# Defining a Search Region

By default the tool searches the entire run-time image for the trained pattern, but you can define a smaller search region in applications where the trained pattern must appear in a predictable area. The tool supports several shapes for a search region such as ellipses, rectangles, and affine rectangles.

Regardless of which shape you choose, the tool encloses the region with a bounding box for the search algorithm. By default the tool masks out any pixels that fall outside the search region but within the bounding box, so any trained pattern outside the search region is not found:

You can choose to use a bounding box without a mask, where trained features outside the search region but inside the bounding box can still be found by the search algorithm: