drawfreehand

Create customizable freehand ROI

Syntax

h = drawfreehand

h = drawfreehand(ax)

h = drawfreehand(___,Name=Value)

Description

The drawfreehand function creates a Freehand object that specifies the shape and position of a freehand region of interest (ROI). You can create the ROI interactively by drawing the ROI over an image using the mouse, or programmatically by using name-value arguments. You can also specify the initial appearance and behavior of the ROI.

Freehand ROI tracing the edge of an object in an image.

After you create the ROI, you can use object properties, object functions, and event notifications to customize the shape, position, appearance, and behavior of the ROI. For more information about using these capabilities, see Tips.

h = drawfreehand creates a Freehand object and enables interactive drawing of a circular 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 and drag to draw the line. To finish the ROI, release the mouse button. For more information about using the ROI, including keyboard shortcuts and context menu options, see Tips.

example

h = drawfreehand(ax) creates the ROI in the axes specified by ax.

h = drawfreehand(___,Name=Value) modifies the appearance and behavior of the ROI using one or more name-value arguments.

Examples

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Create Freehand ROI That Is Not Selectable

Open Live Script

Read an image into the workspace and display it.

imshow(imread('yellowlily.jpg'))

Draw a freehand ROI.

h = drawfreehand;

Fill in the face of the freehand ROI and disable the ability to select the ROI. The ROI does not move when you click and drag the mouse.

h.FaceAlpha = 1;
h.FaceSelectable = false;

Set Up Listener for Freehand ROI Events

Open Live Script

Read an image into the workspace.

I = imread('cameraman.tif');

Display the image.

imshow(I);

Draw a freehand ROI on the image.

roi = drawfreehand('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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`ax` — Parent of ROI
`gca` (default) | `Axes` object | `UIAxes` object

Parent of 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 Arguments

Specify optional pairs of arguments as Name1=Value1,...,NameN=ValueN, where Name is the argument name and Value is the corresponding value. Name-value arguments must appear after other arguments, but the order of the pairs does not matter.

Example: h = drawfreehand(Color="y") creates a yellow colored Freehand object.

Before R2021a, use commas to separate each name and value, and enclose Name in quotes.

Example: h = drawfreehand("Color","y") creates a yellow colored Freehand object.

`Closed` — Close freehand ROI
`true` or `1` (default) | `false` or `0`

Close the freehand ROI, specified as a numeric or logical 1 (true) or 0 (false). When true, the drawfreehand function closes the ROI by connecting the last waypoint drawn to the first waypoint drawn.

`Color` — ROI color
`[0 0.4470 0.7410]` (default) | RGB triplet | color name | short color name

ROI color, specified as an RGB triplet, a color name, or a short color name.

You can specify any color using an RGB triplet. An RGB triplet is a 3-element row vector whose elements specify the intensities of the red, green, and blue components of the color. The intensities must be in the range [0, 1].

You can specify some common colors by name as a string scalar or character vector. This table lists the named color options and the equivalent RGB triplets.

Color Name	Short Name	RGB Triplet
`"red"`	`"r"`	`[1 0 0]`
`"green"`	`"g"`	`[0 1 0]`
`"blue"`	`"b"`	`[0 0 1]`
`"cyan"`	`"c"`	`[0 1 1]`
`"magenta"`	`"m"`	`[1 0 1]`
`"yellow"`	`"y"`	`[1 1 0]`
`"black"`	`"k"`	`[0 0 0]`
`"white"`	`"w"`	`[1 1 1]`

Here are the RGB triplets for the default colors that MATLAB^® uses in many types of plots.

RGB Triplet	Appearance
`[0 0.4470 0.7410]`
`[0.8500 0.3250 0.0980]`
`[0.9290 0.6940 0.1250]`
`[0.4940 0.1840 0.5560]`
`[0.4660 0.6740 0.1880]`
`[0.3010 0.7450 0.9330]`
`[0.6350 0.0780 0.1840]`

Example: "Color","r"

Example: "Color","green"

Example: "Color",[0 0.4470 0.7410]

`ContextMenu` — Context menu
`ContextMenu` object

Context menu that displays when you right-click the ROI, specified as a ContextMenu object. You can create a custom context menu by using the uicontextmenu function and then configuring context menu properties.

`Deletable` — Context menu provides option to delete the ROI
`true` or `1` (default) | `false` or `0`

Context menu provides an option to delete the ROI, specified as a numeric or logical 1 (true) or 0 (false). When the value is true, you can delete the ROI interactively using the context menu. When the value is false, the context menu option to delete the ROI is disabled.

In both cases, you can delete the ROI outside of the context menu by using the delete function.

`DrawingArea` — Area of axes in which you can interactively place ROI
`"auto"` (default) | `"unlimited"` | `[x,y,w,h]`

Area of the axes in which you can interactively place the ROI, specified as one of the values in this table.

Value	Description
`"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.

`FaceAlpha` — Transparency of ROI face
`0.2` (default) | number in the range [0, 1]

Transparency of the ROI face, specified as a number in the range [0, 1]. When the value is 1, the ROI face is completely opaque. When the value is 0, the ROI face is completely transparent.

`FaceSelectable` — ROI face can capture clicks
`true` or `1` (default) | `false` or `0`

ROI face can capture clicks, specified as a numeric or logical 1 (true) or 0 (false). When true, the ROI face captures mouse clicks. When false, the ROI face does not capture mouse clicks.

`HandleVisibility` — Visibility of ROI handle in `Children` property of parent
`"on"` (default) | `"off"` | `"callback"`

Visibility of the ROI handle in the Children property of the parent, specified as one of the values in this table.

Value	Description
`"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.

`InteractionsAllowed` — Interactivity of ROI
`"all"` (default) | `"none"` | `"reshape"` | `"translate"`

Interactivity of the ROI, specified as one of the values in this table.

Value	Description
`"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.
`"reshape"`	The ROI can be reshaped but not translated.

`Label` — ROI label
`''` (default) | character vector | string scalar

ROI label, specified as a character vector or string scalar. By default, the ROI has no label ('').

`LabelAlpha` — Transparency of text background
`1` (default) | number in the range [0, 1]

Transparency of the text background, specified as a number in the range [0, 1]. When set to 1, the text background is completely opaque. When set to 0, the text background is completely transparent.

`LabelTextColor` — Label text color
`"black"` (default) | RGB triplet | color name | short color name

Label text color, specified as an RGB triplet, a color name, or a short color name.

You can specify some common colors by name as a string scalar or character vector. This table lists the named color options and the equivalent RGB triplets.

Color Name	Short Name	RGB Triplet
`"red"`	`"r"`	`[1 0 0]`
`"green"`	`"g"`	`[0 1 0]`
`"blue"`	`"b"`	`[0 0 1]`
`"cyan"`	`"c"`	`[0 1 1]`
`"magenta"`	`"m"`	`[1 0 1]`
`"yellow"`	`"y"`	`[1 1 0]`
`"black"`	`"k"`	`[0 0 0]`
`"white"`	`"w"`	`[1 1 1]`

Here are the RGB triplets for the default colors that MATLAB uses in many types of plots.

RGB Triplet	Appearance
`[0 0.4470 0.7410]`
`[0.8500 0.3250 0.0980]`
`[0.9290 0.6940 0.1250]`
`[0.4940 0.1840 0.5560]`
`[0.4660 0.6740 0.1880]`
`[0.3010 0.7450 0.9330]`
`[0.6350 0.0780 0.1840]`

Example: "LabelTextColor","r"

Example: "LabelTextColor","green"

Example: "LabelTextColor",[0 0.4470 0.7410]

`LabelVisible` — Label visibility
`"on"` (default) | `"off"` | `"hover"`

Label visibility, specified as one of these values.

Value	Description
`"on"`	Label is visible when the ROI is visible.
`"hover"`	Label is visible only when the mouse is hovering over the ROI.
`"off"`	Label is not visible.

`LineWidth` — Width of ROI border
positive number

Width of the ROI border, specified as a positive number in points. The default value is three times the number of points per screen pixel, such that the border is three pixels wide.

`MarkerSize` — Marker size
positive number

Marker size, specified as a positive number in points. The default value is eight times the number of points per screen pixel, such that markers are eight pixels in size.

`Multiclick` — Control freehand drawing style during interactive placement
`false` or `0` (default) | `true` or `1`

Control the freehand drawing style during interactive placement, specified as a numeric or logical 0 (false) or 1 (true). When the value is false, a single click and drag gesture completes the freehand ROI. When the value is true, multiple click and drag gestures can be combined with straight edges to make a more complex freehand ROI shape.

`Parent` — ROI parent
`Axes` object | `UIAxes` object

ROI parent, specified as 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` — Position of ROI
n-by-2 numeric matrix

Position of the ROI, specified as an n-by-2 numeric matrix where n is the number of vertices or points defining the ROI. Each row represents the [x y] coordinates of a vertex or point.

`Selected` — Selection state of ROI
`false` or `0` (default) | `true` or `1`

Selection state of the ROI, specified as a numeric or logical 0 (false) or 1 (true).

`SelectedColor` — Color of ROI when selected
`"none"` (default) | RGB triplet | color name | short color name

Color of the ROI when selected, specified as an RGB triplet, a color name, a short color name, or "none". If you specify "none", then the value of Color defines the color of the ROI for all states, selected or not.

You can specify some common colors by name as a string scalar or character vector. This table lists the named color options and the equivalent RGB triplets.

Color Name	Short Name	RGB Triplet
`"red"`	`"r"`	`[1 0 0]`
`"green"`	`"g"`	`[0 1 0]`
`"blue"`	`"b"`	`[0 0 1]`
`"cyan"`	`"c"`	`[0 1 1]`
`"magenta"`	`"m"`	`[1 0 1]`
`"yellow"`	`"y"`	`[1 1 0]`
`"black"`	`"k"`	`[0 0 0]`
`"white"`	`"w"`	`[1 1 1]`

Here are the RGB triplets for the default colors that MATLAB uses in many types of plots.

RGB Triplet	Appearance
`[0 0.4470 0.7410]`
`[0.8500 0.3250 0.0980]`
`[0.9290 0.6940 0.1250]`
`[0.4940 0.1840 0.5560]`
`[0.4660 0.6740 0.1880]`
`[0.3010 0.7450 0.9330]`
`[0.6350 0.0780 0.1840]`

Example: "SelectedColor","r"

Example: "SelectedColor","green"

Example: "SelectedColor",[0 0.4470 0.7410]

`Smoothing` — Smoothing applied to edge of ROI
`1` (default) | nonnegative number

Smoothing applied to the edge of the ROI after interactive placement, specified as a nonnegative number. The drawfreehand function filters the x and y coordinates of the ROI using a Gaussian smoothing kernel with a default standard deviation of 1. The size of the Gaussian filter is 2*ceil(2*Smoothing)+1. You can see the smoothing effect only after completing the drawing.

`StripeColor` — Color of ROI stripe
`"none"` (default) | RGB triplet | color name | short color name

Color of the ROI stripe, specified as an RGB triplet, a color name, a short color name, or "none". If you specify "none", then the ROI edge is a solid color specified by Color. Otherwise, the edge of the ROI is striped, with colors alternating between the colors specified by Color and StripeColor.

You can specify some common colors by name as a string scalar or character vector. This table lists the named color options and the equivalent RGB triplets.

Color Name	Short Name	RGB Triplet
`"red"`	`"r"`	`[1 0 0]`
`"green"`	`"g"`	`[0 1 0]`
`"blue"`	`"b"`	`[0 0 1]`
`"cyan"`	`"c"`	`[0 1 1]`
`"magenta"`	`"m"`	`[1 0 1]`
`"yellow"`	`"y"`	`[1 1 0]`
`"black"`	`"k"`	`[0 0 0]`
`"white"`	`"w"`	`[1 1 1]`

Here are the RGB triplets for the default colors that MATLAB uses in many types of plots.

RGB Triplet	Appearance
`[0 0.4470 0.7410]`
`[0.8500 0.3250 0.0980]`
`[0.9290 0.6940 0.1250]`
`[0.4940 0.1840 0.5560]`
`[0.4660 0.6740 0.1880]`
`[0.3010 0.7450 0.9330]`
`[0.6350 0.0780 0.1840]`

Example: "StripeColor","r"

Example: "StripeColor","green"

Example: "StripeColor",[0 0.4470 0.7410]

`Tag` — Tag to associate with ROI
`''` (default) | character vector | string scalar

Tag to associate with the ROI, specified as a character vector or string scalar. Use the tag value to find the ROI object in a hierarchy of objects using the findobj function.

`UserData` — Data to associate with ROI
any MATLAB data

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. The drawfreehand object does not use this data.

`Visible` — ROI visibility
`"on"` (default) | `"off"` | on/off logical value

ROI visibility, specified as "on" or "off", or as a numeric or logical 1 (true) or 0 (false). A value of "on" is equivalent to true, and "off" is equivalent to false. The value is stored as an on/off logical value of type OnOffSwitchState.

Value	Description
`"on"`	Display the ROI.
`"off"`	Hide the ROI without deleting it. You still can access the properties of an invisible ROI.

`Waypoints` — Position point is waypoint
n-by-1 logical vector

Position point is waypoint, specified as an n-by-1 logical vector where n is the number of points defining the ROI. The length of Waypoints must match the number of rows of the Position name-value argument. Elements in Waypoints with the value true identify points in the Position matrix that are waypoints.

Waypoints appear as circular shapes on the ROI edge. You can use waypoints to reshape the ROI by clicking and dragging the waypoint with the mouse. Moving waypoints modifies the freehand-drawn region between the waypoint that you clicked and the adjacent waypoints.

Output Arguments

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`h` — Freehand ROI
`Freehand` object

Freehand ROI, returned as an Freehand object.

Tips

The ROI supports the following interactivity, including keyboard shortcuts.

Behavior	Keyboard shortcut
Cancel drawing the ROI.	Press Esc. The function returns a valid ROI object with an empty `Position` property.
Finish drawing (close) the ROI.	Double-click, which adds a point at the pointer position and draws a line connecting this point to the first point drawn, closing the ROI. Right-click, which draws a line connecting the last point to the first point drawn. Position the pointer over the first point and click. Press Enter, which draws a line connecting the last point to the first point drawn.
Resize (reshape) the ROI.	Position pointer over a waypoint and then click and drag. No assistance (snapping to edges) is available in this mode.
Add a waypoint.	Position the pointer on an edge of the ROI, right-click, and select Add Waypoint. You can also position the pointer on an edge of the ROI and double-click.
Remove a waypoint.	Position the pointer on a waypoint, 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.
Delete an ROI.	Position the pointer on the ROI (not on a vertex), right-click, and select Delete Freehand from the context menu. You can also delete the ROI programmatically using the `delete` function.

The drawfreehand function creates a Freehand object. After you create the object, you can modify the shape, position, appearance, and behavior of the ROI by using these object capabilities.

Capability Support

Object properties

Capability	Support
Object properties	ROI objects have properties that specify their shape, position, appearance, and behavior. After you create the ROI object, change properties using dot notation. For example, to change the color of the `roi` to yellow, set its `Color` property: roi.Color = 'yellow'
Object functions	ROI objects have object functions that operate on the ROIs. For example, if you want to pause the MATLAB command line after creating an ROI, use the `wait` function.
Event notifications	ROI objects can notify your code when certain events occur, such as when the ROI is clicked or when the ROI is being moved. To receive event notifications, set up listeners. 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. You can specify a callback function that executes when an event occurs.

ROI objects have properties that specify their shape, position, appearance, and behavior. After you create the ROI object, change properties using dot notation.

For example, to change the color of the roi to yellow, set its Color property:

roi.Color = 'yellow'

Object functions ROI objects have object functions that operate on the ROIs. For example, if you want to pause the MATLAB command line after creating an ROI, use the wait function.

Event notifications

ROI objects can notify your code when certain events occur, such as when the ROI is clicked or when the ROI is being moved. To receive event notifications, set up listeners. 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. You can specify a callback function that executes when an event occurs.

For an example of using event listeners with the Freehand object, see Set Up Listener for Freehand ROI Events.

Version History

Introduced in R2018b

expand all

R2020a: `UIContextMenu` name-value argument is not recommended

Starting in R2020a, using the UIContextMenu name-value argument to assign a context menu to an ROI object is not recommended. Use the ContextMenu name-value argument instead. The values are the same.

There are no plans to remove support for the UIContextMenu name-value argument at this time.

drawfreehand

Syntax

Description

Examples

Create Freehand ROI That Is Not Selectable

Set Up Listener for Freehand ROI Events

Input Arguments

ax — Parent of ROI gca (default) | Axes object | UIAxes object

Name-Value Arguments

Closed — Close freehand ROI true or 1 (default) | false or 0

Color — ROI color [0 0.4470 0.7410] (default) | RGB triplet | color name | short color name

ContextMenu — Context menu ContextMenu object

Deletable — Context menu provides option to delete the ROI true or 1 (default) | false or 0

DrawingArea — Area of axes in which you can interactively place ROI "auto" (default) | "unlimited" | [x,y,w,h]

FaceAlpha — Transparency of ROI face 0.2 (default) | number in the range [0, 1]

FaceSelectable — ROI face can capture clicks true or 1 (default) | false or 0

HandleVisibility — Visibility of ROI handle in Children property of parent "on" (default) | "off" | "callback"

InteractionsAllowed — Interactivity of ROI "all" (default) | "none" | "reshape" | "translate"

Label — ROI label '' (default) | character vector | string scalar

LabelAlpha — Transparency of text background 1 (default) | number in the range [0, 1]

LabelTextColor — Label text color "black" (default) | RGB triplet | color name | short color name

LabelVisible — Label visibility "on" (default) | "off" | "hover"

LineWidth — Width of ROI border positive number

MarkerSize — Marker size positive number

Multiclick — Control freehand drawing style during interactive placement false or 0 (default) | true or 1

Parent — ROI parent Axes object | UIAxes object

Position — Position of ROI n-by-2 numeric matrix

Selected — Selection state of ROI false or 0 (default) | true or 1

SelectedColor — Color of ROI when selected "none" (default) | RGB triplet | color name | short color name

Smoothing — Smoothing applied to edge of ROI 1 (default) | nonnegative number

StripeColor — Color of ROI stripe "none" (default) | RGB triplet | color name | short color name

Tag — Tag to associate with ROI '' (default) | character vector | string scalar

UserData — Data to associate with ROI any MATLAB data

Visible — ROI visibility "on" (default) | "off" | on/off logical value

Waypoints — Position point is waypoint n-by-1 logical vector

Output Arguments

h — Freehand ROI Freehand object

Tips

Version History

R2020a: UIContextMenu name-value argument is not recommended

See Also

Topics

`ax` — Parent of ROI
`gca` (default) | `Axes` object | `UIAxes` object

`Closed` — Close freehand ROI
`true` or `1` (default) | `false` or `0`

`Color` — ROI color
`[0 0.4470 0.7410]` (default) | RGB triplet | color name | short color name

`ContextMenu` — Context menu
`ContextMenu` object

`Deletable` — Context menu provides option to delete the ROI
`true` or `1` (default) | `false` or `0`

`DrawingArea` — Area of axes in which you can interactively place ROI
`"auto"` (default) | `"unlimited"` | `[x,y,w,h]`

`FaceAlpha` — Transparency of ROI face
`0.2` (default) | number in the range [0, 1]

`FaceSelectable` — ROI face can capture clicks
`true` or `1` (default) | `false` or `0`

`HandleVisibility` — Visibility of ROI handle in `Children` property of parent
`"on"` (default) | `"off"` | `"callback"`

`InteractionsAllowed` — Interactivity of ROI
`"all"` (default) | `"none"` | `"reshape"` | `"translate"`

`Label` — ROI label
`''` (default) | character vector | string scalar

`LabelAlpha` — Transparency of text background
`1` (default) | number in the range [0, 1]

`LabelTextColor` — Label text color
`"black"` (default) | RGB triplet | color name | short color name

`LabelVisible` — Label visibility
`"on"` (default) | `"off"` | `"hover"`

`LineWidth` — Width of ROI border
positive number

`MarkerSize` — Marker size
positive number

`Multiclick` — Control freehand drawing style during interactive placement
`false` or `0` (default) | `true` or `1`

`Parent` — ROI parent
`Axes` object | `UIAxes` object

`Position` — Position of ROI
n-by-2 numeric matrix

`Selected` — Selection state of ROI
`false` or `0` (default) | `true` or `1`

`SelectedColor` — Color of ROI when selected
`"none"` (default) | RGB triplet | color name | short color name

`Smoothing` — Smoothing applied to edge of ROI
`1` (default) | nonnegative number

`StripeColor` — Color of ROI stripe
`"none"` (default) | RGB triplet | color name | short color name

`Tag` — Tag to associate with ROI
`''` (default) | character vector | string scalar

`UserData` — Data to associate with ROI
any MATLAB data

`Visible` — ROI visibility
`"on"` (default) | `"off"` | on/off logical value

`Waypoints` — Position point is waypoint
n-by-1 logical vector

`h` — Freehand ROI
`Freehand` object

R2020a: `UIContextMenu` name-value argument is not recommended