[Scilab-users] Radon transform

[Tan Chin Luh]

Hi,

If you are using the Scilab 6, you can consider using IPCV "imradon" 
function.

another implementation in scilab code attached in this email, radon.sci. 
This is pretty slow as it is using a for loop if you were to plot from 
0:179 degree.  this function will need nan toolbox.

hope this helps.

rgds,
CL





On 15/11/2017 8:01 PM, Jean-Philippe Grivet wrote:
> Hello,
>
> Does an implementation of the Radon transform exist in Scilab, similar 
> to the Matlab
> "radon" function ? Would anybody be willing to share a homemade version ?
>
> Thank you for your input
> JP Grivet
>
>
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-------------- next part --------------
function [RT,Xp] = radon(I,theta)
     [m, n] = size (I);
    //pause
    // center of image
    xc = floor ((m+1)/2);
    yc = floor ((n+1)/2);

    // divide each pixel into 2x2 subpixels

    d = matrix (I,[1 m 1 n]);
    d = d([1 1],:,[1 1],:);
    d = matrix (d,[2*m 2*n])/4;

    b = ceil (sqrt (sum (size (I).^2))/2 + 1);
    xp = [-b:b]';
    sz = size(xp);

    [X,Y] = ndgrid (0.75 - xc + [0:2*m-1]/2,0.75 - yc + [0:2*n-1]/2);

    X = X(:)';
    Y = Y(:)';
    d = d(:)';

    th = theta*%pi/180;

    for l=1:length (theta)
        // project each pixel to vector (-sin(th),cos(th))
        Xp = -sin (th(l)) * X + cos (th(l)) * Y;

        ip = Xp + b + 1;

        k = floor (ip);
        frac = ip-k;

        RT(:,l) = nan_accumarray (k',d .* (1-frac),sz) + nan_accumarray (k'+1,d .* frac,sz);
    end
endfunction