Dear Changgong Lee, Thank you for this report.
This potential division by zero could only happen if the user of tiffmakemosaic provided a zero-width or a zero-length (or both) TIFF input image, which is illegal according to the standard LibTIFF.
However, to be on the safe side, e.g. if tiffmakemosaic was compiled against a non-standard implementation of the TIFF library, a fix was added in version 1.4.2 of the largetifftools.
Best wishes, Christophe Deroulers
