1. A method of quantifying a feature represented by image data, comprising: receiving image data; determining a value indicative of an average intensity of each of a plurality of blocks in the image data, wherein the blocks include a primary block and outer blocks and the outer blocks surround the primary block, wherein each of the blocks includes an odd number of pixels greater than one and the odd number of pixels in each block is identical, wherein each block is centered on a center of a pixel, wherein the image data describes external pixels lying between the primary block and each of the outer blocks, wherein the external pixels do not contribute to the value indicative of the average intensity of any of the blocks; and comparing the value indicative of the average intensity of the primary block to each value indicative of the average intensity of each of the outer blocks; and quantifying a feature represented by the image data by generating a characteristic number based on the comparison.