# moving an image across the screen along some vector path

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Kendall Donahoe on 6 Apr 2021
Answered: LO on 6 Apr 2021
hey Ive been trying to move an image of the avatar across the screen and can't seem to figure it out. I know how to shift the image using the identity matrix and was wondering if there was a way I could use that to make it move across the screen or any other way that it is possible. Here are some of the function names I have been using and the way that I shifted it. I have attached the image and a converter script that I used.
A= imread('avatar.jpg');
Aout=Jpeg2pointsConverter(A, 15);
plot(Aout(1,:), Aout(2,:),'b.')
[nrows, ncols]=size(Aout);
AA=[Aout; ones(1,ncols)];
S=eye(3)
>> S(1,3)=300
>> A3=S*AA;
>> hold on, plot(A3(1,:), A3(2,:),'r.')
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DGM on 6 Apr 2021
Edited: DGM on 6 Apr 2021
I have no idea what you're trying to do with this, but this whole thing
BB1=BB(:,:,1);
[M, N]= size(BB1);
BB1=double(BB1);
BB2 = 255-BB1; %Invert so white is 0 instead of 255
BB3 = (BB2 > THRESHOLD); %Any point with high value is replaced by 1, and
%any point with a low value is replaced by 0
PP=zeros(2,M*N);
cnt=0;
for ii=1:M,
for jj=1:N,
if (BB3(ii,jj)>0.5),
% this is going to return nonsense indices
% once you change the aspect ratio
PP(:,cnt+1)=[jj;N-ii];
cnt=cnt+1;
end,
end,
end
PPout = PP(:,1:cnt);
can be replaced with this
[rows cols]=find(BB(:,:,1)<(255-threshold));
PPout=[cols; rows];
I don't know why you're returning all the row indices backwards, but i guess you could still do that
[rows cols]=find(BB(:,:,1)<(255-threshold));
PPout=[cols; size(BB,1)-rows];

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### Answers (1)

LO on 6 Apr 2021
try using circshift
https://de.mathworks.com/help/matlab/ref/circshift.html
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