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Hough Transform

这Image Processing Toolbox™ supports functions that enable you to use the Hough transform to detect lines in an image.

这houghfunction implements the Standard Hough Transform (SHT). The Hough transform is designed to detect lines, using the parametric representation of a line:

ρ= x*cos(theta) + y*sin(theta)

这variableρis the distance from the origin to the line along a vector perpendicular to the line.theta是X轴和该向量之间的角度。这houghfunction generates a parameter space matrix whose rows and columns correspond to theseρ和thetavalues, respectively.

After you compute the Hough transform, you can use thehoughpeaksfunction to find peak values in the parameter space. These peaks represent potential lines in the input image.

After you identify the peaks in the Hough transform, you can use thehoughlinesfunction to find the endpoints of the line segments corresponding to peaks in the Hough transform. This function automatically fills in small gaps in the line segments.

Detect Lines in Images Using Hough

Open Live Script

This example shows how to detect lines in an image using the Houghtransform.

在工作区中读取图像，并使此示例更具说明性，请旋转图像。显示图像。

I = imread('电路.tif'); rotI = imrotate(I,33,'庄稼'); imshow(rotI)

Figure contains an axes object. The axes object contains an object of type image.

使用图像中的边缘edgefunction.

BW = edge(rotI,'canny'); imshow(BW);

Figure contains an axes object. The axes object contains an object of type image.

Compute the Hough transform of the binary image returned byedge.

[H,theta,rho] = hough(BW);

Display the transform,H, returned by thehoughfunction.

figure imshow(imadjust(rescale(H)),[],...“XData”,theta,...'YData',rho,...'InitialMagnification','fit'); xlabel('\theta (degrees)'）ylabel（'\rho') axis上axisnormalhold上colormap(gca,hot)

Figure contains an axes object. The axes object contains an object of type image.

Find the peaks in the Hough transform matrix,H, using thehoughpeaksfunction.

P = houghpeaks(H,5,'threshold',ceil(0.3*max(H(:))));

Superimpose a plot on the image of the transform that identifies the peaks.

x = theta(P(:,2)); y = rho(P(:,1)); plot(x,y,'s','color','black');

Figure contains an axes object. The axes object contains 2 objects of type image, line.

Find lines in the image using thehoughlinesfunction.

lines = houghlines(BW,theta,rho,P,'FillGap'，5，'MinLength'，7）;

Create a plot that displays the original image with the lines superimposed on it.

figure, imshow(rotI), hold上max_len = 0;fork = 1:length(lines) xy = [lines(k).point1; lines(k).point2]; plot(xy(:,1),xy(:,2),'LineWidth',2,'Color','green');% Plot beginnings and ends of linesplot(xy(1,1),xy(1,2),'x','LineWidth',2,'Color','yellow'); plot(xy(2,1),xy(2,2),'x','LineWidth',2,'Color',“红色”);% Determine the endpoints of the longest line segmentlen = norm(lines(k).point1 - lines(k).point2);if( len > max_len) max_len = len; xy_long = xy;endend% highlight the longest line segmentplot(xy_long(:,1),xy_long(:,2),'LineWidth',2,'Color',“红色”);

Figure contains an axes object. The axes object contains 38 objects of type image, line.