Create freehand ROI on image with assistance from image edges
h = drawassisted
h = drawassisted(hImage)
h = drawassisted(___,Name,Value)
begins interactive placement
of a freehand region-of-interest (ROI) on the current axes. The
h = drawassisted
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.
To create an ROI interactively, position the pointer on the image, click and release to place the first vertex (waypoint), and then move the pointer to draw a line. The line snaps to nearby edges in the image automatically as you draw. Click to place vertices along the line as you draw. To finish the ROI and close the shape, double-click. To delete an ROI, position the pointer on the ROI (not on a vertex), right-click, and select Delete Freehand from the context menu. For more information about keyboard shortcuts, see Tips.
Read an image into the workspace and display it.
im = imread('peppers.png'); imshow(im)
Draw an assisted freehand ROI.
h = drawassisted;
Create a mask of the ROI.
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);
Display a target image.
target = imread('fabric.png'); imshow(target)
Resize the source image and the alpha matrix to the same size as the target image.
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)
hImage— Image object on which to draw ROI
Image object on which to draw ROI, specified as an image object.
comma-separated pairs of
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
h = drawassisted('LineWidth',5);
'Closed'— Close freehand ROI
Close the freehand ROI, specified the comma-separated pair consisting of
'Closed' and the logical value
drawassisted closes the ROI by connecting the last waypoint drawn
to the first waypoint drawn.
'Color'— ROI color
ROI color, specified as the comma-separated pair consisting of
ColorSpec (Color Specification)
[0 1 0]
'Deletable'— ROI can be interactively deleted via context menu
ROI can be interactively deleted via a context menu, specified as the comma-separated
pair consisting of
'Deletable' and a logical value of
false. When the value is
true (default), you can delete the ROI via the context menu. To
disable this context menu item, set
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.
'FaceAlpha'— Transparency of ROI face
0.2(default) | scalar
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
'FaceSelectable'— ROI face can capture clicks
ROI face can capture clicks, specified as the comma-separated pair consisting of
'FaceSelectable' and the value
true (default), the ROI face can
capture clicks. When
false, the ROI face cannot capture
'HandleVisibility'— Visibility of ROI handle in
Childrenproperty of parent
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
|The object handle is always visible (default).|
|The object handle is hidden at all times.|
|The object handle is visible from within callbacks or functions invoked by callbacks, but not from within functions invoked from the command line.|
'Image'— Image on which to draw ROI
Image on which to draw ROI, specified as the comma-separated pair consisting of
'Image' and a handle to an
'InteractionsAllowed'— Interactivity of ROI
Interactivity of the ROI, specified as the comma-separated
pair consisting of
'InteractionsAllowed' and one
of the values in this table.
|The ROI is fully interactable (default).|
|The ROI is not interactable, and no drag points are visible.|
|ROI can be translated (moved) within the
drawing area but not reshaped. This value is not
available with the |
|ROI can be reshaped within the drawing area
but not translated. This value is not available
with the |
'Label'— ROI label
''(default) | character vector | string
ROI label, specified as the comma-separated pair consisting of
a character vector or string. By default, this property is set to an empty array
'') and the ROI has no label.
'LineWidth'— Width of ROI edge
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.
'Parent'— ROI parent
ROI parent, specified as the comma-separated pair consisting of
Axes object. A
UIAxes cannot be the parent
of the ROI.
'Position'— Position of 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.
'Selected'— Selection state of ROI
Selection state of the ROI, specified as the comma-separated pair
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
'SelectedColor'— Color of ROI when selected
'none'(default) | colorspec
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
Color defines the color of the ROI for all states,
selected or not.
[0 1 0]
'Smoothing'— Smooth edge of freehand ROI
1(default) | nonnegative scalar
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.
'StripeColor'— Color of ROI stripe
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
[0 1 0]
'Tag'— Tag to associate with ROI
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
'UIContextMenu'— Context menu
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
uicontextmenu function and then configuring context menu
'UserData'— Data to associate with ROI
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.
'Visible'— ROI visibility
ROI visibility, specified as the comma-separated pair consisting of
'Visible' and one of the values in this table.
|Specify this value to display the ROI (default).|
|Specify this value to hide the ROI without deleting it. You still can access the properties of an invisible ROI.|
'Waypoints'— Control points to reshape the ROI
1(default) | n-by-1 logical vector
Control points to reshape the ROI, specified as the comma-separated pair
'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
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.
The ROI supports the following interactivity, including keyboard shortcuts.
|Stop drawing the ROI.||Press Esc. The function returns a valid ROI object with an
|Finish drawing (close) the ROI.|
Double-click, which adds a vertex at the pointer position and draws a line to the first vertex to close the ROI.
Right-click, which draws a line from the last vertex to the first vertex.
Position pointer over the first vertex and click.
Press Enter, which draws a line from the last vertex to the first vertex.
|Resize (reshape) the ROI.|
Position pointer over a vertex and then click and drag. No assistance (snapping to edges) is available in this mode.
|Add a vertex (waypoint).|
Position the pointer on an edge of the ROI and double-click.
Position the pointer on an edge of the ROI, right-click, and select Add Waypoint.
|Remove a vertex (waypoint).|
Position the pointer on a vertex, 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.|