A system for analyzing thin section images is disclosed. A microscope scans a thin section impregnated by a dyed epoxy and develops a digital representation of the color image of the thin section. A classifier defines the areas of the image which are identified as pore space. The color image is then transformed into a monochromatic image by transforming the color image onto the principal axis representing the brightness of the color image. Each discrete feature representing grain space or pore space in the monochromatic image is defined by analyzing the uniform brightness distribution of the region. Finally, the boundary of each discrete region can be processed to ascertain the size, shape, orientation and roundness of the region.