Systems and methods for producing blot images. A blot, for example a western blot, is imaged using an imaging system having a field of view and a magnification. Features of interest in the blot correspond to features in the digital image, and the sizes of the features in the digital image depend on the magnification of the imaging system. A structuring element is selected based on the sizes and shapes of the features in the digital image, and the image is morphologically eroded and dilated varying numbers of times. The eroded and dilated image is subtracted from the original blot image to remove background signal from the blot image, producing an output image. The number of erosions needed to completely erode the features of interest is determined automatically, for example by investigating the behavior of the kurtosis of the output image as a function of the number of erosions performed.
