VideoCapture.py

import cv2 as cv

class VideoCapture(cv.VideoCapture):
    '''Subclass class of cv2.VideoCapture implemented
    to simplify the interface for this Applications
    VideoCapturing requirements
    '''
    _1080p = (1920, 1080)
    _720p = (1280, 720)
    _480p = (480, 640)

    def __init__(self, res=_480p):
        super().__init__(0)
        self.set_resolution(res)

    def set_frame_rate(self, fps):
        '''Sets the framerate of capture object

        @todo investigate if this has any affect on PiCam
        streaming.

        Params:
            fps (float) : framerate in frames per second
        '''
        self.set(cv.CAP_PROP_FPS, fps)
    
    def set_resolution(self, resolution):
        '''Sets the frameresolution rate of capture object

        Params:
            resolution (tuple(int)) : WxH resolution
        '''
        w, h = resolution
        self.set(cv.CAP_PROP_FRAME_WIDTH, w)
        self.set(cv.CAP_PROP_FRAME_HEIGHT, h)
    
    def capture(self, fps=None):
        '''Captures next frame, and returns a .JPG encoded 
        image
        
        Params:
            fps (int) : frame_rate to display

        Returns jpg (obj) : encoded jpg object
        '''

        _, frame = self.read()
        self._set_frame_text(frame, fps)
        _, jpg = cv.imencode('.jpg', frame)

        return jpg
    
    def _set_frame_text(self, frame, text):
        '''Sets the text of a frame object
        Params:
            frame (obj) : opencv frame
            text (mixed) : text to display over the frame
        '''
        cv.putText(
            img=frame, text=f"{text}", org=(10,50),
            fontFace=1, fontScale=1, color=(0,0,255), thickness=2
        )