drawellipse
Create customizable elliptical ROI
Description
roi = drawellipseEllipse object and enables interactive drawing of an
elliptical 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 elliptical 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
drawellipse is a convenience function for creating an
Ellipse ROI object. If you create the ROI object
directly, calling Ellipse, you must call the draw object
function to enable interactive drawing of the ROI. In contrast, the
drawellipse 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 = drawellipse(___,Name,Value)
Examples
Create Red Elliptical ROI
Read an image into the workspace and display it.
imshow(imread('llama.jpg'))
Interactively draw a red elliptical ROI.
h = drawellipse('Color','r');
Change the stripe color of the ROI to black, then increase the opacity of the ROI.
h.StripeColor = 'k';
h.FaceAlpha = 0.4;
Create Elliptical ROI Programmatically
Read an image into the workspace and display it.
I = imread('baby.jpg');
figure
imshow(I)
Draw an elliptical ROI on the image. Use the 'Center' name-value pair to specify the location of the ellipse and the 'SemiAxes' name-value pair to specify the shape of the ellipse. Set the edge of the ellipse to be a striped red line by specifying the 'StripeColor' name-value pair.
h = drawellipse('Center',[1000,1000],'SemiAxes',[500,250],'StripeColor','r');
Set Up Listener for Ellipse 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 = drawellipse('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.Fine-tune width of ellipse as you are drawing. As you draw the ellipse, use the scroll wheel to make small changes to the width of the ellipse. Rotate the ROI. Position the pointer near a vertex. The pointer changes to the rotate pointer. Click and rotate the ROI on its center.
To make the rotation snap at 15 degree angles, press Shift as you rotate.
Maintain aspect ratio while drawing. Hold the Shift key as you draw. Creates a circular ROI.
To lock the aspect ratio, position the pointer on the ROI, right-click, and select Fix Aspect Ratio from the context menu
Resize (reshape) the ROI. Position pointer over a vertex and then click and drag. To main the aspect ratio as you resize, Hold the Shift key.
Move the ROI. Position the pointer over the ROI. The pointer changes to the fleur shape. Click and drag to move the ROI. Delete the ROI. Position the pointer over the ROI and right-click to view its context menu. Select Delete Ellipse from the menu. You can also delete the ROI using the deleteobject function.The
drawellipsefunction returns anEllipseROI 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
Ellipseobject, see Set Up Listener for Ellipse ROI Events. For more details about these capabilities, see theEllipseobject documentation.
Compatibility Considerations
See Also
drawassisted | drawcircle | drawcrosshair | drawcuboid | drawfreehand | drawline | drawpoint | drawpolygon | drawpolyline | drawrectangle | Ellipse