How to create a chessboard?

Question

Alber 2020-2-21

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https://ww2.mathworks.cn/matlabcentral/answers/506787-how-to-create-a-chessboard

评论： Alber 2020-3-9

I have created a chessboard function that goes from values 1 to -1, where its parameters are M (width of the image), N (height), F (rows), C (columns).

My problem is that for certain values of F and C, the function does not respond to me as it should, resulting in something similar to bands instead of squares. I have reviewed the Matlab documentation and have only seen the checkerboard function, which in my case is not worth it. The code of my function is shown below:

function [a] = chessboard3(N,M,C,F)
L1 = floor(M/C);
L2 = floor(N/F);
k = 1;
for m=1:L1:M
    for n=1:L2:N
        a(m:m+L1-1,n:n+L2-1)=ones(L1,L2)*(cos(k*pi));
        k=k+1;
    end
    k=k+1;
end
end

The resolutions that I must prove are:

8k = 7680x4320

4k = 3840x2160

1080p = 1920x1080

Thank you very much in advance.

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Stephen23 2020-2-24

编辑：Stephen23 2020-2-24

在 MATLAB Online 中打开

You don't need loops to generate that chessboard, e.g.:

I = 1-2*kron(toeplitz(mod(1:C,2),mod(1:F,2)),ones(fix(M/C),fix(N/F)))

or use repelem instead of kron.

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Answer 1

Nishant Gupta 2020-2-24

1
链接

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在 MATLAB Online 中打开

I am assuming that you are using plot function to create the chessboard, which is resulting in bands in the output. Instead of it, use imshow function as following :

M = 7680;
N = 4320;
C = 8;
F = 8;
I = chessboard3(N,M,C,F);
imshow(I);  
function [a] = chessboard3(N,M,C,F)
L1 = floor(M/C);
L2 = floor(N/F);
k = 1;
for m=1:L1:M
    for n=1:L2:N
        a(m:m+L1-1,n:n+L2-1)=ones(L1,L2)*(cos(k*pi));
        k=k+1;
    end
    k=k+1;
end
end

Refer following documentation to know more about imshow function: imshow

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Alber 2020-3-9

Thank you very much for your answers, in the end to solve this problem I needed to take into account all cases, for odd and even rows, for even and impart columns for non-whole subdivisions,...

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