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# Customizing Filters

Although the filter library contains a number of special effects filters, you may need custom filters for specialized applications.

When a filter is applied to an image, the colour value of each pixel in the image is evaluated individually and is modified in one of two ways:

- A matrix-based spatial filter modifies each pixel according to calculations performed on its surrounding pixels.
- A procedural filter modifies each pixel in a predefined way.

A filter is composed of up to five matrix or procedural image operations. These operations are performed in sequence so the output from one operation becomes the input to the next. When these operations are combined, they are called filter elements to distinguish them from the final composite filter. Matrix and procedural filter elements can be combined within a single filter.

#### Topics in this section

- Using Matrix Filter Elements
- Using Procedural Filters
- Saving Custom Filters