A computer program analyzes an image including features that correspond to emissions detected from a biological probe array. The program aligns one or more grids, each having one or more grid cells, with all or portions of the image; selects one or more grid cells to be associated with features based on distributions of pixel intensity values within the grid cells; locates a shape, such as a circle, in each selected grid cell based on distributions of pixel intensity values within the grid cells; and associates one or more intensity values with a feature based on intensities of feature pixels, or feature pixels and portions of feature pixels, within the shape located in the selected grid cell associated with the feature. The features may correspond to spots of biological material such as nucleic acid, peptide, protein fragment, protein, antibody, ligand, receptor, or small molecule.