This topic describes how to use the ENVI Classic ROI Tool. See Regions of Interest for the recommended method for using ROIs in ENVI.

For complete details on using the ROI Tool, refer to the topic "Defining ROIs" in the ENVI Classic Help. Here are some basic steps for creating ROIs:

  1. In the ROI Tool, select the Window you want to use for adding the ROI. The choices are Image, Scroll, and Zoom. To disable ROI mode, select Off.
  2. From the ROI Tool dialog menu bar, select ROI_Type and select one of the following options.
    • Polygon: (default) Left-click on the image or plot to add polygon vertices. Right-click to complete the polygon.
    • Polyline: Left-click on the image to add polyline vertices. Right-click to complete the polyline.
    • Point: Left-click on the image to add points.
    • Rectangle: Left-click and drag on the image to draw the rectangle, or middle-click to draw a square.
    • Ellipse: Left-click and drag on the image to draw the ellipse, or middle-click to draw a circle.
    • Multi Part: On/Off: Use multi part mode to draw ROIs with holes in them, or donut ROIs. You cannot draw multi part ROIs using point or polyline ROIs. Left-click and drag on the image to draw the base shape. Right-click to fill the ROI. Draw any number of additional ROIs or parts within the first ROI to create holes (holes cannot cross the path of any other shape within its group). The ROIs do not fill in when you right-click the second time.
    • Input Points from ASCII: Select an ASCII file that contains ROI data. Enter the column numbers for the x and y point coordinates. Select the type of ROI that the points define from the These points comprise drop-down list. For polygon and polyline ROIs, the ASCII points define the vertices of the ROI. Select whether the input coordinates are Pixel Based or Map Based. If you select Map Based, select the projection type and enter the zone and datum information as needed.
  3. After adding parts to the ROI, right-click a third time to accept the multi-part ROI. ENVI fills in the base ROI and removes the parts to reveal holes in the base ROI.
  4. Use the colored diamond-shaped handle if you need move the ROI to another location.
  5. Right-click to accept the ROI placement.