Transform in Properties Panel

[MahaB82A]

What does Transform in Properties panel mean? Because pixel in transform panel does not match with pixel in Image size. 

    

[Omar.Fathy]

The transform attributes in the properties panel are the attributes of the selected layer but the attributes in the Image Size window are the dimensions of the canvas size (the full working area).
You can use the transform attributes in the properties panel to edit the layer instead of useing Edit> Free transform for example.

[MahaB82A]

What you say is whether it is Image Size or Canvas Size, it is same. What is purpose of having separate tools for these two? 

[Omar.Fathy]

No, the Image size and Canvas size have different usage.
Canvas size increases or decreases the workable area, while image size increases or decreases the actual size of the image opened in the program.
Canvas size increase or decrease the size without scaling layers or design. Image size scale up or down the whole design and layers when you change the size. 
We use Canvas Size when we need to add an additional size to the design without affecting the layers and images in it. Or to cut a part of the design without scaling images down.

[Conrad_C]

No, this is not about Image Size vs. Canvas Size. Omar is talking about layer dimensions vs document dimensions.

In your original screen shot MahaB82A, Image Size is the pixel dimensions of the entire image: 2048 x 2048 px, and your Transform properties are for the selected layer only. In other words, if you were to choose Edit > Free Transform, the dimensions of the bounding box for the layer content would be 1792 x 1280 px. So there is no conflict, the Properties panel is measuring something different than Image Size.

Another way of proving this is that the Properties panel can show both:

• If you select a layer, Properties Transform shows you the pixel dimensions of the selected layer content (non-transparent pixels). 
• If you make sure no layers are selected (e.g., Select > Deselect Layers), now Properties Transform shows you the pixel dimensions of the entire document, now matching Image Size.

Image Size vs Canvas Size is a different subject:

• Image Size lets you change the dimensions of the existing canvas (scaling), and gives you the Resample option. 
• Canvas Size lets you add to or remove pixels from the existing canvas (expanding or trimming), without resampling. 

[Omar.Fathy]

Sure, In my main reply I mentioned canvas just to express the work area. 🙂 It is a common name in different softwares 🙂

[MahaB82A]

Why does this show same pixels?

 

[Conrad_C]

Image Size and Canvas Size always show the same number of pixels when first opened, because no changes have been made. At this time, the Image Size and Canvas Size are both reporting 2048 x 2048 pixels, which is true, that is what they are.

The difference between Image Size and Canvas Size is what kind of change you can apply to the pixel dimensions. For example, when starting from an image of 2048 x 2048 pixels as shown in your picture, entering 4096 x 4096 pixels in Image Size always produces a very different change compared to entering 4096 x 4096 pixels in Canvas Size. I already described how the two results are different in the earlier reply.

[Omar.Fathy]

Yes, as @Conrad_C said, because it is the document size and both of commands work on the document sizein different ways as I mentioened before.