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## Help please converting Matlab image code

 From: Terry Duell Subject: Help please converting Matlab image code Date: Mon, 25 Apr 2011 10:06:10 +1000 User-agent: Opera Mail/11.10 (Linux)

```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

```