1. A computer-implemented method, comprising: receiving a selection of at least one pixel in an input image comprising a plurality of pixels, wherein the selection of the at least one pixel comprises a color and a location within the input image; determining a color model based on the color and the location of the at least one pixel, wherein the color model comprises one or more truncated Gaussian functions; and generating a soft mask based on the color model, wherein the soft mask comprises a respective value indicating a degree of membership in the soft mask for each of the plurality of pixels in the input image, wherein the degree of membership in the soft mask is a function of a similarity in color to the at least one pixel in the selection, wherein the degree of membership in the soft mask is a function of a proximity to the location of the at least one pixel in the selection, and wherein the respective value for at least one of the plurality of pixels is an intermediate value between a minimum value and a maximum value.