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 digital data defining pixel colors of a two-dimensional pixel array; (2) receiving, by the computer system, a display command to display a second image which is a 2D image defined by digital 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 digital data defining pixel colors of a two-dimensional pixel array, wherein editing of each image comprises editing digital data representing the image in response to one or more editing commands; and (3) in response to the display command, processing, by the computer system, the second image to obtain a processed image defined by digital data defining pixel colors of a two-dimensional pixel array, and providing the processed image to the computer display system; (4) wherein the processing comprises: (4A) the computer system using one or more predefined types of operations to select, from the editing commands, each editing command involving any one of the one or more predefined types of operations; wherein the one or more predefined types of operations do not include at least one type of color modification in an image on which the operation is to be performed; (4B) the computer system deriving the processed image from each selected editing command but not from any deselected editing command, and from the digital data representing the second image; wherein at least one of the following statements (i), (ii), (iii) (iv) is true: (i) the one or more predefined types of operations include any type that modifies the size of at least one element of an image on which the operation is to be performed without removing the element from the image; and 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 one or more predefined types of operations include any type that modifies the orientation of an image on which the operation is to be performed; and the first and second images have different orientations, but the processed image has the same orientation as the first image; and/or (iii) the one or more predefined types of operations include any type that trims away a portion of an image on which the operation is to be performed; and 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 one or more predefined types of operations include at least one type that combines an image on which the operation is to be performed with another image; and 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, the third image being introduced into the first image using said at least one type that combines an image with another image.