[SOLVED] random gaussians on an image - matlab

[keremcant]

Hi, I am trying to create some Gaussian distributions and put them on an image. The Gaussians have randomly created parameter (amplitude, position and standard deviation). First I put the parameters into vectors or matrices, then I am using ngrid() function to get a 2d space to create the Gaussians, however i get an error (since possibly mathematical operations with ngrid values is not trivial...). The error is:

  ??? Error using ==> minus
Integers can only be combined
with integers of the same class,
or scalar doubles.
Error in ==> ss_gauss_fit at 23
  gauss = amp(i)*
  exp(-((x-xc).^2 +
  (y-yc).^2)./(2*std(i)));

and the code is here:

clear all;
image = uint8(zeros([300 300]));
imsize=size(image);

noOfGauss=10;
maxAmpGauss=160;
stdMax=15;
stdMin=3;

for i=1:noOfGauss
    posn(:,:,i)=[  uint8(imsize(1)*rand())   uint8(imsize(2)*rand())  ];
    std(i)=stdMin+uint8((stdMax-stdMin)*rand());
    amp(i)= uint8(rand()* maxAmpGauss);
end

% draw the gaussians on blank image
for i=1:noOfGauss
    [x,y] = ndgrid(1:imsize(1), 1:imsize(2));
    xc = posn(1,1,i);
    yc = posn(1,2,i);
    gauss = amp(i)* exp(-((x-xc).^2 + (y-yc).^2)./(2*std(i)));

    image = image + gauss;
end

What can i do to fix this situation?
Thanks in advance

 

[emresel]

Hi keremcant;
I can't understand your code exactly but if your aim is adding some gaussian noise on an image. Then you can use imnoise function.
Or another solution is first generate a gaussian mxn vector using randn, and use "reshape" function to make noise vector look like image matrix, then simply add to image.

Hope helps

 

[keremcant]

Hi emresel,
I am actually not trying to add gaussian profiled noise. These gaussians I am trying to add are my signals, like point-spread-functions I get while imaging point shaped objects.

Actually I fixed the problem with some help from somewhere else. My problem occurred while trying to use together i)an 2d matrix created by ngrid as a mesh to create the gaussians with and ii) changing the parameters of the gaussians i want to create in a for loop.

I changed it in the following way:
Instead of this line

gauss = amp(i)* exp(-((x-xc).^2 + (y-yc).^2)./(2*std(i)));

I am using this line:

gg = amp(i)*fspecial('gaussian', gaussSize, double(std(i)));

Of course I define a gauss size etc, but i can utilize this function in a for loop, which was mainly my problem.
Thanks for your help.