The image canvas is the work area of the image and defines the image’s dimensions—for example, 200 by 300 pixels. Sometimes you need more canvas to add elements to an image; other times you want to make the canvas size smaller.
Note: Reducing the canvas size is not always the same as cropping an image. For images with layers, reducing the canvas size does not delete the pixels outside the new canvas area, it just shows less of the layer. Background layer information will always be deleted, even when there are other layers in the image.
Other resize options: You can also change the image size by resizing, cropping, or printing at a different size. For a comparison of these options, see Other ways to change an image’s size.
To change the image’s canvas size:
Choose Image > Canvas Size to open the Canvas Size dialog.
Choose settings from the New Dimensions group box:
Width, Height Enter values for the new canvas size.
Units Use this drop-down list to change the measurement system.
Lock aspect ratio Mark this check box to constrain the new canvas size to the current image proportions. The numeric edit control (below the check box) indicates the image’s current width-to-height ratio. Change this value to create a different aspect ratio.
Background Click in the color box and pick a color for any added canvas. Or, mark the Transparent check box to have any added canvas be transparent. Right-click the color box to pick from the Recent Colors dialog. Note: You must choose a color for any canvas added to the background layer.
Set the placement of the image in the new canvas. In the Placement group box, click a placement button. The fields to the right of the placement buttons will show the amount of canvas added or subtracted from each edge.
Note: You can also enter values in the fields to control image placement.
Click OK.
Scaling and Transforming Images