Combination of multiple images for flash re-lightning

This paper introduces a novel way to combine multiple images of the same scene in order to improve the visual appearance. Especially, images taken with the flash often contain artifacts such as too strong flash illumination and too dark background. The nature of the ambient lightning can be combined back with other image features. Two or more flash/no-flash images are combined to a spatially adaptive mixture image that represents the essential features of the images. No assumptions are made on which images contribute to the result. The lightning, shadows, and colors are a blind combination of the input images. The new method uses the principal component analysis (PCA) to find an optimal fusing factors for the images in order to compute the resulting image. The images are decomposed and processed using PCA to find out the local adaptive principal component. Image decomposition prior to PCA makes it possible for both coarse and fine image features to be fused. Also other camera parameters than the flash can be varied. For instance, if images with multiple focus settings are fused by the new APC (adaptive principal combination) method, the resulting mixture image depicts an extended depth of focus.