Image Canvas Extender

Extend image canvas size in any direction with color fill or transparency.

Tested tool guide Tested browser tools Checked August 16, 2026

What Image Canvas Extender does, with a checked example

Image Canvas Extender enlarges the pixel bounds around an existing image while leaving the source content at its original scale. Specify space on the left, right, top, or bottom, then fill that newly exposed area with a selected color or transparency. Unequal amounts place the original off center, which is useful for labels or composition. The common surprise is that extending a canvas is not resizing or generative outpainting: the tool adds pixels around the image but does not stretch or reconstruct its subject.

Worked example

A concrete input and expected output from the current implementation.

Input

100 x 80 px source image; left 10 px; right 20 px; top 5 px; bottom 15 px; fill transparent

Expected output

130 x 100 px image; the source begins 10 px from the left and 5 px from the top; all added pixels are transparent

The width is 100 + 10 + 20 = 130 px, and the height is 80 + 5 + 15 = 100 px. The left and top additions determine where the unchanged source begins inside the larger canvas.

How the result is produced

Directional size calculation

The new width is the source width plus the left and right extensions. The new height is the source height plus the top and bottom extensions. Source pixels retain their dimensions and shift within the larger coordinate space by the left and top amounts. Corner regions outside the source are included in the newly added area.

Added-area fill

The selected fill applies only to pixels introduced by extending the canvas. A color fill gives those regions the chosen color, while transparent fill leaves them without visible color when composited. Transparency remains usable only in image formats that support an alpha channel. JPEG, for example, cannot preserve transparent pixels.

Good uses

Add transparent space above a product cutout so a headline can be placed there later without scaling the product.
Create a solid border with different widths on individual sides of an image.
Extend only the right side of a photograph to reserve blank space for captions or interface controls.

Limits and checks

Canvas extension does not synthesize scenery, continue textures, or intelligently fill missing background content.
Transparent padding still counts toward the image's full pixel dimensions, even though the added area may be invisible.
Unequal opposing extensions reposition the source within the result. They do not keep it centered automatically.

Common questions

Will extending the canvas stretch or crop my original image?

No. Canvas extension increases the area surrounding the source rather than changing the source's pixel dimensions. The original is offset by the space added on the left and top. Cropping would remove existing pixels, while resizing would resample them; neither operation is the purpose of this tool.

How do I keep the original image centered?

Add the same number of pixels to the left and right, and the same number to the top and bottom. If the total increase on an axis is an odd number of pixels, it cannot be divided equally into whole pixels, so one side must receive one additional pixel.

References and verification

The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.