Photoshop canvas size?

[sitnet]

Hey everyone I am using Photoshop CS4 and I have a question about it.

Is there a way to select a certain part of the actuall canvas (not the background, the grid pattern canvas that is invisible if you save the image) and remove it. I know you can go to Image>Canvas size but then you have to guess how large it is going to come out.

I know you can also crop but that doesn't work so well if your image is round.

So what I really want to know, does the canvas have to be rectangular and can you maipulate it manually, like you can erase and cut a background. Like free-transform the canvas?

Thank you!

 

[plazma]

No.

 

[d0b33]

you can use the pentool to draw around the part you want, or lasso tool, then copy paste on new layer or new canvas.

Edit:
Ok I see what you're saying, then no.

 

[Fudzy]

Images always have to be a square/rectangle although what you can do is if you use a format like PNG or GIF (PNG is much better) you can have transparent backgrounds which if lets say you wanted a circle, you could create a layer with just a circle in it then delete the background layer. Then goto Save image for web (Ctrl-Alt-Shift S) and save it as either a PNG or GIF. The image would still be confined to a square or rectangle but only the circle would be visible.

 

[sitnet]

OK thanks for the replies, I understand now