US Patent 9438769 Preserving smooth-boundaried objects of an image

In one example, a method of automatically enhancing a digital image having a smooth-boundaried foreground object. The method processes the image via gradient-based background segmentation at a first scale to generate a first mask. The first mask has a first accuracy. The first mask is used to generate a first background of the image which includes at least a portion of the smooth-boundaried foreground object. The method further processes the first background via gradient-based background segmentation at a smaller second scale to generate a second mask. The second mask has a greater second accuracy. The second mask is used with the first mask to generate a second background of the image which substantially excludes the smooth-boundaried foreground object. The image can be enhanced using the second background so as to preserve the smooth-boundaried foreground object.