add example: stream video capture over http

examples/video_capture_http_stream.rs

@@ -0,0 +1,48 @@
+/// Example code to stream mjpeg over http
+use std::io::Write;
+use std::net::{SocketAddr, TcpListener};
+
+// VideoCaptureTrait doesn't get used when binding to opencv 3.4
+#[allow(unused_imports)]
+use opencv::videoio::VideoCaptureTrait;
+
+use opencv::core::{Mat, Vector};
+use opencv::imgcodecs::{imencode, IMWRITE_JPEG_QUALITY};
+use opencv::videoio::{VideoCapture, VideoCaptureTraitConst, CAP_ANY};
+
+const BASE_RESPONSE: &[u8] = b"HTTP/1.1 200 OK\r\nContent-Type: multipart/x-mixed-replace; boundary=frame\r\n\r\n";
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+	let mut cam = VideoCapture::new(0, CAP_ANY)?;
+	assert!(cam.is_opened()?, "Unable to open default camera!");
+
+	// Bind listener to a port
+	let address: SocketAddr = "127.0.0.1:8080".parse()?;
+	let listener = TcpListener::bind(address)?;
+	println!("Listening for connections at {}", address.to_string());
+
+	// Accept the first incoming connection
+	let (mut stream, addr) = listener.accept()?;
+	println!("Client connected: {}", addr);
+
+	// Write intial response
+	stream.write_all(BASE_RESPONSE)?;
+
+	// Reduce jpeg quality for streaming
+	let encode_params = Vector::from_slice(&[IMWRITE_JPEG_QUALITY, 70]);
+	let mut buffer = Mat::default();
+	let mut frame = Vector::default();
+	loop {
+		// Read frame from the camera & encode it
+		cam.read(&mut buffer)?;
+		imencode(".jpg", &buffer, &mut frame, &encode_params)?;
+
+		// Construct HTTP frame and send it to the peer
+		let header = format!(
+			"--frame\r\nContent-Type: image/jpeg\r\nContent-Length: {}\r\n\r\n",
+			frame.len()
+		);
+		let packet = [header.as_bytes(), frame.as_slice()].concat();
+		stream.write_all(&packet)?;
+	}
+}