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drawpolyline

Create customizable polyline ROI

Syntax

h = drawpolyline
h = drawpolyline(ax,___)
h = drawpolyline(___,Name,Value)

Description

example

h = drawpolyline begins interactive placement of a polyline region-of-interest (ROI) on the current axes. The function returns a handle to a images.roi.Polyline object. You can modify the ROI interactively using your mouse. The ROI object also supports a context menu that controls aspects of its appearance and behavior.

h = drawpolyline(ax,___) begins interactive placement of an instance of the ROI in the axes specified by ax.

h = 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.

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.

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]);

Input Arguments

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Parent axes of the ROI, specified as an axes object.

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: h = 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. This value is not available with the drawPoint function.
'reshape'ROI can be reshaped within the drawing area but not translated. This value is not available with the drawPoint function and the drawRectangle function.

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.

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 object. A UIAxes cannot be the parent of the ROI.

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 using the findobj function.

Context menu, specified as the comma-separated pair consisting of 'UIContextMenu' and a uicontextmenu object. Specify this name-value pair to display a custom context menu when you right-click on 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 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 an invisible ROI.

Output Arguments

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Polyline ROI, returned as an images.roi.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..

    Stop 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.

Introduced in R2018b