A comparison of different intensity gradient formulae for orientation analysis of electron micrographs

A detailed study of different intensity gradient formulae was conducted using 91 separate images covering a wide range of microfabric. It was found that a formula based on the 3 × 3 local pixel array gives almost identical results over all images with the standard formula based on 20 pixels forming a circular grouping within the 5 × 5 local array. Other formulae based on other groupings of pixels within the same pixel arrays give markedly different results. Computation times are reduced up to 45% when the 8,5 formula is used in place of the 20,14 one, and would thus seem to have advantages when large numbers of images are to be processed. While all formulae give somewhat similar domain‐segmented images when viewed visually, differences are noted both in the number of segmented domains as well as in the area of domains in each orientation sector. It is possible that the radius of the modal filter selected for the domain segmentation should be varied according to the formula type used.