Correct expUnderflow to avoid underflow (when checked in debug mode).
Renames "density" to "attenuation":
- Reflects more accurately the processed values.
- Avoids confusion with probability density concept.
Updates "gradient method":
- Computes the mean sum of absolute gradient for each set of voxels with the same attenuation, and defines threshold as the attenuation of the set of voxels between rock and pore attenuation peaks with the maximum mean sum of absolute gradient
- Supports both 8bit and 16bit source
- Removes anisotropy and assymetry errors kept for backward compatibility.
- Renames "gradient" to "difference" (gradient magnitude would be an L2 norm not L1).
- Outputs middle-threshold which is simply selected as the middle value between the two maximum peaks (rock and pore).
- Outputs threshold selection information
- Provides threshold=middle option to test against full gradient method.
Fix implementation factory registration.