| iTool User's Guide: Common Operations |

## Operations on Regions of Interest

A region of interest (or ROI) is an area that contains data you wish to identify. An ROI can be drawn anywhere within your image and can be selected from rectangular, elliptical, polygonal, and freehand region of interest buttons on the iImage Image Panel. You can also apply operations to image data contained within an ROI area.

Some operations applied to ROIs affect the ROI data while others affect the ROI vertices.

### Operations Modifying ROI Data

If the operation acts on the pixel values of the underlying data, the pixels that are contained within the ROI are changed as a result of the operation. Pixel values outside of the ROI area remain unchanged but pixel values within the ROI are set to correspond with the pixel result of the chosen operation.

Examples of operations acting upon the ROI data are:

- Filter operations including Convolution, Median, Smooth, Roberts, and Sobel

- Morphological operations

- Transform operations including scaling and inverting data

### Operations Modifying ROI Vertices

If the operation acts on the vertices of the ROI itself, the vertices are changed as a result of the operation. If the entire image is selected for an operation, the ROI will follow the behavior of the entire image as the operation acts upon it. If only the ROI is selected, then only the ROI will respond to the operation.

Examples of operations acting upon the ROI vertices are:

- Rotate right, left, or by a specified angle

- Flip horizontal or vertical

- Region grow

IDL Online Help (March 01, 2006)