How to create a checkerboard image without using the inbuilt function?

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Deep P
Deep P 2016-6-6
编辑： DGM 2023-2-20
Hello All,
I wanted to create a checkerboard image(1280x960) where each color(balck or white) is 16x16 in dimension. I do not want to use inbuilt function. Please help me on this.
Thanks.

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Stephen23
Stephen23 2016-6-6
编辑：Stephen23 2016-6-6
Here is one way without using any toolbox functions, or any slow (and ugly) loops:
>> imgSiz = [16,12];
>> blkSiz = [4,4];
>> numRep = imgSiz./blkSiz;
>> basMat = toeplitz(mod(0:numRep(1)-1,2),mod(0:numRep(2)-1,2));
>> outImg = repelem(basMat,[blkSiz,3])
outImg =
0 0 0 0 1 1 1 1 0 0 0 0
0 0 0 0 1 1 1 1 0 0 0 0
0 0 0 0 1 1 1 1 0 0 0 0
0 0 0 0 1 1 1 1 0 0 0 0
1 1 1 1 0 0 0 0 1 1 1 1
1 1 1 1 0 0 0 0 1 1 1 1
1 1 1 1 0 0 0 0 1 1 1 1
1 1 1 1 0 0 0 0 1 1 1 1
0 0 0 0 1 1 1 1 0 0 0 0
0 0 0 0 1 1 1 1 0 0 0 0
0 0 0 0 1 1 1 1 0 0 0 0
0 0 0 0 1 1 1 1 0 0 0 0
1 1 1 1 0 0 0 0 1 1 1 1
1 1 1 1 0 0 0 0 1 1 1 1
1 1 1 1 0 0 0 0 1 1 1 1
1 1 1 1 0 0 0 0 1 1 1 1
This makes a simple binary image. Obviously you need to replicate along the third dimension if you need an RGB image.
If you don't have repelem, then this FEX submission also does the job: http://www.mathworks.com/matlabcentral/fileexchange/24536-expand

更多回答（3 个）

DGM
DGM 2023-2-20
编辑：DGM 2023-2-20
Ran in:
How about using only mod(), xor(), and basic operators (colon, transpose, relational)?
% parameters
squaresize = [20 20]; % the size of squares [y x]
sizeout = [200 200]; % the image size [y x]
% create a checkerboard mask
xx = mod(0:(sizeout(2)-1),squaresize(2)*2) < squaresize(2);
yy = mod(0:(sizeout(1)-1),squaresize(1)*2) < squaresize(1);
mask = xor(xx,yy');
% display it
imshow(mask)
Okay, I guess I did use imshow(), but that's not necessary to "create" the image.
I guess I'm also relying on implicit array expansion, so if I were to answer this in early 2016, I'd have to use bsxfun() or repmat().
% generalized expansion was introduced in R2016b
mask = bsxfun(@xor,xx,yy'); % works back to R2007a
Maybe that reduces the value a bit.
While this example is more complicated than simple blockwise replication using a single 2x2 checkerboard block and repmat(), it does allow the image size to be independent of the square size without adding extra steps. This makes it simple to generalize further without the introduction of new concepts.
% parameters
squaresize = [4 4]; % the size of squares [y x]
sizeout = [20 25]; % the image size [y x]
offset = [2 2]; % offset from the NW corner [y x]
% create a checkerboard mask
xx = offset(2):(sizeout(2) + offset(2) - 1);
yy = offset(1):(sizeout(1) + offset(1) - 1);
xx = mod(xx,squaresize(2)*2) < squaresize(2);
yy = mod(yy,squaresize(1)*2) < squaresize(1);
mask = xor(xx,yy');
% display it
imshow(mask)
See also:
https://www.mathworks.com/matlabcentral/answers/274850-how-to-create-color-checkerboard-any-size#answer_1107543
John BG
John BG 2016-6-7
编辑：John BG 2016-7-25
Deep P
this works, no inbuilt functions:
sx=1280;sy=960;
bas=16 % length base square side
% assume sx and sy are multiples of base
Lx=(-1).^[1:1:sx/bas];
Ly=(-1).^[1:1:sy/bas];
A=ones(sx,sy);
[Ai Aj]=ind2sub([sx sy],[1:1:sx*sy]);
Ai2=reshape(Ai,[sx sy]);
Aj2=reshape(Aj,[sx sy]);
linex=[1:bas:sx];linex=[linex sx];
liney=[1:bas:sy];liney=[liney sy];
setx=zeros(1,bas);
for k=2:1:(length(linex)-1)
L1=[linex(k-1):1:(linex(k)-1)]
setx=[setx;L1];
end
setx(1,:)=[];
sety=zeros(1,bas);
for k=2:1:length(liney)-1
L2=[liney(k-1):1:liney(k)-1];
sety=[sety;L2];
end
sety(1,:)=[];
blk=ones(bas,bas);
for k=1:1:sx/bas-1
for s=1:1:sy/bas-1
Lx1=blk*Lx(k);
Ly1=blk*Ly(s);
L12=Lx1.*Ly1;
A(setx(k,:),sety(s,:))=A(setx(k,:),sety(s,:)).*L12;
end;
end;
check the result with the marker on
imshow(A)
If you find this answer of any help solving your question,
please click on the thumbs-up vote link, or mark this answer as accepted
thanks in advance
John
jgb2012@sky.com
  1 个评论
TEGENE Garedew
TEGENE Garedew 2019-11-23
thanks that is nice but it doesn't display 8 squares only 7 squares and a white region on the left and bottom region

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Nipuna
Nipuna 2020-9-7
Following function worked
call the function binerycheckerboard(1280,960)
function a = binerycheckerboard(n,y)
b = ones(n,y);
for i=0:n-1
for a=0:y-1
c = rem(i,16);
d = fix(i/16);
e = rem(d,2);
f = rem(a,16);
g = fix(a/16);
h = rem(g,2);
if e == 0 && h == 0 || e ~= 0 && h ~= 0
b(i+1,a+1) = 1;
else
b(i+1,a+1) = 0;
end
end
end
imshow(b)
imtool(b)

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