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drawassisted

Create freehand ROI on image with assistance from image edges

Syntax

h = drawassisted
h = drawassisted(hImage)
h = drawassisted(___,Name,Value)

Description

h = drawassisted begins interactive placement of a freehand region-of-interest (ROI) on the current axes. The drawassisted function uses the edges in the underlying image to "assist" the drawing process. The function returns h, a handle to an images.roi.AssistedFreehand object. You can modify the ROI interactively using your mouse. The ROI also supports a right-click context menu that controls aspects of its appearance and behavior.

h = drawassisted(hImage) begins interactive placement of a freehand ROI on the image specified by hImage.

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

During interactive placement, click and release to place the first waypoint. A live segment of the freehand boundary follows the mouse cursor, snapping to nearby edges in the image. Waypoints are placed automatically at regular intervals, or by a manual left-click. To delete the last waypoint, use the Backspace key. To override the assisted segment, click and drag it. To close the region, double-click, right-click or click the first waypoint. To reshape the freehand region after the shape has been drawn, click the waypoints . No assistance is available in this mode.

You add additional waypoints after drawing via the context menu or by double-clicking on the edge of the freehand ROI. Remove a waypoint by right-clicking on that waypoint and selecting Remove Waypoint from the context menu.

Examples

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Read an image into the workspace and display it.

figure
im = imread('peppers.png');
imshow(im)

Draw an assisted freehand ROI.

h = drawassisted();

Create a mask of the ROI you drew.

bw = createMask(h);

Create an alpha matrix that specifies the transparency of the source image at each pixel.

alphamat = imguidedfilter(single(bw),im,'DegreeOfSmoothing',2);

Obtain a target image, and resize the source image and the alpha matrix.

target = imread('fabric.png');
alphamat = imresize(alphamat,[size(target,1),size(target,2)]);
im = imresize(im, [size(target,1), size(target,2)]);

Alpha blend the source ROI into the target image.

fused = single(im).*alphamat + (1-alphamat).*single(target);
fused = uint8(fused);
imshow(fused)

Input Arguments

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Image object on which to draw ROI, specified as an image 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 = drawassisted('LineWidth',5);

Close the freehand ROI, specified the comma-separated pair consisting of 'Closed' and the logical value true or false. If true (default), drawassisted closes the ROI by connecting the last waypoint drawn to the first waypoint drawn.

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.

Transparency of ROI face, specified as the comma-separated pair consisting of 'FaceAlpha' and a scalar value in the range [0,1]. When the value is 1, the ROI face is fully opaque. When the value is 0, the ROI face is completely transparent.

ROI face can capture clicks, specified as the comma-separated pair consisting of 'FaceSelectable' and the value true or false. When true (default), the ROI face can capture clicks. When false, the ROI face cannot capture clicks.

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.

Image on which to draw ROI, specified as the comma-separated pair consisting of 'Image' and a handle to an Image object.

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 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 is the number of vertices in the ROI. Each row specifies the position of a vertex in the 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]

Smooth the edge of the freehand ROI using the standard deviation of the Gaussian smoothing kernel, specified as the comma-separated pair consisting of 'Smoothing' and a nonnegative scalar. The function uses this 'Smoothing' value to filter the x and y coordinates of the freehand ROI. The function defines the filter size as 2*ceil(2*Smoothing) + 1.

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.

Control points to reshape the ROI, specified as the comma-separated pair consisting of 'Waypoints' and an n-by-1 logical vector, the same length as Position. Each element of the Waypoints vector indicates if the corresponding point in the Position array is a waypoint. Positions that are waypoints are set to true in Waypoints. Dragging a waypoint modifies the ROI between the specified waypoint and its immediate neighboring waypoints. If empty, drawfreehand automatically generates Waypoints at locations of increased curvature.

Output Arguments

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Assisted Freehand ROI, returned as an images.roi.AssistedFreehand object.

Introduced in R2018b