9.13. Canvas Size

9.13. Canvas Size
	9. The “Image” Menu of the Image Window

Revision History
Revision $Revision: 1748 $	2006-07-28	scb

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 without modifying the contents of the layers in the image. 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.

9.13.1. Activating the Command

You can access this command from the image menubar through Image → Canvas Size.

9.13.2. Description of the “Canvas size” dialog

Figure 15.67. The “Canvas size” dialog

Canvas Size

Width; Height

You can set the Width and the Height of the canvas. The default units are pixels but you can choose different units, e.g. percent, if you want to set the new dimensions relative to the current dimensions. If the Chain to the right of the Width and Height is not broken, both Width and Height keep the same relative size to each other. That is, if you change one of the values, the other one also changes a corresponding amount. If you break the Chain by clicking on it, you can set Width and Height separately.

Whatever units you use, information about the size in pixels and the current resolution are always displayed below the Width and Height fields. You cannot change the resolution in the Canvas Size dialog; if you want to do that, use the Print Size dialog.

Offset

The Offset values are used to place the image on the canvas. The preview window displays the image in a frame with a thin border. When the canvas is smaller than the image, the preview window shows it in a frame with a thin black border.

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.
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
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).

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).