How to Change (Only) the Canvas Size in Mac Preview

How to Change Canvas Size in Mac Preview without Changing the Image Size

Want to add something to an image’s right (left, top or bottom) edge? Making a collage? Find out here how to change the canvas size for an image in Preview on a Mac without scaling the image itself.

First, Four French Felines

The number four in French (quatre) sloppily said, heard or written comes perilously close in English to being a cat or a kitten.

Quatre (spelled “cater” in its anglicized version) was, quite naturally, also at one time the term used for a die’s side with four dots. Not quite so naturally, those four dots came to mean, the story goes, to place diagonally (in lieu of the sides with two, three or maybe five dots, which do hint at some diagonal action if you ask me).

Either way, from cater-corner, it was not too far a stretch to today’s catty-corner and kitty-corner.

Speaking of corners… how about we kitty-corner a canvas and push out all its four sides without scaling the image content? Here’s how:

How to Change Canvas Size in Mac Preview without Changing the Image Size

Time needed: 2 minutes

To increase the size of an image’s canvas without scaling the image (with the result of empty space around the image) in Preview on a Mac:

  1. Open the image in Preview on the Mac.

    Backup: Press Command Shift S after opening the image to create a duplicate to work on in Preview if you want to preserve the original image.
    Images only: Expanding the canvas works for image formats in Preview; you cannot expand the canvas for PDF documents.

  2. Press Command A.

    Here’s why: This will select the current image as is.
    Menu alternative: You can also choose Edit | Select All in the Preview menu.
    Select all the image to start expanding its canvas in Preview

  3. Now press Command X.

    Here’s why: With this command, you cut the current selection—i.e., the whole image as is—from the canvas and move it to the macOS clipboard for later pasting.
    In the menu: Using the menu, pick Edit | Cut.
    Convert to PNG: if you cut from a JPEG or other image without translucency, click Convert under Convert this document to PNG?; to expand the canvas, Preview needs to add transparency in the expanded areas.
    Convert an image to PNG to expand its canvas with translucency

  4. Select Tools | Adjust Size… from the menu.

    No cropping: Note that you can only crop inside the existing canvas in Preview, not outside it to expand the image area.

  5. Choose the size you want to use for the canvas.

    Pixel precision: Select pixels for Width: and Height:, then enter the adjusted size in pixels.
    Other sizes: You can also choose percent, of course, and scale the canvas size.
    Independence declaration: To choose a proportion different from the original canvas, turn off Scale proportionally.

  6. Click OK.

    Choose the new size for the image canvas

  7. Press Command V.

    Here’s why: This will paste the image you cut to the system clipboard in its original size.
    Paste and position the original image in the expanded canvas

  8. Use the mouse cursor to position the pasted picture in the newly expanded canvas.

  9. Add further image elements, as desired, beyond the original image’s constraints.

    Add new elements beyond the original image borders on the expanded canvas in Preview

  10. Save the image in the desired format.

    No translucency: If you save the image in a format without translucency (such as JPEG), the background will be filled in with black.

As an alternative, you can also paste the image onto a larger, empty image that has the desired size, of course.

How to Change Canvas Size in Mac Preview without Changing the Image Size: FAQ

The image will not paste into the resized canvas; what can I do?

Chances are, something replaced the image in the clipboard since you cut it from the original canvas.

To start over, press Command Z to undo until the image is back in the original canvas, then resume with the steps above.

(How to change the canvas size in Mac Preview without changing the image size tested with macOS Sonoma 14.3; first published May 2024)

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