# making a transformation of an already moving image

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Kendall Donahoe on 12 Mar 2021
Edited: Prabhan Purwar on 19 Mar 2021
I need to make it so that the leter k is transformed once per rotation as the letter moves and can't figure out how to do it. please help I have attached my script
% This script will move the letter K about the screen using
% homogeneous coordinate transformations common to computer graphics
p1=[0;0]; p2=[0.5;0]; p3=[0.5;4]; p4=[3;0]; p5=[3.5;0]; p6=[0.5;4]; p7=[3;8]; p8=[2.5;8]; p9=[0.5;4];p10=[0.5;8]; p11=[0;8];
D = [p1,p2,p3,p4,p5,p6,p7,p8,p9,p10,p11]
fill(D(1,:),D(2,:),'r')
axis([-30 30 -30 30])
hold on
N = [D;ones(1,11)]
N1=N;
R = [cos(pi/18) -sin(pi/18) 0; sin(pi/18) cos(pi/18) 0; 0 0 1]
color = str2mat('y','m','c','r','g','b','k');
for i=0:5
Shift = [1 0 i; 0 1 i; 0 0 1];
N1 = Shift*N1;
for j=1:36
N1 = R*N1;
D1 = N1(1:2,:);
fill(D1(1,:),D1(2,:),color(rem(j,7)+1))
pause(0.15);
end
end
hold off

Prabhan Purwar on 19 Mar 2021
Edited: Prabhan Purwar on 19 Mar 2021
Hi,
To make the letter k transform once per rotation you will need to change from letter coordinate frame to global coordinate frame where the circular path is defined.
Kindly have a look at the following code:
p1=[0;0]; p2=[0.5;0]; p3=[0.5;4]; p4=[3;0]; p5=[3.5;0]; p6=[0.5;4]; p7=[3;8]; p8=[2.5;8]; p9=[0.5;4];p10=[0.5;8]; p11=[0;8];
D = [p1,p2,p3,p4,p5,p6,p7,p8,p9,p10,p11];
fill(D(1,:),D(2,:),'r')
axis([-30 30 -30 30])
hold on
N = [D;ones(1,11)];
N1=N;
R = [cos(pi/18) -sin(pi/18) 0; sin(pi/18) cos(pi/18) 0; 0 0 1];
color = char('y','m','c','r','g','b','k');
for i=0:5
% Shift = [1 0 i; 0 1 i; 0 0 1];
% N1 = Shift*N1;
N1 = R*N1;
D1 = N1(1:2,:);
for j=1:36
x = (3*i+3)*cosd(10*j);
y = (3*i+3)*sind(10*j);
% Transform to global coordinate frame
fill(D1(1,:)+x,D1(2,:)+y,color(rem(j,7)+1))
pause(0.15);
end
end
hold off
Thanks