I don’t understand your code in comment #9. Since some of it is commented out, it looks like you are only applying the rotation matrix, and not the translation ones. Also, applying A1 twice, as you show in one of your commented-out lines, is just translating twice in the same direction. Instead, you need another translation matrix containing the negative of the translation offsets in the first.

%A1= [1 0 0; 0 1 0; 50 0 1];
for i=0:pi/16:2*pi
A2=[cos(i) sin(i) 0; -sin(i) cos(i) 0; 0 0 1];
% A=A1*A2*A1;
A=A2;
B=maketform(‘affine’,A);
rot=imtransform(heli1_512,B,’XData’,[1 512],’YData’,[1 512]);
figure;
imshow(rot);
end

I’d like to know how could I rotate an image not around its center. I’ve been looking on your blog for something related to this question but I cannot find the answer. if it does exist here, please accept my apologize.

thank you in advance,

Michael

Yes you are right, the custom option is for the maketform function. Here is what I have written:

XData = [x_o x_f];
YData = [y_o y_f];
UData = [aax(1) aax(length(aax))];
VData = [rax(1) rax(length(rax))];
size_xy_data = [length(y) length(x)];

frw_fct = [];
inv_fct = @cart2pol;

TFORM = maketform('custom',2,2,frw_fct,inv_fct,[]);

xy_data = imtransform(rp_data,TFORM,'UData',UData,'VData',VData,...
    'XData',XData,'YData',YData,'Size',size_xy_data);

After running I obtain for TFORM:

Error messages edited out. -SLE

I hope this description of my problem is better than the previous one.

Thank you very much,

Maria

I am trying to transform an image in polar coordinates to cartesian coordinates.
I am using imtransform with the ‘custom’ option but I get an error message saying that atan2, in cart2pol.m which is my inverse_function, is not defined for input arguments of type ‘struct’.
I am entering as well UData, VData, XData and YData.

Do you have any suggestions on how to do it with imtransform or any other function?

Thank,

Maria