The -colors or -monochrome option, or saving to a file format which requires color reduction, is required for this option to take effect. The comment is not drawn on the image, but is embedded in the image datastream via a "Comment" tag or similar mechanism.
Specify "ieeefp" in order to write floating-point TIFF files with float bit or double bit values.
The floating point data is currently not scanned in advance to determine a best maximum sample value so if the range is not 1. The set of images is terminated by the appearance of any option. If samples are not packed, the DPX standard recommends type A padding. Note this differs from over because the portion of change-image outside base-image's shape does not appear in the result.
Show me the code! The default maximum is scans. Threshold : that's mainly used to avoid sharpening noise.