drawcircle
Create customizable circular ROI
Description
roi = drawcircleCircle ROI object and enables interactive drawing of a
circular 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 circular 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
drawcircle is a convenience function for creating a
Circle ROI object. If you create the ROI object
directly, calling Circle, you must call the draw object
function to enable interactive drawing of the ROI. In contrast, the
drawcircle 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 = drawcircle(___,Name,Value)
Examples
Create Black Circular ROI
Read an image into the workspace and display it.
imshow(imread('peacock.jpg'))
Interactively draw a partially-opaque black circular ROI.
h = drawcircle('Color','k','FaceAlpha',0.4);
Change the stripe color of the ROI to magenta, then increase the opacity of the ROI.
h.StripeColor = 'magenta';
h.FaceAlpha = 0.8;
Create Circular ROI Programmatically
Read an image into the workspace and display it.
I = imread('baby.jpg');
figure
imshow(I)
Draw a circular ROI on the image, Use the 'Center' name-value pair to specify the location of the circle and the 'Radius' name-value pair to specify its size. Set the edge of the circle to be striped by specifying the 'StripeColor' name-value pair.
h = drawcircle('Center',[1000,1000],'Radius',500,'StripeColor','red');
Set Up Listener for Circle ROI Events
Read an image into the workspace.
I = imread('cameraman.tif');Display the image.
imshow(I);
Draw a circular ROI on the image.
roi = drawcircle('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 the ROI. Position the pointer over one of the vertices on the circle and then click and drag. The aspect ratio of the ROI remains constant (1:1).
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 over the ROI and right-click to view its context menu. Select Delete Circle from the menu. You can also delete the ROI using the deleteobject function.The
drawcirclefunction returns aCircleROI 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
Circleobject, see Set Up Listener for Circle ROI Events. For more details about these capabilities, see theCircleobject documentation.
Compatibility Considerations
See Also
Circle | drawassisted | drawcrosshair | drawcuboid | drawellipse | drawfreehand | drawline | drawpoint | drawpolygon | drawpolyline | drawrectangle