Main Content

ROI-Based Processing

Define and operate on regions of interest (ROI)

A region of interest (ROI) is a portion of an image that you want to filter or operate on in some way. You can represent an ROI as a binary mask image. In the mask image, pixels that belong to the ROI are set to 1 and pixels outside the ROI are set to 0. The toolbox offers several options to specify ROIs and create binary masks.

The toolbox supports a set of objects that you can use to create ROIs of many shapes, such circles, ellipses, polygons, rectangles, and hand-drawn shapes. After you create the objects, you can modify their shape, position, appearance, and behavior. For more information about the ROI shapes, see Create ROI Shapes.


expand all

AssistedFreehandAssisted freehand region of interest
CircleCircular region of interest
CrosshairCrosshair region of interest (Since R2019b)
CuboidCuboidal region of interest
EllipseElliptical region of interest
FreehandFreehand region of interest
LineLine region of interest
PointPoint region of interest
PolygonPolygonal region of interest
PolylinePolyline region of interest
RectangleRectangular region of interest
drawassistedCreate customizable freehand ROI with assistance from object edges
drawcircleCreate customizable circular ROI
drawcrosshairCreate customizable crosshair ROI (Since R2019b)
drawcuboidCreate customizable cuboidal ROI
drawellipseCreate customizable elliptical ROI
drawfreehandCreate customizable freehand ROI
drawlineCreate customizable linear ROI
drawpointCreate customizable point ROI
drawpolygonCreate customizable polygonal ROI
drawpolylineCreate customizable polyline ROI
drawrectangleCreate customizable rectangular ROI
drawBegin drawing ROI interactively
reduceReduce density of points in ROI (Since R2019b)
beginDrawingFromPointBegin drawing ROI from specified point
inROIQuery if points are located in ROI
bringToFrontBring ROI to front of Axes stacking order
waitBlock MATLAB command line until ROI operation is finished (Since R2019b)
createMaskCreate binary mask image from ROI
roipolySpecify polygonal region of interest (ROI)
poly2maskConvert region of interest (ROI) polygon to region mask
regionfillFill specified regions in image using inward interpolation
inpaintCoherentRestore specific image regions using coherence transport based image inpainting
inpaintExemplarRestore specific image regions using exemplar-based image inpainting (Since R2019b)
roicolorSelect region of interest (ROI) based on color
roifilt2Filter region of interest (ROI) in grayscale image
reducepolyReduce density of points in ROI using Ramer–Douglas–Peucker algorithm (Since R2019b)


Specify ROIs

Filter ROIs

Create Interactive ROIs Using Events and Callback Functions