Neighbourhood operations pose a problem. What happens when the neighbourhood operator operates near the border of the image and needs data from the area outside the image? The usual solution, also adopted by DIPlib, is to silently extend the image. There are various ways of extending the boundary. Below is a list of the possible methods. More details can be found in the user guide. Note that not all functions support all of these.
| Name | Description |
| DIP_BC_SYM_MIRROR | Symmetric mirroring |
| DIP_BC_ASYM_MIRROR | Asymmetric mirroring |
| DIP_BC_PERIODIC | Periodic copying |
| DIP_BC_ASYM_PERIODIC | Asymmetric periodic copying |
| DIP_BC_ADD_ZEROS | Extending the image with zeros |
| DIP_BC_ADD_MAX_VALUE | Extending the image with +infinity |
| DIP_BC_ADD_MIN_VALUE | Extending the image with -infinity |