unsafe
{
    // Get a pointer to the back buffer.
    // Find the address of the pixel to draw.

    int color_data;
    int pBackBuffer;

    for (i = 0; i < tocopy_bmp.Height; ++i) //tocopy_bmp.height
    {
        for (j = 0; j < tocopy_bmp.Width; ++j) //tocopy_bmp.width
        {
            pBackBuffer = (int)tocopy_bmp.BackBuffer;
            pBackBuffer += i * tocopy_bmp.BackBufferStride;
            pBackBuffer += j * 4;

            color_data = *((int*)pBackBuffer); // this line will increase RAM usage by ~380MB
        }
    }
}