Add a printing function that displays png_image

rust/coffi/src/main.rs

@@ -28,11 +28,23 @@ fn main() {
    let x = unsafe { cos(3.1415) };
    println!("cos(3.1415) = {}", x);
    let mut img: png_image;
    fn get_message(msg: [u8; 64]) -> String {
        let mut vec = Vec::new();
        for i in 0..64 {
            vec.push(msg[i]);
        }
        String::from_utf8(vec).unwrap()
    }
    fn print_img(img: &png_image) {
        println!("{}x{} {} {} {} {} {} {}", img.width, img.height, img.version, img.format, img.flags, img.colormap_entries, img.warning_or_error, get_message(img.message))
    }
    unsafe {
        img = std::mem::zeroed();
        let mut img: png_image = std::mem::zeroed();
        print_img(&img);
        let res = png_image_begin_read_from_file(&mut img, "mei.png".as_ptr());
        println!("read_from_file: {}", res);
        println!("{}x{}", img.width, img.height);
        print_img(&img);
    }
}