9.11.  Canvas Size

Revision History
Revision $Revision: 2416 $ 2007-11-14 j.h

The “canvas” is the visible area of the image. By default the size of the canvas coincides with the size of the layers. The Canvas Size command lets you enlarge or reduce the canvas size. You can, if you want, modify the size of the layers. When you enlarge the canvas, you create free space around the contents of the image. When you reduce it, the visible area is cropped, however the layers still extend beyond the canvas border.

When you reduce the canvas size, the new canvas appears surrounded with a thin negative border in the preview. The mouse pointer is a moving cross: click and drag to move the image against this frame.

Offset

The Offset values are used to place the image on the canvas. You can see the size and the content of the canvas in the preview of the dialog window. When the canvas is smaller than the image, the preview window shows it in a frame with a thin negative border. You can also modify the offset by click-and-dragging on the preview.

X ; Y

The X and Y parameters specify the coordinates of the upper left corner of the image relative to the upper left corner of the canvas. When the canvas is smaller than the image, the X and Y values are negative. You can change these values by using the text boxes. The default units are pixels, but you can choose different units. By clicking on the arrows next to the text boxes, you can move the image one pixel at a time. You can move the image ten pixels at a time by clicking on the arrows while pressing the Shift key.

Layers

Before the GIMP-2.4 version, “Canvas Size” had no influence on layer size. To change it, you had to use the Layer Boundary Size command. The “Layers” option now allows you to specify how, possibly, layers will be resized. The drop-down list offers you several possibilities:

  • None: default option. No layer is resized, only the canvas is.

  • All Layers: all layers are resized to canvas size.

  • Image-sized layers: only layers with the same size as the image are sized to canvas size.

  • All visible layers: only visible layers, marked with a icon, in the Layer Dialog, are sized to canvas size.

  • All linked layers: only linked layers, marked with a in the Layer Dialog, are sized to canvas size.

Center

The Center button allows you to center the image on the canvas. When you click on the Center button, the offset values are automatically calculated and displayed in the text boxes.

[Note] Note

When you click on the Resize button, the canvas is resized, but the pixel information and the drawing scale of the image are unchanged.

If the layers of the image did not extend beyond the borders of the canvas before you changed its size, there are no layers on the part of the canvas that was added by resizing it. Therefore, this part of the canvas is transparent and displayed with a checkered pattern, and it is not immediately available for painting. You can either flatten the image, in which case you will get an image with a single layer that fits the canvas exactly, or you can use the Layer to Image Size command to resize only the active layer, without changing any other layers. You can also create a new layer and fill it with the background you want. By doing this, you create a digital “passe-partout” (a kind of glass mount with a removable back for slipping in a photograph).