Copy pixels of one image to another. Second image has only one line.

only-one-line-ator.cpp

// This software assumes that all input files have 4 channels (RGB + Alpha)
// and the output.png file only has one line and the total number of pixels in
// both files is equal.

// Use GIMP to create such files.

#include <gdkmm/pixbuf.h>
#include <glibmm/init.h>
#include <gdkmm/wrap_init.h>
#include <cstdlib>

int main(int, char const *[])
{
    Glib::init();
    Gdk::wrap_init();

    Glib::RefPtr<Gdk::Pixbuf> input
        = Gdk::Pixbuf::create_from_file("/home/vinipsmaker/Downloads/input.png");

    Glib::RefPtr<Gdk::Pixbuf> output
        = Gdk::Pixbuf::create_from_file("/home/vinipsmaker/Downloads/output.png");

    guint8 *input_iterator = input->get_pixels();
    guint8 *output_iterator = output->get_pixels();

    const int input_rowpadding
        = input->get_rowstride() - input->get_width() * 4;

    for ( int i = 0 ; i != input->get_height() ; ++i ) {
        for ( int j = 0 ; j != input->get_width() ; ++j ) {
            for ( int k = 0 ; k != 4 ; ++k )
                output_iterator[k] = input_iterator[k];

            input_iterator += 4;
            output_iterator += 4;
        }
        input_iterator += input_rowpadding;
    }

    output->save("/home/vinipsmaker/Downloads/output2.png", "png");

    return EXIT_SUCCESS;
}