viscircles

Create circle

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Syntax

viscircles(centers,radii)
viscircles(ax,centers,radii)
viscircles(___,Name,Value)
h = viscircles(___)

Description

example

viscircles(centers,radii) draws circles with specified centers and radii onto the current axes.

viscircles(ax,centers,radii) draws circles onto the axes specified by ax.

viscircles(___,Name,Value) uses name-value pair arguments to specify additional properties of the circles.

h = viscircles(___) returns a handle, h, to the drawn circles.

Examples

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Open Live Script

Read the image into the workspace and display it.

A = imread('circlesBrightDark.png');
imshow(A)

Define the radius range.

Rmin = 30;
Rmax = 65;

Find all the bright circles in the image within the radius range.

[centersBright, radiiBright] = imfindcircles(A,[Rmin Rmax],'ObjectPolarity','bright');

Find all the dark circles in the image within the radius range.

[centersDark, radiiDark] = imfindcircles(A,[Rmin Rmax],'ObjectPolarity','dark');

Draw blue lines around the edges of the bright circles.

viscircles(centersBright, radiiBright,'Color','b');

Draw red dashed lines around the edges of the dark circles.

viscircles(centersDark, radiiDark,'LineStyle','--');

Open Live Script

The viscircles function does not clear the target axes before plotting circles. To remove circles that have been previously plotted in an axes, use the cla function. To illustrate, this example creates a new figure and then loops, drawing a set of circles with each iteration, clearing the axes each time.

figure
colors = {'b','r','g','y','k'}; 
 
for k = 1:5
    % Create 5 random circles to display,
    X = rand(5,1);
    Y = rand(5,1);
    centers = [X Y];
    radii = 0.1*rand(5,1);
 
    % Clear the axes.
    cla
 
    % Fix the axis limits.
    xlim([-0.1 1.1])
    ylim([-0.1 1.1])
 
    % Set the axis aspect ratio to 1:1.
    axis square
 
    % Set a title.
    title(['k = ' num2str(k)])
 
    % Display the circles.
    viscircles(centers,radii,'Color',colors{k});
              
    % Pause for 1 second.
    pause(1)
end

Input Arguments

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Coordinates of circle centers, specified as a P-by-2 matrix, such as that obtained from imfindcircles. The x-coordinates of the circle centers are in the first column and the y-coordinates are in the second column. The coordinates can be integers (of any numeric type) or floating-point values (of type double or single).

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

Circle radii, specified as a column vector such as that returned by imfindcircles. The radius value at radii(j) corresponds to the circle with center coordinates centers(j,:). The values of radii can be nonnegative integers (of any numeric type) or floating-point values (of type double or single).

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

Axes in which to draw circles, specified as a handle object returned by gca or axes.

Data Types: double

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: viscircles(centers,radii,'Color','b') specifies blue circle edges, using the short color name for blue.

Augment drawn circles with contrasting features to improve visibility, specified as a logical value true or false. If you set the value to true, then viscircles draws a contrasting circle below the colored circle.

Data Types: logical

Color of the boundary, specified as an RGB triplet, a hexadecimal color code, a color name, or a short color name.

For a custom color, specify an RGB triplet or a hexadecimal color code.

  • An RGB triplet is a three-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]; for example, [0.4 0.6 0.7].

  • A hexadecimal color code is a character vector or a string scalar that starts with a hash symbol (#) followed by three or six hexadecimal digits, which can range from 0 to F. The values are not case sensitive. Thus, the color codes '#FF8800', '#ff8800', '#F80', and '#f80' are equivalent.

Alternatively, you can specify some common colors by name. This table lists the named color options, the equivalent RGB triplets, and hexadecimal color codes.

Color NameShort NameRGB TripletHexadecimal Color CodeAppearance
'red''r'[1 0 0]'#FF0000'

'green''g'[0 1 0]'#00FF00'

'blue''b'[0 0 1]'#0000FF'

'cyan' 'c'[0 1 1]'#00FFFF'

'magenta''m'[1 0 1]'#FF00FF'

'yellow''y'[1 1 0]'#FFFF00'

'black''k'[0 0 0]'#000000'

'white''w'[1 1 1]'#FFFFFF'

'none'Not applicableNot applicableNot applicableNo color

Here are the RGB triplets and hexadecimal color codes for the default colors MATLAB® uses in many types of plots.

RGB TripletHexadecimal Color CodeAppearance
[0 0.4470 0.7410]'#0072BD'

[0.8500 0.3250 0.0980]'#D95319'

[0.9290 0.6940 0.1250]'#EDB120'

[0.4940 0.1840 0.5560]'#7E2F8E'

[0.4660 0.6740 0.1880]'#77AC30'

[0.3010 0.7450 0.9330]'#4DBEEE'

[0.6350 0.0780 0.1840]'#A2142F'

Example: viscircles(centers,radii,'Color','r');

Example: viscircles(centers,radii,'Color','green');

Example: viscircles(centers,radii,'Color',[0 0 1]);

Example: viscircles(centers,radii,'Color','#FF8800');

Line style of circle edge, specified as the comma-separated pair consisting of 'LineStyle' and any line specifier in the table below.

Line StyleDescriptionResulting Line
'-'Solid line

'--'Dashed line

':'Dotted line

'-.'Dash-dotted line

'none'No lineNo line

Width of circle edge, specified a positive number. Line width is expressed in points, where each point equals 1/72 of an inch.

Data Types: double

Output Arguments

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Circles drawn, returned as an hggroup object. h is the child of the axes ax if specified, otherwise h is the child of the current axes.

See Also

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Introduced in R2012a

Image Processing Toolbox Documentation

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