Sometimes when I export enlarged image as png, it is saved as 16-bit image, despite “Bit depth” option being set to “8-bit” or “Preserve”. Depending on image, “Bit depth” may or may not work properly. But for the same image, this option works identical for multiple export runs.
Seems like in “7.2.0” the problem was fixed. Until this version Gigapixel sometimes generated 16-bit pictures. After update I wasn’t able to repeat this problem.