```rust
use std::fs::File;
use std::io::Read;
use base64::{Engine as _, engine::general_purpose};
fn main() {
let mut file = File::open("x.png").unwrap();
let mut buffer = vec![];
file.read_to_end(&mut buffer).unwrap();
let base64_str = general_purpose::STANDARD_NO_PAD.encode(buffer);
println!("{}",base64_str);
}
```