peaks = houghpeaks(H,numpeaks) locates
peaks in the Hough transform matrix, H, generated
by the hough function. numpeaks specifies
the maximum number of peaks to identify. The function returns peaks a
matrix that holds the row and column coordinates of the peaks.

peaks = houghpeaks(H,numpeaks,Name,Value)
controls aspects of the operation using name-value pair arguments.

Find peaks in the Hough transform of the image and plot them.

P = houghpeaks(H,2);
imshow(H,[],'XData',T,'YData',R,'InitialMagnification','fit');
xlabel('\theta'), ylabel('\rho');
axis on, axis normal, hold on;
plot(T(P(:,2)),R(P(:,1)),'s','color','white');

Hough transform matrix, specified as a numeric array. The rows and columns correspond to
rho and theta values. Use the
hough function to create a
Hough transform matrix.

Data Types: double

numpeaks — Maximum number of peaks to identify 1 (default) | positive integer

Maximum number of peaks to identify, specified as a positive integer.

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: P = houghpeaks(H,2,'Threshold',15);

'Threshold' — Minimum value to be considered a peak 0.5*max(H(:)) (default) | nonnegative number

Minimum value to be considered a peak, specified as a nonnegative
number.

Data Types: double

'NHoodSize' — Size of suppression neighborhood 2-element vector of positive odd integers

Size of the suppression neighborhood, specified as a 2-element vector
of positive odd integers. The suppression
neighborhood is the neighborhood around each peak that
is set to zero after the peak is identified. The default value of
NHoodSize is the smallest odd values greater
than or equal to size(H)/50. The dimensions of
NHoodSize must be smaller than the size of the
Hough transform matrix, H.

Hough transform theta values, specified as a numeric vector returned
by the hough function. Each element of the vector
specifies the theta value for the corresponding
column of the output matrix H.
houghpeaks uses the theta
values specified for peak suppression. Use the hough function to
create a Hough transform matrix.

Note

If you specify the 'Theta' parameter as input
to the hough function, you must specify the
theta parameter with the
houghpeaks function. Use the
theta output value from the
hough function as the
theta input value for
houghpeaks. Otherwise, peak suppression can
result in unexpected results.

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