adding cam viewer

rpi-cam-viewer.py

@@ -0,0 +1,40 @@
+import io
+from flask import Flask, Response
+from picamera2 import Picamera2
+from PIL import Image
+
+WIDTH, HEIGHT = 640, 400
+
+cam = Picamera2()
+cam.configure(cam.create_video_configuration(
+    main={"size": (WIDTH, HEIGHT), "format": "YUV420"},
+    controls={"FrameRate": 30}))
+cam.start()
+
+app = Flask(__name__)
+
+
+def frames():
+    while True:
+        gray = cam.capture_array("main")[:HEIGHT, :WIDTH]   # Y plane = greyscale image
+        buf = io.BytesIO()
+        Image.fromarray(gray).save(buf, format="JPEG", quality=70)
+        yield b"--frame\r\nContent-Type: image/jpeg\r\n\r\n" + buf.getvalue() + b"\r\n"
+
+
+@app.route("/")
+def index():
+    return ('<html><body style="margin:0;background:#111">'
+            '<img src="/stream" style="width:100%"></body></html>')
+
+
+@app.route("/stream")
+def stream():
+    return Response(frames(), mimetype="multipart/x-mixed-replace; boundary=frame")
+
+
+if __name__ == "__main__":
+    try:
+        app.run(host="0.0.0.0", port=8000, threaded=True)
+    finally:
+        cam.stop()