drawpolyline

Create customizable polyline ROI

Description

example

roi = drawpolyline creates a Polyline ROI object and enables interactive drawing of a polyline 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 to draw vertices of the polyline and drag to draw the lines between the vertices. To finish the ROI, double-click the mouse button. For more information about using the ROI, including keyboard shortcuts and context menu options, see Tips.

Note

drawpolyline is a convenience function for creating an Polyline ROI object. If you create the ROI object directly, calling Polyline, you must call the draw object function to enable interactive drawing of the ROI. In contrast, the drawpolyline 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 = drawpolyline(ax,___) creates the ROI in the axes specified by ax.

roi = drawpolyline(___,Name,Value) modifies the appearance and behavior of the ROI using one or more name-value pairs. Unspecified name-value pairs are set to the default value.

Examples

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Read an image into the workspace and display it.

imshow(imread('westconcordaerial.png'))

Draw the polyline ROI on the image. Use the 'Color' name-value pair to specify the color of the line.

h = drawpolyline('Color','green');

Decrease the width of the edge of the ROI by setting the 'LineWidth' property.

h.LineWidth = 1;

Read image into the workspace and display it.

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

Draw a polygonal ROI over the image, using named parameters to specify the location and shape. The example also specifies that the edge of the polygon is a striped.

h = drawpolyline('Position',[500 500;400 600;400 700;500 800;600 800;700 700; 700 600]);

Read an image into the workspace.

I = imread('cameraman.tif'); 

Display the image.

imshow(I);

Draw a Polyline ROI on the image.

roi = drawpolyline('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

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Parent axes of the ROI, specified as an Axes object or a UIAxes object. For information about using an ROI in a UIAxes, including important limitations, see Using ROIs in Apps Created with App Designer.

Name-Value Pair Arguments

Specify optional comma-separated pairs of Name,Value arguments. Name is the argument name and Value is the corresponding value. Name must appear inside quotes. You can specify several name and value pair arguments in any order as Name1,Value1,...,NameN,ValueN.

Example: roi = drawpolyline('LineWidth',1);

ROI color, specified as the comma-separated pair consisting of 'Color' and a MATLAB® ColorSpec (Color Specification) value.

Example: 'green'

Example: 'g'

Example: [0 1 0]

ROI can be interactively deleted via a context menu, specified as the comma-separated pair consisting of 'Deletable' and a logical value of 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 'Deletable' 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 the comma-separated pair consisting of 'DrawingArea' and 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 rectangle beginning at (x,y), with width w and height h.

Visibility of the ROI handle in the Children property of the parent, specified as the comma-separated pair consisting of 'HandleVisibility' and 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 the comma-separated pair consisting of 'InteractionsAllowed' and 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'ROI can be translated (moved) within the drawing area but not reshaped.
'reshape'ROI can be reshaped within the drawing area but not translated.

ROI label, specified as the comma-separated pair consisting of 'Label' and a character vector or string. By default, this property is set to an empty array ('') and the ROI has no label.

Visibility of the ROI label, specified as the comma-separated pair consisting of 'LabelVisible' and one of these values.

ValueDescription
'on'Label is visible when the ROI is visible, and the Label property is nonempty (default).
'hover'

Label is visible only when the mouse hovers over the ROI.

'off'Label is not visible.

Width of the ROI edge, specified as the comma-separated pair consisting of 'LineWidth' and a positive numeric scalar in points. The default value is three times the number of points per screen pixel.

ROI parent, specified as the comma-separated pair consisting of 'Parent' and an Axes or UIAxes object. For information about using an ROI in a UIAxes, including important limitations, see Using ROIs in Apps Created with App Designer.

Position of the polyline ROI, specified as the comma-separated pair consisting of 'Position' and an n-by-2 array, of the form [x1 y1; …; xn yn], where n represents the number of vertices. Each row specifies the position of a vertex of the polyline ROI.

Selection state of the ROI, specified as the comma-separated pair consisting of 'Selected' and true or false. You can also set this value interactively. For example, clicking the ROI selects it and sets this value to true. Similarly, if you Ctrl-click the ROI, deselects it and sets this value to false.

Color of the ROI when selected, specified as the comma-separated pair consisting of 'SelectedColor' and a MATLAB ColorSpec (Color Specification). 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 the comma-separated pair consisting of 'StripeColor' and a MATLAB ColorSpec (Color Specification) value. 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 the comma-separated pair consisting of 'Tag' and a character vector or string scalar. Use the tag value to find the ROI object in a hierarchy of objects by using the findobj function.

Context menu, specified as the comma-separated pair consisting of 'UIContextMenu' and a ContextMenu object creating using the uicontextmenu function. Specify this name-value pair to display a custom context menu when you right-click the ROI. To create a custom context menu, create a ContextMenu object, by using the uicontextmenu function, and then configure context menu properties.

Data to associate with the ROI, specified as the comma-separated pair consisting of 'UserData' and 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 the comma-separated pair consisting of 'Visible' and one of the values in this table.

ValueDescription
'on'Specify this value to display the ROI (default).
'off'Specify this value to hide the ROI without deleting it. You still can access the properties of a hidden ROI.

Output Arguments

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Polyline ROI, returned as an Polyline object.

Tips

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

    BehaviorKeyboard shortcut
    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..

    Cancel drawing the ROI.Press Esc. The function returns a valid ROI object with an empty Position field.
    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 ROI.
    Delete the ROI. Position the pointer anywhere on the ROI and right-click. Select Delete Polyline from the context menu. You can also delete the ROI using the delete object function.
  • The drawpolyline function returns a Polyline ROI 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 roi to yellow, set its Color property, 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 wait object 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 addlistener object 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 Polyline object, see Set Up Listener for Polyline ROI Events. For more details about these capabilities, see the Polyline object documentation.

Introduced in R2018b