| ::area_center | Area and center of regions. |
| ::circularity | Shape factor for the roundness of a region. |
| ::compactness | Shape factor for the compactness of a region. |
| ::connect_and_holes | Number of connection components and holes |
| ::contlength | Contour length of a region. |
| ::convexity | Shape factor for the convexity of a region. |
| ::diameter_region | Maximal distance between two boundary points of a region. |
| ::eccentricity | Shape features derived from the ellipse parameters. |
| ::elliptic_axis | Parameters of the equivalent ellipse. |
| ::euler_number | Calculate the Euler number. |
| ::find_neighbors | Search direct neighbors. |
| ::get_region_index | Index of all regions containing a given pixel. |
| ::get_region_thickness | Access the thickness of a region along the main axis. |
| ::hamming_distance | Hamming distance between two regions. |
| ::hamming_distance_norm | Hamming distance between two regions using normalization. |
| ::inner_circle | Largest inner circle of a region. |
| ::moments_region_2nd | Geometric moments of regions. |
| ::moments_region_2nd_invar | Geometric moments of regions. |
| ::moments_region_2nd_rel_invar | Geometric moments of regions. |
| ::moments_region_3rd | Geometric moments of regions. |
| ::moments_region_3rd_invar | Geometric moments of regions. |
| ::moments_region_central | Geometric moments of regions. |
| ::moments_region_central_invar | Geometric moments of regions. |
| ::orientation_region | Orientation of a region. |
| ::roundness | Shape factors from contour. |
| ::runlength_distribution | Distribution of runs needed for runlength encoding of a region. |
| ::runlength_features | Characteristic values for runlength coding of regions. |
| ::select_region_point | Choose all regions containing a given pixel. |
| ::select_region_spatial | Pose relation of regions. |
| ::select_shape | Choose regions with the aid of shape features. |
| ::select_shape_proto | Choose regions having a certain relation to each other. |
| ::select_shape_std | Select regions of a given shape. |
| ::smallest_circle | Smallest surrounding circle of a region. |
| ::smallest_rectangle1 | Surrounding rectangle parallel to the coordinate axes. |
| ::smallest_rectangle2 | Smallest surrounding rectangle with any orientation. |
| ::spatial_relation | Pose relation of regions with regard to the coordinate axes. |
| ::test_region_point | Test if the region consists of the given point. |