1. A computer-implemented process for creating a composite image, comprising using a computer to perform the following process actions: (a) inputting an image stack comprising a set of original images taken of generally the same subject matter over time and an initial empty paint image; (b) selecting one of the images from the image stack as a base for a composite image; and (c) drawing a first region around a portion of the composite image that is to be replaced by a portion of a source image and recording a set of labels wherein each label represents one of the source images; (d) deleting everything in the paint image in a second region corresponding to and fitting just inside the drawn first region at the same location as in the composite image; (e) selecting one of the images from the image stack as a source image to replace the portion of the composite image; (f) defining a third region in the paint image slightly smaller than the size of the second region with the center located at the same location as the center of the second region and specifying a label for each of the pixels of this third region with the label for the selected source image; (g) using an optimization procedure to compute a complete label image such that the label image agrees with the paint image within the third region and minimizes artifacts at transitions between labels; (h) using the label image to create the composite image by copying pixels from the source images by selecting them according to their label; (i) if all desired changes are not made, repeating process actions (c) through (h); and (j) if all desired changes are made, outputting the composite image as the final composite image.