Passing a 2D array of unknown size into a function in C++

Question

I'm trying to input a 2D array into a function. I don't know the number of rows or columns to this array and it was loaded into c++ via CImg. This is what I have:

// Main function:
int main()
{
    int rows, columns;
    float summation;
    CImg<unsigned char> prettypicture("prettypicture.pgm");
    rows = prettypicture.height();
    columns = prettypicture.width();

    summation = SUM(prettypicture[][], rows, columns);
}

// Summation function:
float SUM(int **picture, int rows, int column)
{
... // there is some code here but I don think this is important.
}

I would like to pass the array into the summation function and I'm aware that I should be using pointers in some way, but I'm not sure how to do this. Any help would be much appreciated.

Thank you

(sorry for being a noob)

Topological Sort · Accepted Answer · 2016-02-22 17:55:52Z

1

Try this:

summation = SUM(prettypicture.data(), rows, columns);

and make your SUM function look like this:

float SUM(char* picture, int rows, int column) ...

You need to pass in data (if you want a pointer to the data) because that's what CImg provides. It's a pointer to character because that's the kind of CImg you have; and it's a char*, not char**, because that's what data provides.

You didn't show us the inside of the SUM function, so I wonder if you might do well to pass in the CImg instead of just its data, and call the member function atXY that takes a position. Hard to say without seeing more.

For more information on data and other member functions of CImg, see http://cimg.eu/reference/structcimg__library_1_1CImg.html .

edited Feb 22, 2016 at 17:55

answered Feb 22, 2016 at 17:48

Topological Sort

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1 Comment

ProNoobSry Over a year ago

Thank you very much, just what I needed :D

Hamdor · Accepted Answer · 2016-02-22 17:46:13Z

0

why not pass it as reference?

summation = SUM(prettypicture);

float SUM(const CImg<unsinged char>& picture) {
  // ...
}

answered Feb 22, 2016 at 17:46

Hamdor

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