In today’s lesson, we add a clean, real-time Frames Per Second (FPS) counter directly onto our live OpenCV video window. Displaying FPS on screen is an essential tool for anyone working with camera-based AI projects on the Raspberry Pi. It gives you immediate feedback on your actual processing performance, helps with optimization, and makes your projects look more professional and polished.
In this lesson, we configure the Picamera2 library to run at 1280×720 resolution with a target of 60 frames per second. We then implement a smoothed FPS calculation using a weighted rolling average, which prevents the displayed value from jumping around wildly. Finally, we overlay the FPS text in the lower-left corner of the video frame using OpenCV’s putText() function, with font size and thickness that scale appropriately with the resolution.
This technique forms an important foundation for future lessons, as we will continue adding more information and graphics directly onto the live video stream. Understanding how to efficiently display performance metrics is key to developing responsive and practical edge AI applications.
In this lesson, this is the code which we develop:
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import cv2 import time from picamera2 import Picamera2 piCam = Picamera2() W=1280 H=720 tStart = time.time() fps = 0 RES = (W,H) piCam.preview_configuration.main.size = RES piCam.preview_configuration.main.format = "RGB888" piCam.preview_configuration.controls.FrameRate=60 piCam.preview_configuration.align() piCam.configure("preview") piCam.start() textLowerLeft = (int(W*.01),int(H*.05)) fontFace = cv2.FONT_HERSHEY_SIMPLEX fontThickness = int(W/425) fontScale = H*.0015 fontColor = (0,0,255) while True: deltaT = time.time() - tStart tStart=time.time() fps = fps*.95 + (1/deltaT)*.05 frame= piCam.capture_array() frame=cv2.flip(frame,-1) myText = "FPS: "+str(round(fps,1)) cv2.putText(frame,myText,textLowerLeft,fontFace,fontScale,fontColor,fontThickness) cv2.imshow("Camera", frame) cv2.moveWindow("Camera",0,60) if cv2.waitKey(1)==ord('q'): break cv2.destroyAllWindows() print('Program Terminated') |