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images.roi.AssistedFreehand class

Package: images.roi

Assisted freehand region of interest

Description

The images.roi.AssistedFreehand class creates an AssistedFreehand region-of-interest (ROI) object. You call the draw method of the object to begin drawing the ROI interactively by using your mouse. With assisted freehand, the line you are drawing follows the edges in the underlying image automatically.

To create an ROI interactively, position the pointer on the image, click and release to place the first vertex (waypoint), and then move the pointer to draw a line. The line snaps to nearby edges in the image automatically as you draw. Click to place vertices along the line as you draw. To finish the ROI and close the shape, double-click. To delete an ROI, position the pointer on the ROI (not on a vertex), right-click, and select Delete Freehand from the context menu. For more information about keyboard shortcuts, see Tips.

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

Creation

Description

example

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

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

h = images.roi.AssistedFreehand(___,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

Close the freehand ROI, specified as a logical value true or false. If true (default), images.roi.Freehand closes the ROI by connecting the last point drawn to the first point drawn.

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.

Image on which to draw ROI, specified as a handle to an Image object.

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.

Position of the ROI, specified as an n-by-2 numeric array of the form [x1 y1;...;xn yn], where n is the total number of vertices. Each row specifies the position of a point on the ROI edge.

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]

Smooth the edge of the freehand ROI using the standard deviation of the Gaussian smoothing kernel, specified as a nonnegative numeric scalar. The 'Smoothing' value filters the x and y coordinates of the freehand ROI. The filter size is 2*ceil(2*Smoothing) + 1.

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.

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.

Control points to reshape the freehand ROI, specified as an n-by-1 logical vector, the same length as Position. Each element of the Waypoints vector indicates if the corresponding point in the Position array is a waypoint. Positions that are waypoints are set to true in Waypoints. Dragging a waypoint modifies the ROI between the specified waypoint and its immediate neighboring waypoints. When you draw the freehand ROI, images.roi.AssistedFreehand automatically generates Waypoints at locations of increased curvature.

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.ROIMovingEventData

NotifyAccess: private

ListenAccess: public

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

NotifyAccess: private

ListenAccess: public

ROIClickedROI has been clicked. images.roi.ROIClickedEventData

NotifyAccess: private

ListenAccess: public

AddingWaypointA waypoint is about to be interactively added to the ROI.event.EventData

NotifyAccess: private

ListenAccess: public

WaypointAddedA waypoint has been interactively added to the ROI.event.EventData

NotifyAccess: private

ListenAccess: public

RemovingWaypointA waypoint is about to be interactively removed from the ROI.event.EventData

NotifyAccess: private

ListenAccess: public

WaypointRemovedA waypoint has been interactively removed from the ROI.event.EventData

NotifyAccess: private

ListenAccess: public

Examples

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Read an image into the workspace and display it.

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

Create an instance of an images.roi.AssistedFreehand class. By default, the class creates the ROI on the current axes. Note that the axes must contain an image.

h = images.roi.AssistedFreehand;

Call the draw method, specifying the AssistedFreehand object as an argument. The pointer changes to a cross-hair shape when you move it over the image. You can being drawing the ROI. Note how, as you move the pointer, the line you draw follows the edges in the underlying image.

draw(h);

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.
    Finish drawing (close) the ROI.

    Double-click, which adds a vertex at the pointer position and draws a line to the first vertex to close the ROI.

    Right-click, which draws a line from the last vertex to the first vertex.

    Position the pointer over the first vertex and click.

    Press Enter, which draws a line from the last vertex to the first vertex.

    Resize (reshape) the ROI.

    Position pointer over a vertex and then click and drag. No assistance (snapping to edges) is available in this mode.

    Add a vertex (waypoint).

    Position the pointer on an edge of the ROI and double-click.

    Position the pointer on an edge of the ROI, right-click, and select Add Waypoint.

    Remove a vertex (waypoint).

    Position the pointer on a vertex, right-click, and select Remove Waypoint.

    Move the ROI.Position the pointer over the ROI. The pointer changes to the fleur shape. Click and drag to move 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