another video. I've tried to demonstrate a couple of things. (1) Select All and Selection from Layer work differently, in that only Selection from Layer takes the layer's alpha channel into account. (2) The selection is independent of any particular layer. Even when layers are hidden (or when none are active) the selection still exists. (3) A selection which has been created, and which remains active, can act on a different layer. (4) The "marching ants" exist at the point where pixels are selected 50% or more. In the video, note that the marching ants are present right down the middle of the canvas (since they were based on a linear gradient). (5) When an adjustment layer is created with an active selection that contains "partially selected" pixels, the adjustment layer's mask can be anything from white to black, and this is dependent on the degree of selection of the pixels when the adjustment was first created.

I know that was quite a mouthful. So, here's a video...

[R C-R]

6 hours ago, smadell said:

(4) The "marching ants" exist at the point where pixels are selected 50% or more.

Again, it is my understanding that pixels can be either selected or not selected, but they cannot be partially selected. So I am still not sure what "selected 50% or more" actually means.

[smadell]

From the Affinity Photo Help (online), in the section regarding "Pixel Selections from Layers":

"You can create pixel selections based on layers (or layer groups) or layer luminance.

"If the layer or layer group contains areas which have an opacity lower than 100%, these are partially selected. This partial selection is based on the percentage of their opacity (i.e. areas of 20% opacity will be selected by 20%). Transparent areas will not be included in the selection.

"A selection marquee only appears around areas which are selected by more than 50%. Areas selected by 50% or less will not display a marquee at their edges."

[R C-R]

2 minutes ago, smadell said:

"If the layer or layer group contains areas which have an opacity lower than 100%, these are partially selected. This partial selection is based on the percentage of their opacity (i.e. areas of 20% opacity will be selected by 20%). Transparent areas will not be included in the selection

Note that this does not say anything one way or the other about pixels being partially selected, just layers or layer groups.

[smadell]

The Help topic discusses “areas” of layers. If that’s not a clear reference to pixels, I’m not sure how else to convince you.

As is sometimes said about other, unrelated questions: “Some things are true, whether you believe in them or or not.”

[R C-R]

7 minutes ago, smadell said:

The Help topic discusses “areas” of layers. If that’s not a clear reference to pixels, I’m not sure how else to convince you.

So you are saying areas of layers & document pixels are effectively the same thing? If so, how do you reconcile that with selections being independent of any layer?

[smadell]

1) “Areas of a layer” seems to be a clear reference to pixels on that layer.

2) While selections exist independently of any particular layer, those selections will act on whatever layer is active.

[R C-R]

2 hours ago, smadell said:

1) “Areas of a layer” seems to be a clear reference to pixels on that layer.

2) While selections exist independently of any particular layer, those selections will act on whatever layer is active.

OK, but what can you do in Affinity that affects only part of a pixel? Shouldn't that be possible if you can select only part of a pixel?

[Alfred]

2 hours ago, R C-R said:

OK, but what can you do in Affinity that affects only part of a pixel? Shouldn't that be possible if you can select only part of a pixel?

When you feather the edges of a selection you’re not fully selecting parts of the edge pixels, you’re partially selecting whole edge pixels. To put it another way, instead of doing this

you’re doing this:

So when you subsequently do something that affects the selection you’re not fully affecting part of a pixel, you’re partially affecting a whole pixel.

[walt.farrell]

5 hours ago, Alfred said:

So when you subsequently do something that affects the selection you’re not fully affecting part of a pixel, you’re partially affecting a whole pixel.

OK, but if we consider the partially selected pixels in your bottom example, what can we do to the portions of those pixels that are inside the selection boundary, vs what happens to the portion outside it?

[Alfred]

22 minutes ago, walt.farrell said:

OK, but if we consider the partially selected pixels in your bottom example, what can we do to the portions of those pixels that are inside the selection boundary, vs what happens to the portion outside it?

As discussed earlier in this thread, whatever you apply to the selected pixels will only be fully applied to the fully selected pixels (the three in the middle in my example). For the partially selected edge pixels (the two at each end in my example) whatever you apply will be partially applied, depending on the degree of selectedness.

[Old Bruce]

Pixel layers are 1, 3 or four Grey scale channels. They go from black to white. The 100% selected pixel is one that will be showing at 100% opacity, 50% selected is 50% opaque and 10% selected is 10 percent opaque.