You can resize an image by choosing Image > Resize > Image . This brings up the Resize Image dialog box.

Image Size

You can specify the new width and height, or the percentage for scaling. If you check the Maintain aspect ratio option, your inputs in the new width, height and scale fields will affect each other to ensure that the resizing does not distort the aspect of the image.

Interpolation

Pixels are added to the image when resizing up, and reduced when resizing down. The interpolation methods specify how the pixels are added or reduced.

• Nearest neighbor  duplicates or discards the neighboring pixels during resize. This operation is fast but it also produces blocky images, or loses details in the resized image.
• The Linear, Bilinear, Bicubic and Natural sampling methods calculate the pixels in the resized image using all pixels in the original image. They use different algorithms when calculating the pixels and can be slow when working with large images. All these methods produce good quality but slightly blurry images. If you want, you can  sharpen the image after resizing it.

Canvas

Canvas is the visible rectangular area where the image and image selection are positioned and displayed. When the image or selection are moved outside the canvas, it will be obscured and clipped by the canvas. You can change the size of the canvas using Image > Resize > Canvas. This bring sup the Canvas Size dialog box.

You can then specify the new width and height of the canvas. If the new canvas is larger than the existing canvas, use the Horizontal and Vertical image Alignment options to control how the image and image selection will be re-positioned in the new canvas.

To adjust the canvas to the most compact size that reveals all parts of the image and selection, choose Image > Resize > Fit Canvas to Image or click this button  on the toolbar. This is useful when the image or selection has been resized, cropped or moved.