Assisted freehand region of interest
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.
images.roi.AssistedFreehand class is a
instance of the
h = images.roi.AssistedFreehand
images.roi.AssistedFreehand class with default
creates the ROI on the axes specified by
h = images.roi.AssistedFreehand(
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
h = images.roi.AssistedFreehand(___,
ax— Parent of ROI
Parent of the ROI, specified as an
Closed— Close freehand ROI
Close the freehand ROI, specified as a logical value
images.roi.Freehand closes the ROI by connecting the last point
drawn to the first point drawn.
Color— ROI color
ROI color, specified as a MATLAB®
[0 1 0]
Deletable— ROI can be interactively deleted via context menu
ROI can be interactively deleted via a context menu, specified as
false. When the value is
true (default), you
can delete the ROI via the context menu. To disable this context menu item, set this
false. When the value is set to
you can still delete the ROI by calling the
specifying the handle to the ROI as the input.
DrawingArea— Area of axes in which you can interactively place ROI
Area of the axes in which you can interactively place the ROI, specified as one of the values in this table.
|The drawing area is the current axes limits (default).|
|The drawing area has no boundary and ROIs can be drawn or dragged to extend beyond the axes limits.|
|The drawing area is restricted to a rectangular region beginning at (x,y), and extending to width w and height h.|
FaceAlpha— Transparency of ROI face
0.2(default) | numeric scalar
Transparency of the ROI face, specified as a numeric scalar value in the range
1]. When the value is
1, the ROI face is fully opaque.
When the value is
0, the ROI face is completely transparent.
FaceSelectable— ROI face can capture clicks
ROI face can capture clicks, specified as
true (default), the ROI face
captures mouse clicks. When
false, the ROI face does not capture
HandleVisibility— Visibility of ROI handle in
Childrenproperty of parent
Visibility of the ROI handle in the
Children property of the parent,
specified as one of the values in this table.
|The object handle is always visible (default).|
|The object handle is hidden at all times.|
|The object handle is visible from within callbacks or functions invoked by callbacks, but not from within functions invoked from the command line.|
Image— Image on which to draw ROI
Image on which to draw ROI, specified as a handle to an
InteractionsAllowed— Interactivity of ROI
Interactivity of the ROI, specified as one of the values in this table.
|The ROI is fully interactable (default).|
|The ROI is not interactable, and no drag points are visible.|
|The ROI can be translated (moved) within the drawing area but not
reshaped. This value is not available for use with
|The ROI can be reshaped but not translated. This value is not
available for use with |
Label— ROI label
''(default) | character vector | string
ROI label, specified as a character vector or string. By default, the ROI has no label
LineWidth— Width of ROI edge
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.
Parent— ROI parent
ROI parent, specified as an
Axes object. A
be the parent of the ROI.
Position— Position of ROI
Position of the ROI, specified as an n-by-2 numeric array of
[x1 y1;...;xn yn], where n is the total
number of vertices. Each row specifies the position of a point on the ROI edge.
Selected— Selection state of ROI
Selection state of the ROI, specified as the logical value
false. You can also set this property interactively. For example,
clicking on the ROI selects the ROI and sets this property to
Similarly, pressing the Ctrl key and clicking the ROI deselects the ROI
and sets the value of this property to
SelectedColor— Color of ROI when selected
Color of the ROI when selected, specified as a MATLAB
ColorSpec (Color Specification). The
intensities must be in the range
'SelectedColor' is set to
'none', then the
Color defines the color of the ROI for all states,
selected or not.
[0 1 0]
Smoothing— Smooth edge of freehand ROI
1(default) | nonnegative numeric scalar
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.
StripeColor— Color of ROI stripe
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
[0 1 0]
Tag— Tag to associate with the ROI
''(default) | character vector | string scalar
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
UIContextMenu— Context menu
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.
UserData— Data to associate with ROI
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.
Visible— ROI visibility
ROI visibility, specified as one of the values in this table.
|Display the ROI (default).|
|Hide the ROI without deleting it. You still can access the properties of an invisible ROI.|
Waypoints— Control points to reshape freehand ROI
(default) | n-by-1 logical vector
Control points to reshape the freehand ROI, specified as an
n-by-1 logical vector, the same length as
Position. Each element of the
vector indicates if the corresponding point in the
is a waypoint. Positions that are waypoints are set to
Waypoints. Dragging a waypoint modifies the ROI between the
specified waypoint and its immediate neighboring waypoints. When you draw the freehand
images.roi.AssistedFreehand automatically generates
Waypoints at locations of increased curvature.
|Event Name||Trigger||Event Data||Event Attributes|
|ROI is about to be interactively deleted.|
|ROI is about to be interactively drawn.|
|ROI has been interactively drawn.|
|ROI shape or location is being interactively changed.|
|ROI shape or location has been interactively changed.|
|ROI has been clicked.|
|A waypoint is about to be interactively added to the ROI.|
|A waypoint has been interactively added to the ROI.|
|A waypoint is about to be interactively removed from the ROI.|
|A waypoint has been interactively removed from the ROI.|
Read an image into the workspace and display it.
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
h = images.roi.AssistedFreehand;
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
The ROI supports the following interactivity, including keyboard shortcuts.
|Stop drawing the ROI.||Press Esc. The function returns a valid ROI object with an
|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.