So in many applications, you can strech the entire raster image by changing the image size.
So say it's 100x100 px, and you have a picture of an A on it
When you change it to 100x120 px, you will then have a stretched A
Change canvas size has a selection of 9 buttons specifying where to put the original image, then increases picture size, without stretching the image. So if you click the top middle button, you will then get your extra 20 pixels added to the bottom with no deformation of the art on the rest.
This is FANTASTIC in UI work when something is one or two pixels off, or you're decomposing one image into many.
So say it's 100x100 px, and you have a picture of an A on it
When you change it to 100x120 px, you will then have a stretched A
Change canvas size has a selection of 9 buttons specifying where to put the original image, then increases picture size, without stretching the image. So if you click the top middle button, you will then get your extra 20 pixels added to the bottom with no deformation of the art on the rest.
This is FANTASTIC in UI work when something is one or two pixels off, or you're decomposing one image into many.