Help please converting Matlab image code

[Terry Duell]

Hullo All,
I have run in to difficulty finding a suitable 'translation' of some  
Matlab code.
As I understand it, the purpose of this code is to adjust the histogram of  
of 'gray_in' to match reference image 'gray_reference'.

The code obtains a histogram of reference gray image ('grey_reference'  
uint8 0-255)

 hist_reference = hist(double(gray_reference(:)),[0:255]);

 The output, 'hist_reference' appears to be a 255 vector of the bin counts.

This is then used in the 'histeq' function along with another gray image  
('gray_in' double 0-1);

 [j,t] = histeq(gray_in,hist_reference);

and the output, 't' is then massaged to produce the an output image  
('out') which is one of the 3 images making up an RGB.


%% Now compute output image
  for a=1:size(gray_in,3)
  q = in(:,:,a);
  qm=interp1([0:255]/256,t(:),q(:));
  out(:,:,a) = uint8(256 * reshape(qm,size(gray_in(:,:,a))));

The problem I have is that the Octave 'histeq' function baulks at being  
passed the vector 'hist_reference', as 'histeq' calls 'gray2ind' which  
will only accept a positive integer as it's second argument.

I have spent some time looking through the available Octave functions, but  
have not yet seen any way of reproducing the effect of this code.

Does anyone have any suggestions as to how this might be done?


Cheers,
--
Regards,
Terry Duell