What exactly does the size of a layer mean?

[SEASONS283724216wp2]

Why do we say resizing a content on a layer by using the Free Transform tool is called resizing the layer?

For example, if I draw a rectangle on an empty layer and resize it within the canvas size, does that change the size of the layer itself?

Is resizing a layer's components the same as resizing the layer? Doesn't the layer itself have a size?

The contents of a layer may exist outside the canvas size, in which case the size of the layer is larger than the canvas, isn't it?

What exactly does the size of a layer mean?

[Semaphoric]

I've always understood it to be the box that contains the non-transparent pixels, like what you see when the Layers Panel Options is set to Layer Bounds for the thumbnail.

[Stephen_A_Marsh]

There are different layer kinds. For a "standard" new empty artLayer - there is no size until there is content, it's just blank to the canvas size... And yes, a layer can have content that is beyond the visible canvas.

[SEASONS283724216wp2]

"there is no size until there is content, it's just blank to the canvas size."

Does this mean that a layer with no content has no size, and that the size of a layer with content is the size of the content? For example, if I draw a shape smaller than the size of the canvas on an empty layer, does it mean that the size of the layer is the size of the shape?

[Stephen_A_Marsh]

From a scripting perspective, yes.

https://gist.github.com/MarshySwamp/ef345ef3dec60a843465347ee6fcae2f

https://prepression.blogspot.com/2017/11/downloading-and-installing-adobe-scripts.html

[Conrad_C]

I understand the pixel dimensions of a layer to be the smallest rectangle that encloses the most extreme non-transparent pixels of a layer. In non-math terms, it’s the size of the rectangle you see when you make the transform bounding box visible, by choosing Edit > Free Transform or enabling Show Transform Controls in the options bar when the Move tool is selected. If there are non-transparent pixels outside the canvas, the transform bounding box does enclose those.

The pixel dimensions of each layer have a direct effect on the document file size. Uniform areas of a pixel layer are very easy to compress. So if you have two documents of the same pixel dimensions and number of layers, where the layers in the first document don’t fill the canvas (they have smaller pixel dimensions than the document), and the same number of layers in the second document are fully painted from edge to edge, the second document will have a much larger file size.

[SEASONS283724216wp2]

I can understand what you're saying.  As a beginner, I'm wondering that if the layer is a transparent glass plate, then the glass plate itself has a size(although it's only visible on the screen within the canvas size), and the size of the content displayed on the glass plate is a separate thing.

[Stephen_A_Marsh]

A glass plate has a physical size, a blank artLayer doesn't... A blank artLayer is like the universe, it's infinite (well, it's almost infinite, there is a maximum canvas size of 300,000 x 300,000 px for PSB or 30,000 for many other formats)! So the artLayer has no size however it is bounded by the canvas. I have not tried to move layer content outside of the canvas limit though!

[Conrad_C]

I can understand what you're saying.  As a beginner, I'm wondering that if the layer is a transparent glass plate, then the glass plate itself has a size(although it's only visible on the screen within the canvas size), and the size of the content displayed on the glass plate is a separate thing.

By @SEASONS283724216wp2

That’s close to an analogy that’s been used in the past for layers, that layers are like the transparent cels used in traditional film animation, which were stacked. Each film cel had a different element of the frame. The cel has a size, but only a small part of each cel might be painted. In Photoshop, the size of a layer is measured by the size of the painted area.

The animation below shows what I explained in my earlier reply, because Photoshop provides tools for this. In the Info panel you can see that I have enabled displaying the pixel dimensions of the entire document, which in this example are 2100 px by 1500 px. That number stays constant, but as I change each layer and choose Edit > Free Transform, the numbers that do change are the pixel dimensions of the selected layer, shown in both the options bar for the Move tool at the top of the workspace, and also in the Info panel.

So three different sets of values are shown:

The pixel dimensions of the document

The pixel dimensions of Layer 1

The pixel dimensions of Layer 2

[SEASONS283724216wp2]

Thanks for the detailed answer. "In Photoshop, the size of a layer is measured by the size of the painted area."

I had (mis)understood that a layer is a transparent glass plate and has its own size, and although the layer visible on screen is limited to the size of the canvas, the maximum size of a layer is 300,000px x300,000 (PSB).

So it didn't make sense to me to describe the size of the contents of a layer as the size of the layer. I'm familiar with the method you showed for checking layer size, I was just wondering why it was called "layer size".

[Stephen_A_Marsh]

I was just wondering why it was called "layer size".

By @SEASONS283724216wp2

Because layer content size adds an extra word.

[SEASONS283724216wp2]

I'm sorry, but can I ask one more question? In the example above, if I select <layer2> and move the layer with the move tool, am I moving the object(or image) or the layer itself?

[Stephen_A_Marsh]

The object, there is no layer :]

[Conrad_C]

I'm sorry, but can I ask one more question? In the example above, if I select <layer2> and move the layer with the move tool, am I moving the object(or image) or the layer itself?

By @SEASONS283724216wp2

If you simply selected a layer in the Layers panel and then selected the Move tool, then dragging moves all non-transparent pixels on that layer (it’s safe to phrase that as “it moves the entire layer”).

If you selected a layer, and then you used a selection tool (such as the Object Selection tool or a marquee selection tool such as the Lasso tool) to select a region of pixels on the layer, then dragging the Move tool drags only the selected pixels, and the rest of the pixels on the layer remain where they are.

So keep that in mind, that there are two levels of selection: The entire layer, or any region(s) of pixels on the layer. Those two levels of selection are what let you transform (move, rotate, scale, skew) or delete an entire layer, or only selected region(s) of pixels on the layer, your choice depending on what you need to do.