Load set of images - Matlab-->C++ translation

I have a Matlab script that I'm trying to convert to C++ (see below) because it is extremely slow. I'm a C++ newbie and to start I tried using codegen but it doesn't work (I got the message ??? This text contains non-empty top-level expressions. It appears to be a script.)

Do you have any suggestion on how to start to convert the code? Also, what is the best C++ function to do the job of fitsread?

Here is my code:

clear;

number_projections = 10;
imgs_per_proj = 2000; % Number of images per projection

% Lets load the reference images relative to the various wavelengths

R1 = zeros(imgs_per_proj, 512, 512);
R2 = zeros(imgs_per_proj, 512, 512);

l = 0;
for k = 1:imgs_per_proj
    s = sprintf('Ref/R1_000_%05i.fits',k-1);
    t = sprintf('Ref/R2_000_%05i.fits',k-1);
    l = l + 1;
    R1(l,:,:) = fitsread(s);
    R2(l,:,:) = fitsread(t);
end

Solution

codegen requires that the MATLAB code you're trying to convert be in a function and it seems you are trying to convert a script

However, even if you do that, fitsread does not appear to be a supported function within codegen. Here's a list of supported functions: http://www.mathworks.com/help/simulink/ug/functions-supported-for-code-generation--alphabetical-list.html

There's no "built-in" function within C++ that's going to replace fitsread - for that you need a library. There's a C++ FITS library called CCFits that you can find here: http://heasarc.gsfc.nasa.gov/fitsio/CCfits/

They should have tutorials that you could follow.