images.roi.Circle class

Package: images.roi

Circular region of interest

Description

The images.roi.Circle class creates a circular region-of-interest (ROI) object. You call the draw method of the object to begin drawing the ROI interactively by using your mouse.

To draw the ROI interactively, move the pointer over the axes, click and drag the pointer to draw the circle. To finish drawing, release the pointer. To delete the ROI, position the pointer over the circle, right-click, and select Delete Circle from the context menu. For more information about interactive behaviors including keyboard shortcuts, see Tips.

The images.roi.Circle class is a handle class.

Creation

Description

h = images.roi.Circle creates an instance of the images.roi.Circle class with default properties.

example

h = images.roi.Circle(ax) creates the ROI on the axes specified by ax.

example

h = images.roi.Circle(___,Name,Value) modifies the appearance or behavior of the ROI by specifying values for one or more ROI properties. You can set properties using name-value pairs with or without specifying an axes.

Input Arguments

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Parent of the ROI, specified as an Axes object.

Properties

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Public Properties

Center of the ROI, specified as a 1-by-2 numeric array of the form [x y]. The values x and y are the coordinates of the center point of the ROI. The value of this property changes automatically when you draw or move the ROI.

ROI color, specified as a MATLAB® ColorSpec (Color Specification).

Example: 'green'

Example: 'g'

Example: [0 1 0]

ROI can be interactively deleted via a context menu, specified as true or false. When the value is true (default), you can delete the ROI via the context menu. To disable this context menu item, set this property to false. When the value is set to false, you can still delete the ROI by calling the delete function specifying the handle to the ROI as the input.

Area of the axes in which you can interactively place the ROI, specified as one of the values in this table.

ValueDescription
'auto'The drawing area is the current axes limits (default).
'unlimited'The drawing area has no boundary and ROIs can be drawn or dragged to extend beyond the axes limits.
[x,y,w,h]The drawing area is restricted to a rectangular region beginning at (x,y), and extending to width w and height h.

Transparency of the ROI face, specified as a numeric scalar value in the range [0 1]. When the value is 1, the ROI face is fully opaque. When the value is 0, the ROI face is completely transparent.

ROI face can capture clicks, specified as true or false. When true (default), the ROI face captures mouse clicks. When false, the ROI face does not capture mouse clicks.

Visibility of the ROI handle in the Children property of the parent, specified as one of the values in this table.

ValueDescription
'on'The object handle is always visible (default).
'off'The object handle is hidden at all times.
'callback' The object handle is visible from within callbacks or functions invoked by callbacks, but not from within functions invoked from the command line.

Interactivity of the ROI, specified as one of the values in this table.

ValueDescription
'all'The ROI is fully interactable (default).
'none'The ROI is not interactable, and no drag points are visible.
'translate'The ROI can be translated (moved) within the drawing area but not reshaped. This value is not available for use with images.roi.Point objects.
'reshape'The ROI can be reshaped but not translated. This value is not available for use with images.roi.Point objects or images.roi.Rectangle objects.

ROI label, specified as a character vector or string. By default, the ROI has no label ('').

Width of the ROI edge, specified as a positive numeric scalar in points. The default value is three times the number of points per screen pixel.

ROI parent, specified as an Axes object. A UIAxes cannot be the parent of the ROI.

Radius of the circle, specified as a nonnegative numeric scalar. You can also set this property by drawing or resizing the circle.

Selection state of the ROI, specified as the logical value true or false. You can also set this property interactively. For example, clicking on the ROI selects the ROI and sets this property to true. Similarly, pressing the Ctrl key and clicking the ROI deselects the ROI and sets the value of this property to false.

Color of the ROI when selected, specified as a MATLAB ColorSpec (Color Specification). The intensities must be in the range [0,1]. If 'SelectedColor' is set to 'none', then the value of Color defines the color of the ROI for all states, selected or not.

Example: 'green'

Example: 'g'

Example: [0 1 0]

Color of the ROI stripe, specified as a MATLAB ColorSpec (Color Specification) value. By default, the edge of an ROI is solid colored. If you specify StripeColor, the ROI edge is striped. The striping consists of a combination of the value specified by 'Color' and this value.

Example: 'green'

Example: 'g'

Example: [0 1 0]

Tag to associate with the ROI, specified as a character vector or string. Use the tag value to find the ROI object in a hierarchy of objects using the findobj function.

Context menu, specified as a ContextMenu object. Use this property to display a custom context menu when you right-click the ROI. You can create a custom context menu by using the uicontextmenu function and then configuring context menu properties.

Data to associate with the ROI, specified as any MATLAB data. For example, you can specify a scalar, vector, matrix, cell array, string, character array, table, or structure. MATLAB does not use this data.

Locations of points on the edge of the ROI, returned as an n-by-2 array, where n is the total number of vertices.

This property is read-only.

ROI visibility, specified as one of the values in this table.

ValueDescription
'on'Display the ROI (default).
'off'Hide the ROI without deleting it. You still can access the properties of an invisible ROI.

Methods

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Events

Event NameTriggerEvent DataEvent Attributes
DeletingROIROI is about to be interactively deleted.event.EventData

NotifyAccess: private

ListenAccess: public

DrawingStartedROI is about to be interactively drawn.event.EventData

NotifyAccess: private

ListenAccess: public

DrawingFinishedROI has been interactively drawn.event.EventData

NotifyAccess: private

ListenAccess: public

MovingROIROI shape or location is being interactively changed.images.roi.CircleMovingEventData

NotifyAccess: private

ListenAccess: public

ROIMovedROI shape or location has been interactively changed.images.roi.CircleMovingEventData

NotifyAccess: private

ListenAccess: public

ROIClickedROI has been clicked. images.roi.ROIClickedEventData

NotifyAccess: private

ListenAccess: public

Examples

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Read an image into the workspace and display it.

I = imread('baby.jpg');
figure
imshow(I)

Create a circular ROI on the image. Use the 'Center' property to specify the location and the 'Radius' property to specify the size. For programmatically created ROIs, if you want the ROI drawn in a specific axes, you must specify that axes as an input argument. Otherwise, an instance of the images.roi.Circle class is created but not displayed. In this example, specify the current axes (gca) to draw the ROI on the image in that axes.

h = images.roi.Circle(gca,'Center',[1000 1000],'Radius',500);

Tips

  • The ROI supports the following interactivity, including keyboard shortcuts.

    BehaviorKeyboard shortcut
    Stop drawing the ROI.Press Esc. The function returns a valid ROI object with an empty Position field.
    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.
  • For information about using an ROI in an app created with App Designer, see Using ROIs in Apps Created with App Designer.

Introduced in R2018b