How Matlab coder converts image to unsigned char

Hi,

I am working on the code converted by Matlab coder, the coder converts the image to a single array of unsigned Char[....] according to the image size. I would like to use this converted unsigned array and split it into img[c][y][x] using python for another application. For this purpose. I would like to know how the Matlab coder combines the images. It would be great if someone could explain me regarding this.

Thanks and regards, Venkatesh

Answer 1

[Ryan Livingston]

The generated code stores the array in column-major order just like MATLAB:

http://www.mathworks.com/help/matlab/matlab_external/matlab-data.html#f22019

http://en.wikipedia.org/wiki/Row-major_order#Column-major_order

So, as you iterate over the char[...] array you will access the elements of the first column in order, then the second column and so on until you reach the last column in the sub array A(:,:,1). Then you will continue on to iterate over the columns of A(:,:,2) in the same fashion and finally over A(:,:,3).

You can see the order by executing the loop:

for k = 1:numel(A)
    disp(A(k));
end

in MATLAB where A is your 3 dimensional array. This goes through the elements of A in the same order that they are stored in the generated code.

If you are using NumPy, note that the array types can be configured to be stored in row-major or column-major order by passing the order argument. You should be able to use order='F' to tell it to consider the array stored in Fortran or column-major order. For example:

http://docs.scipy.org/doc/numpy/reference/generated/numpy.zeros.html#numpy.zeros