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previously, what I've asked is here. now, if it is assumed that there are no pixels and I am selecting no pixels but an area, why "lock transparent pixels" command from the layers panel for the selected layer, prevents painting the layer with brush tool etc. inside as well as outside the selection?

after filling the selected area with color the "image>trim" command trims the transparent pixels around it but if the selection is not filled then the output of the command doesn't show any difference.

another question arises after all this consideration : what is the difference among "empty area (in my words "empty pixels")","transparent pixels", "filled pixels"?

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  • Hi. Welcome to GDSE. As it stands, both this question and your other question read a bit like an XY Problem to be honest, and I think it would probably be better if you explained what you are actually trying to create.
    – Billy Kerr
    Commented Jan 3, 2021 at 11:24

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Lock transparent Pixels means.... don't allow transparency alteration to any pixel which has transparency.

Why you appear to think you should be able to then alter the transparency is a mystery to me. The lock transparency command could not be any more clear in my opinion. This command is helpful when you have partially transparent pixels and need to alter things like the hue, or luminosity of those pixels without changing the transparency - i.e. an RGBA pixel where you wish to alter RGB but retain the A. It is not a command to use if you want to alter 100% transparent pixels.

As for trimming.... if all that exists are transparent pixels and you choose the Trim command.. it would then trim the document to nothing - 0x0px. Therefore if everything is transparent and you attempt to trim by transparency, nothing happens because Photoshop doesn't support 0x0px documents. Every Photoshop document must be, at a minimum, 1x1px.

The difference between transparent pixels and filled pixels are pixels which have a hue or value are actually rendered and seen as filled, even if there's 99.9% transparency. Any amount of hue or value makes a pixel "filled".

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  • I want to clear my confusion about the transparent layer and pixels. when I create a document with "background content : transparent" it creates a transparent "layer 1" in the panel. now if I lock transparent pixels I maybe able to select some transparent pixels but can't paint them. I think this is a proof that transparent layer consists of transparent pixels. cause previously I get to know that transparent layer doesn't contain any pixels and this statement is confusing me. secondly, if I can select transparent pixels then why can't I move them as it is possible only for filled pixels
    – Morshed Sakib
    Commented Jan 3, 2021 at 4:32
  • No.. you can't "select" transparent pixels. I thought that was made clear in your other question. Just because you can draw "marching ants" does not mean the area is "selected".
    – Scott
    Commented Jan 3, 2021 at 8:53
  • I'l be frank... this is all something which no one I've ever encountered has struggled to grasp. If you are struggling this much... perhaps image editing merely isn't something you are going to find "easy" and therefore enjoyable. It's sort of like... if you can't grasp how an internal combustion engine uses gas to push pistons... being a mechanic would not be a wise choice for a career or hobby. 100% transparent pixels do not technically exist. Therefore they can't be selected or altered until they are not 100% transparent.
    – Scott
    Commented Jan 3, 2021 at 9:50
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I think the clarification you need is that an "empty area" or a transparent layer does not contain pixels. Therefore, trying to "Move" a selected "area" does nothing. There is nothing to move.

In this example I make a selection, move the selection, choose the Move Tool, and get the "the selected area is empty" warning. This is because I am working on the top layer which is empty. I then select the underlying layer with the blue rectangle and am then able to move it.

enter image description here

Selecting an "area" of a transparent layer allows you to color, paint, etc. just inside that selected area. The "Lock Transparent Pixels" command in the Layers Panel locks all transparent pixels in the Layer whether they are selected or not.

It is possible to color a selected "area" of a transparent layer (a Layer with nothing on it). Then you can change those pixels to 0% Opacity (in the layers panel) and be able to move that selection, increase their Opacity, and they will have moved along with the selection. In other words you can have pixels with no Opacity that appear transparent, but they are still pixels that can be moved- as opposed to an empty "area" that contains no pixels.

I don't really understand your question about Image>Trim but it makes perfect sense that if there is nothing to Trim then nothing will happen.

Without some context to what you are actually trying to create here, the question is very broad and it's purpose is vague.

A suggestion- It is important that you ask one question at a time. Otherwise it makes it difficult to answer. More importantly, it makes it very hard for others to search and benefit from a specific answer in the future.

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