# How the number of times n of the patchwork increase?

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John schwan on 29 Aug 2021
Commented: John schwan on 4 Sep 2021
clc;
rnd_x = randperm(size(A,1)-128,7);%choose 7 random unique points on x-axis
rnd_y = randperm(size(A,2)-128,7);%choose 7 random unique points on y-axis
image(A)
for ii = 1:4
for jj = 5:7
piece{jj} = A((rnd_x(jj):(rnd_x(jj)+127)),(rnd_y(jj):(rnd_y(jj)+127)),1:3)+1;
A((rnd_x(jj):(rnd_x(jj)+127)),(rnd_y(jj):(rnd_y(jj)+127)),1:3)= piece{jj}; % add the changed pixel values to the original image A
end
piece{ii} = A((rnd_x(ii):(rnd_x(ii)+127)),(rnd_y(ii):(rnd_y(ii)+127)),1:3)-1;%Convert chosen numbers to image pieces
A((rnd_x(ii):(rnd_x(ii)+127)),(rnd_y(ii):(rnd_y(ii)+127)),1:3)= piece{ii}; % add the changed pixel values to the original image A
end
imshow(A)
The above is my coding running good but it give me the following error."Error using randperm K must be less than or equal to N.
Error in file (line 3)
rnd_x = randperm(size(A,1)-128,6000);%choose 7 random unique points on x-axis"
when I want to choose 6000 or 4000 random unique points on x-axis or y-axis in the place of 7 like the following code:
clc;
rnd_x = randperm(size(A,1)-128,6000);%choose 7 random unique points on x-axis
rnd_y = randperm(size(A,2)-128,6000);%choose 7 random unique points on y-axis
image(A)
for ii = 1:3000
for jj = 3001:6000
piece{jj} = A((rnd_x(jj):(rnd_x(jj)+127)),(rnd_y(jj):(rnd_y(jj)+127)),1:3000)+1;
A((rnd_x(jj):(rnd_x(jj)+127)),(rnd_y(jj):(rnd_y(jj)+127)),1:3000)= piece{jj}; % add the changed pixel values to the original image A
end
piece{ii} = A((rnd_x(ii):(rnd_x(ii)+127)),(rnd_y(ii):(rnd_y(ii)+127)),1:3000)-1;%Convert chosen numbers to image pieces
A((rnd_x(ii):(rnd_x(ii)+127)),(rnd_y(ii):(rnd_y(ii)+127)),1:3000)= piece{ii}; % add the changed pixel values to the original image A
end
imshow(A)
I actually need help in the number of times n of the patchwork increase from 7 up to 6000.

Rik on 29 Aug 2021
You don't check if your image is actually large enough to allow 6000 unique indices. You should either reduce the number of samples in such a case, or increase the resolution of your image.
John schwan on 4 Sep 2021
Thank you very much. I will search them all. I hope to find a solution.

R2015a

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