Radon transform of a circle. Error in imread function

Hi everyone,

This is my code to radon transform a circle:

   A = imread('circ3.png');
    theta = 0:180;
    [R,xp] = radon(A,theta);
    imshow(R,[],'Xdata',theta,'Ydata',xp,'InitialMagnification','fit')
    xlabel('\theta (degrees)')
    ylabel('x''')
    colormap(gca,hot), colorbar

However I am getting this error when I run my code:

Error in radon (line 63)

validateattributes(I,{'numeric','logical'},{'2d','nonsparse'},mfilename,'I',1);

Error in Untitled9 (line 3)

[R,xp] = radon(A,theta);

The image circ3.png is saved on my PC and imshow(A) works perfectly fine. I also tried the code with A=imread('circlesbrightdark.png.') and the code runs fine. But the image circlesbrightdark.png isnt saved on my PC? So where is the code reading the image from?

Answer 1

[Walter Roberson]

You cannot apply radon() to an RGB image. Look at ndims(A) to see whether it is 2 (2D) or 3 (RGB or RGBA)

Note that some RGB images look grayscale, because they happen to have equal R G and B.