imfreehand

Create draggable freehand region

imfreehand is not recommended. Use the new Freehand ROI object instead. You can also use the new ROI creation convenience function drawfreehand. Another option is the AssistedFreehand object, which enables you to hand-draw a shape that automatically follows the edges in the underlying image. For more information, see Compatibility Considerations.

Description

An imfreehand object encapsulates an interactive freehand region over an image.

You can add vertices and adjust the size and position of the polygon by using the mouse. The polygon also has a context menu that controls aspects of its appearance and behavior. For more information, see Usage.

Creation

Description

example

h = imfreehand begins interactive placement of a freehand region on the current axes, and returns an imfreehand object.

h = imfreehand(hparent) begins interactive placement of a freehand region on the object specified by hparent.

h = imfreehand(___,Name,Value) specifies name-value pairs that control the behavior of the freehand region.

Input Arguments

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Handle to parent object, specified as a handle. The parent is typically an axes object, but can also be any other object that can be the parent of an hggroup 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.

Position constraint function, specified as the comma-separated pair consisting of 'PositionConstraintFcn' and a function handle. fcn is called whenever the mouse is dragged. You can use this function to control where the freehand region can be dragged. See the help for the setPositionConstraintFcn function for information about valid function handles.

Freehand region is closed, specified as the comma-separated pair consisting of 'Closed' and true or false. When set to true (the default), imfreehand draws a straight line to connect the endpoints of the freehand line to create a closed region. If set to false, imfreehand leaves the region open.

Data Types: logical

Properties

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ROI can be deleted, specified as true or false.

Data Types: logical

Usage

When you call imfreehand with an interactive syntax, the pointer changes to a cross hairs when positioned over an image. Click and drag the mouse to draw the freehand region and adjust the position of the region. By default, imfreehand draws a straight line connecting the last point you drew with the first point, but you can control this behavior using the Closed parameter.

The freehand region also supports a context menu that you can use to control aspects of its appearance and behavior.

The table lists the interactive features supported by imfreehand.

Interactive BehaviorDescription
Moving the region.Move the pointer inside the freehand region. The pointer changes to a fleur shape . Click and hold the left mouse button to move the region.
Changing the color used to draw the region. Move the pointer inside the freehand region. Right-click and select Set Color from the context menu.
Retrieving the current position of the freehand region. Move the pointer inside the freehand region. Right-click and select Copy Position from the context menu. imfreehand copies an n-by-2 array of coordinates on the boundary of the ROI to the clipboard.
Deleting the regionMove the pointer inside the region. Right-click and select Delete from the context menu. To remove this option from the context menu, set the Deletable property to false: h = imfreehand(); h.Deletable = false;

Object Functions

Each imfreehand object supports a number of methods. Type methods imfreehand to see a complete list.

addNewPositionCallbackAdd new-position callback to ROI object
createMaskCreate mask within image
deleteDelete handle object
getColorGet color used to draw ROI object
getPositionReturn current position of ROI object
getPositionConstraintFcnReturn function handle to current position constraint function
removeNewPositionCallbackRemove new-position callback from ROI object
resume(Not recommended) Resume execution of MATLAB command line
setClosedSet closure behavior of ROI object
setColorSet color used to draw ROI object
setConstrainedPositionSet ROI object to new position
setPositionConstraintFcnSet position constraint function of ROI object
wait(Not recommended) Block MATLAB command line until ROI creation is finished

Examples

Click and Drag to Place Freehand Region

Interactively place a closed freehand region of interest by clicking and dragging over an image.

imshow('pout.tif')
h = imfreehand;   

Interactively move the freehand region by clicking and dragging. Use the wait function to block the MATLAB® command line. Double-click on the freehand region to resume execution of the MATLAB command line.

position = wait(h); 

Tips

  • If you use imfreehand with an axes that contains an image object, and do not specify a position constraint function, users can drag the freehand region outside the extent of the image and lose the freehand region. When used with an axes created by the plot function, the axes limits automatically expand to accommodate the movement of the freehand region.

  • To cancel the interactive placement, press the Esc key. imfreehand returns an empty object.

Compatibility Considerations

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Not recommended starting in R2018b

Introduced in R2007b