MATLAB：在黑白图像上画一条线

Question

如果已知起点和终点坐标，在MATLAB中在黑白（二进制）图像上绘制线条的最佳方法是什么？

请注意，我不是要添加注释行。我希望这条线成为图像的一部分。

Answer 1

您可能需要my answer查看有关adding a line to an image matrix的SO问题。这是一个类似于我在该答案中的示例，它将从行和列索引(10, 10)到(240, 120)生成一条白线：

img = imread('cameraman.tif');  % Load a sample black and white image
x = [10 240];                   % x coordinates
y = [10 120];                   % y coordinates
nPoints = max(abs(diff(x)), abs(diff(y)))+1;    % Number of points in line
rIndex = round(linspace(y(1), y(2), nPoints));  % Row indices
cIndex = round(linspace(x(1), x(2), nPoints));  % Column indices
index = sub2ind(size(img), rIndex, cIndex);     % Linear indices
img(index) = 255;  % Set the line points to white
imshow(img);       % Display the image

这是最终的图像：

Answer 2

如果您对其他方法的特殊情况感到困扰，这里的防弹方法会产生一条线：

• 其像素在整个行长期间始终相互接触（像素彼此相邻8个像素），
• 线的密度不依赖于附加参数，但是可灵活确定以适应第一点的保证。

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输入（方便用这段代码制作功能）：

• img - 包含图片的矩阵
• x1，y1，x2，y2 - 要绘制的行的终点坐标。

代码：

% distances according to both axes
xn = abs(x2-x1);
yn = abs(y2-y1);

% interpolate against axis with greater distance between points;
% this guarantees statement in the under the first point!
if (xn > yn)
    xc = x1 : sign(x2-x1) : x2;
    yc = round( interp1([x1 x2], [y1 y2], xc, 'linear') );
else
    yc = y1 : sign(y2-y1) : y2;
    xc = round( interp1([y1 y2], [x1 x2], yc, 'linear') );
end

% 2-D indexes of line are saved in (xc, yc), and
% 1-D indexes are calculated here:
ind = sub2ind( size(img), yc, xc );

% draw line on the image (change value of '255' to one that you need)
img(ind) = 255;

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以下是在其上绘制三条线的示例图像：

Answer 3

This algorithm提供了一种方法。

Answer 4

这实际上只是对plesiv的答案的修改。我在图像上画了数千行，我需要提高性能。省略interp1调用和使用整数变量所做的最大改进使它稍微快一些。与plesiv的代码相比，它在我的电脑上的速度提高了大约18％。

function img = drawLine(img, x1, y1, x2, y2)
x1=int16(x1); x2=int16(x2); y1=int16(y1); y2=int16(y2);
% distances according to both axes
xn = double(x2-x1);
yn = double(y2-y1);

% interpolate against axis with greater distance between points;
% this guarantees statement in the under the first point!
if (abs(xn) > abs(yn))
    xc = x1 : sign(xn) : x2;
    if yn==0
        yc = y1+zeros(1, abs(xn)+1, 'int16');
    else
    yc = int16(double(y1):abs(yn/xn)*sign(yn):double(y2));
    end
else
    yc = y1 : sign(yn) : y2;
    if xn==0
        xc = x1+zeros(1, abs(yn)+1, 'int16');
    else
    xc = int16(double(x1):abs(xn/yn)*sign(xn):double(x2));
    end
end

% 2-D indexes of line are saved in (xc, yc), and
% 1-D indexes are calculated here:
ind = sub2ind(size(img), yc, xc);

% draw line on the image (change value of '255' to one that you need)
img(ind) = 255;
end

Answer 5

如果您有计算机视觉系统工具箱，则可以使用insertShape。