用matlab编程实现彩色图片中正方形的检测

实现彩色图片中正方形的检测，可以采用以下步骤：

1. 读入彩色图片并进行灰度化处理。

img = imread('color_image.jpg');
gray_img = rgb2gray(img);

2. 对灰度图像进行边缘检测，可以使用Canny算子或Sobel算子等。

edge_img = edge(gray_img, 'Canny');

3. 对边缘图像进行霍夫变换，检测直线。

[H, T, R] = hough(edge_img);
P = houghpeaks(H, 50);
lines = houghlines(edge_img, T, R, P);

4. 根据直线的交点，计算出所有可能的正方形，并进行筛选。

for i = 1:length(lines)-1
    for j = i+1:length(lines)
        x1 = lines(i).point1(1);
        y1 = lines(i).point1(2);
        x2 = lines(i).point2(1);
        y2 = lines(i).point2(2);
        x3 = lines(j).point1(1);
        y3 = lines(j).point1(2);
        x4 = lines(j).point2(1);
        y4 = lines(j).point2(2);
        if abs(atan2(y2-y1, x2-x1) - atan2(y4-y3, x4-x3)) < 0.1
            x5 = (x1+x2+x3+x4)/4;
            y5 = (y1+y2+y3+y4)/4;
            if abs(sqrt((x1-x5)^2 + (y1-y5)^2) - sqrt((x2-x5)^2 + (y2-y5)^2)) < 10 && abs(sqrt((x1-x5)^2 + (y1-y5)^2) - sqrt((x3-x5)^2 + (y3-y5)^2)) < 10
                square = [x1, y1, x2, y2, x3, y3, x4, y4];
                squares = [squares; square];
            end
        end
    end
end

其中，筛选的条件是：两条直线的夹角小于0.1弧度，且四边的长度差异小于10个像素。

5. 在原图上绘制出所有检测到的正方形。

figure, imshow(img), hold on
for i = 1:size(squares, 1)
    x = squares(i, [1,3,5,7,1]);
    y = squares(i, [2,4,6,8,2]);
    plot(x, y, 'LineWidth', 2, 'Color', 'r');
end
hold off

绘制出来的正方形可能不够精确，需要根据具体情况进行调整。

完整代码如下：

img = imread('color_image.jpg');
gray_img = rgb2gray(img);
edge_img = edge(gray_img, 'Canny');
[H, T, R] = hough(edge_img);
P = houghpeaks(H, 50);
lines = houghlines(edge_img, T, R, P);

squares = [];
for i = 1:length(lines)-1
    for j = i+1:length(lines)
        x1 = lines(i).point1(1);
        y1 = lines(i).point1(2);
        x2 = lines(i).point2(1);
        y2 = lines(i).point2(2);
        x3 = lines(j).point1(1);
        y3 = lines(j).point1(2);
        x4 = lines(j).point2(1);
        y4 = lines(j).point2(2);
        if abs(atan2(y2-y1, x2-x1) - atan2(y4-y3, x4-x3)) < 0.1
            x5 = (x1+x2+x3+x4)/4;
            y5 = (y1+y2+y3+y4)/4;
            if abs(sqrt((x1-x5)^2 + (y1-y5)^2) - sqrt((x2-x5)^2 + (y2-y5)^2)) < 10 && abs(sqrt((x1-x5)^2 + (y1-y5)^2) - sqrt((x3-x5)^2 + (y3-y5)^2)) < 10
                square = [x1, y1, x2, y2, x3, y3, x4, y4];
                squares = [squares; square];
            end
        end
    end
end

figure, imshow(img), hold on
for i = 1:size(squares, 1)
    x = squares(i, [1,3,5,7,1]);
    y = squares(i, [2,4,6,8,2]);
    plot(x, y, 'LineWidth', 2, 'Color', 'r');
end
hold off