Parameters of the 3x3 Custom Filter command

Filter Weights

The weight for each element of the filter kernel. After entering weights, you can normalize the filter to unit weight by clicking the [Normalize] button.

Normalize

The Normalize check box normalizes the filter to have a sum of all weights equal to 1.0. Another way to say this is that it causes the filter kernel to be scaled to unit volume underneath the weight profile.

Use Cursor ROI

If you check this item, only the region inside the Image Cursor is filtered.

Tip

Be careful not to use Normalize when the filter weights sum to 0 (see the above example). Many operators such as gradient filters normalize to 0 whereas a sharpening filter, for example, normalizes to a value of 1.