Step 1

In order to use the NIH Image Analyze menu to perform an image analysis on the grain boundary map, the outlines have to be two pixels wide, and the cross sectional areas of the grains have to be black. To exclude areas that intersect the boundary of the image from the analysis, a rim of 6 pixel width is cut off using key 5. The outlines are thickened (key t), the rim area is filled with black using the regular filling tool of NIH Image, and the image is inverted (key y).

Lazy grain boundaries 5 trim off a rim of 6 pixels width t thicken outlines y invert image => areas

Start GRAIN SIZE ANALYSIS step 1 - step 2 - step 3 - step 4 - step 5