Grain Mark
Mark grains by thresholding height, slope magnitude, or curvature. Thresholds are relative (0–1) to the data range. Small regions below min_size pixels are removed. Equivalent to Gwyddion's grain_mark.c module.
Inputs
| Name |
Type |
Required |
Description |
| field |
DATA_FIELD |
Yes |
Input surface |
Outputs
| Name |
Type |
Description |
| mask |
IMAGE |
Binary mask of marked grains |
Controls
| Name |
Type |
Default |
Description |
| criterion |
dropdown |
height |
What to threshold: height, slope, or curvature |
| threshold_low |
FLOAT |
0.3 |
Lower bound of the normalized threshold range (0–1) |
| threshold_high |
FLOAT |
1.0 |
Upper bound of the normalized threshold range (0–1) |
| min_size |
INT |
10 |
Minimum grain size in pixels; smaller regions are removed (1–100000) |
| inverted |
BOOLEAN |
False |
Invert the mask to mark valleys instead of peaks |
Notes
- Thresholds are relative to the data range: 0.0 = minimum value, 1.0 = maximum value.
- "slope" uses Sobel gradient magnitude — useful for marking edges and steep features.
- "curvature" uses the Laplacian — useful for marking bumps or pits regardless of absolute height.
- Use inverted=True to mark valleys, pores, or depressions instead of raised features.
- For Otsu-based automatic thresholding, use the Threshold Mask node instead.
