# Masking

You can use an arbitrarily defined mask to exclude portions of an image from blob analysis. The image mask does not have to be the same size as the image. To mask an image prior to blob analysis, you align the image mask with the image by specifying the distance offset of the upper-left corner of the image mask to the image, in the coordinate system values of the image.

You can use masking to remove features from an image that would make segmenting the image difficult or impossible. The following figure shows the use of a mask.