1. A computer-implemented method for image processing, the method comprising: (1) providing, by a computer system, a first image to a computer display system, the first image being a 2D image defined by image data defining pixel colors of a two-dimensional pixel array; (2) receiving, by the computer system, a command to display a second image which is a 2D image defined by image data defining pixel colors of a two-dimensional pixel array, wherein the first image was obtained by editing the second image and/or the first and second images were obtained by editing a common image which is a 2D image defined by image data defining pixel colors of a two-dimensional pixel array; and (3) in response to the command, processing, by the computer system, the second image to obtain a processed image defined by image data defining pixel colors of a two-dimensional pixel array, and providing the processed image to the computer display system; wherein: operation (3) comprises re-sizing the second image to obtain the processed image so that each element of the processed image which corresponds to an element of the first image is displayed with the same size as the element of the first image; and/or (ii) the first and second images have different orientations, but the processed image has the same orientation as the first image; and/or (iii) the second image is processed to trim away a portion which corresponds to a portion trimmed away from the first image; and/or (iv) the second image is combined with a third image to obtain the processed image, wherein the third image is a component of the first image but not of the second image.