Polyline region of interest
images.roi.Polyline class creates a polyline region-of-interest
(ROI) object. You call the
draw method of the object to begin drawing the
ROI interactively by using your mouse.
To create a polyline ROI interactively, position the pointer over the axes and click and drag to draw the line. As you draw, click to place vertices along the line. Double-click to finish drawing the polyline. To delete the ROI, position the pointer over the line, right-click, and select Delete Polyline from the context menu. For more information about interactive behaviors including keyboard shortcuts, see Tips.
images.roi.Polyline class is a
creates an instance
h = images.roi.Polyline
images.roi.Polyline class with default properties.
creates the ROI in the axes specified by
h = images.roi.Polyline(
modifies the appearance and behavior of the ROI using one or more name-value pairs to
specify properties. You can set properties using name-value pairs with or without
h = images.roi.Polyline(___,
ax— Parent of ROI
Parent of the ROI, specified as an
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.|
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.|
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
(default) | n-by-2 numeric array
Position of ROI, specified as a n-by-2 array of the form
[x1 y1; x2 y2], where n is the total number of
vertices. Each row specifies the respective end-point of a line segment. You can also
set this property by drawing or moving the line.
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]
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.|
|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 vertex is about to be interactively added to the ROI.|
|A vertex has been interactively added to the ROI.|
|A vertex is about to be interactively deleted from the ROI.|
|A vertex has been interactively deleted from the ROI.|
Read an image into the workspace and display it.
I = imread('baby.jpg'); figure; imshow(I)
Create a polyline ROI on the image, using properties to specify the location of vertices. 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.Polyline 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.Polyline(gca,'Position',[100 150; 200 250; 300 350; 150 450]);
The ROI supports the following interactivity, including keyboard shortcuts.
|Make drawn line snap at 15 degree angles.||Hold the Shift key while drawing.|
|Finish drawing the ROI.|
Double-click, which adds a final new vertex at the pointer position.
Right-click, which adds a final new vertex at the pointer position.
Press Enter, which adds a final new vertex at the pointer position..
|Stop drawing the ROI.||Press Esc. The function returns a valid ROI object with an
|Add a new vertex to the ROI.|
Position the pointer over the polygon and double-click. You can also position the pointer over the ROI, right-click, and choose Add Vertex.
|Remove a vertex from the ROI.|
Position the pointer over the ROI, right-click, and choose Delete Vertex.
|Remove the most recently added vertex but keep drawing.||Press Backspace. The function redraws the line from the previous vertex to the current position of the pointer. You can only back up to the first vertex you drew.|
|Resize (reshape) the ROI.|
Position pointer over a vertex and then click and drag.
Add a new vertex and then click and drag.
Remove a vertex and the shape of the ROI adjusts.
|Move the ROI.||Position the pointer over the line, not on a vertex. The pointer changes to the fleur shape. Click and drag the polygon.|
For information about using an ROI in an app created with App Designer, see Using ROIs in Apps Created with App Designer.