drawrectangle
Create customizable rectangular ROI
Description
roi = drawrectangleRectangle object and enables interactive drawing of a
rectangular region-of-interest (ROI) on the current axes.
To draw the ROI, position the pointer on the image. The cursor changes to a fleur shape. Click and drag to draw the rectangular ROI. To finish the ROI, release the mouse button. For more information about using the ROI, including keyboard shortcuts and context menu options, see Tips.
Note
drawrectangle is a convenience function for creating a
Rectangle ROI object. If you create the ROI object
directly, calling Rectangle, you must call the draw object
function to enable interactive drawing of the ROI. In contrast, the
drawrectangle function creates the ROI object and
calls the draw object function for you. Whichever way you
create the ROI, you use object properties, object functions, and event
notifications to customize its appearance and behavior. For more information
about using these capabilities, see Tips.
roi = drawrectangle(___,Name,Value)
Examples
Draw Nested Rectangular ROIs
Read an image into the workspace and display it.
imshow(imread('baby.jpg'))Draw a red rectangular ROI with the label 'OuterRectangle'.
r1 = drawrectangle('Label','OuterRectangle','Color',[1 0 0]);
Draw another rectangular ROI, restricting the drawing area to the area inside the first rectangle.
r2 = drawrectangle('Label','InnerRectangle','DrawingArea',r1.Position);
Create Rectangular ROI Programmatically
Read image into the workspace and display it.
I = imread('baby.jpg');
figure
imshow(I)
Draw a rectangular ROI over the image, using named parameters to specify the location and size of the rectangle. The example also specifies that the edge of the rectangle is a striped line.
h = drawrectangle('Position',[500,500,1000,1000],'StripeColor','r');
Set Up Listener for Rectangle ROI Events
Read an image into the workspace.
I = imread('cameraman.tif');Display the image.
imshow(I);
Draw a rectangular ROI on the image.
roi = drawrectangle('Color','r');
Set up listeners for ROI moving events. When you move it, the ROI sends notifications of these events and executes the callback function you specify.
addlistener(roi,'MovingROI',@allevents); addlistener(roi,'ROIMoved',@allevents);
The allevents callback function displays the previous position and the current position of the ROI.
function allevents(src,evt) evname = evt.EventName; switch(evname) case{'MovingROI'} disp(['ROI moving previous position: ' mat2str(evt.PreviousPosition)]); disp(['ROI moving current position: ' mat2str(evt.CurrentPosition)]); case{'ROIMoved'} disp(['ROI moved previous position: ' mat2str(evt.PreviousPosition)]); disp(['ROI moved current position: ' mat2str(evt.CurrentPosition)]); end end
Input Arguments
Output Arguments
Tips
The ROI supports the following interactivity, including keyboard shortcuts.
Behavior Keyboard shortcut Cancel drawing the ROI. Press Esc. The function returns a valid ROI object with an empty Positionfield.Resize (reshape) the ROI. Position pointer over a vertex and then click and drag. The rectangle has vertices at each corner and at the midpoint of each side. To preserve the aspect ratio while resizing, press the Shift key. To lock the aspect ratio, use the Fix Aspect Ratio in the right-click context menu.
Move the ROI. Position the pointer over the ROI. The pointer changes to the fleur shape. Click and drag the ROI. Delete the ROI. Position the pointer anywhere on the ROI and right-click. Select Delete Rectangle from the context menu. You can also delete the ROI using the deleteobject function.The
drawrectanglefunction returns aRectangleROI object. After creation, use these capabilities of the object to customize the appearance and behavior of the ROI.Object properties — ROI objects support properties that modify their appearance or behavior. For example, to change the color of the
roito yellow, set itsColorproperty,roi.Color = 'yellow'.Object functions — ROI objects support a set of object functions that operate on the ROIs. For example, if you want to pause the MATLAB command line after creating an ROI, call the
waitobject function.Event notifications — ROI objects can notify your code when certain events, such as being moved or clicked, happen to the ROI. To receive these notifications, use the
addlistenerobject function to set up listeners for specific events. In the listener, specify an event, such as'ROIMoved', and a callback function that executes when the event occurs. When the ROI notifies your application through the listener, it returns data specific to the event. For example, with the'ROIMoved'event, the ROI object returns its previous position and its current position.
For an example of using event listeners with the
AssistedFreehandobject, see Set Up Listener for Rectangle ROI Events. For more details about these capabilities, see theRectangleobject documentation.
Compatibility Considerations
See Also
drawassisted | drawcircle | drawcrosshair | drawcuboid | drawellipse | drawfreehand | drawline | drawpoint | drawpolygon | drawpolyline | Rectangle