Region-of-Interest Processing
It is sometimes of interest to process a single sub-region of an image
leaving other regions unchanged. This is commonly referred to as
region-ot-interest (ROI) processing. Here we show an example of edge
detection in a rectangular ROI using a real image. This loads the example
image.
![[Graphics:Images/Jankowski_ImageProcessing_gr_59.gif]](Images/Jankowski_ImageProcessing_gr_59.gif)
Here we define a region-of-interest. Image regions may be conveniently
selected using the mouse and keyboard. To select a particular region,
click the displayed graphics object. In Windows (for other systems consult
Input/Get Graphics Coordinates ), press the [Ctrl] key and click a point
of interest. The point will be selected. This may be repeated for as many
points as desired. Use the Copy and Paste command to paste the recorded
list of positions to any cell or expression in the notebook.
![[Graphics:Images/Jankowski_ImageProcessing_gr_60.gif]](Images/Jankowski_ImageProcessing_gr_60.gif)
![[Graphics:Images/Jankowski_ImageProcessing_gr_61.gif]](Images/Jankowski_ImageProcessing_gr_61.gif)
This shows the result of applying a Sobel edge detector to the region
defined by roi.
![[Graphics:Images/Jankowski_ImageProcessing_gr_62.gif]](Images/Jankowski_ImageProcessing_gr_62.gif)
![[Graphics:Images/Jankowski_ImageProcessing_gr_63.gif]](Images/Jankowski_ImageProcessing_gr_63.gif)
Further reading
User's Guide: Sections 5.6, 7.3.
Function Index: ImageRead, EdgeMagnitude, RegionProcessing, SobelFilter.
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