How to Show Text on GUI on Video

Question

My code below generates detected text on video pressing snapshot button. I would like to learn how to print the generated text on live video. I could do that without GUI but connecting functions to GUI is my problem. What I want to adapt is:

painter.drawText(0, 20, "text"); 

it worked but only for static text. My text changes with button press and I want to do it with button press with the change of text.

import sys
from os import path

import cv2
import numpy as np

from PyQt5 import QtCore
from PyQt5 import QtWidgets
from PyQt5 import QtGui

import pytesseract
from PIL import Image
from pytesseract import image_to_string
from gtts import gTTS
import os


pytesseract.pytesseract.tesseract_cmd = r"C:\Program Files\Tesseract-OCR\tesseract.exe"


tessdata_dir_config = r'--tessdata-dir "C:\Program Files\Tesseract-OCR\tessdata"'



class RecordVideo(QtCore.QObject):
    image_data = QtCore.pyqtSignal(np.ndarray)

    def __init__(self, parent=None):
        super().__init__(parent)
        self.camera = cv2.VideoCapture(0)

        self.timer = QtCore.QBasicTimer()

    def start_recording(self):
        self.timer.start(0, self)

    
    def timerEvent(self, event):
        if (event.timerId() != self.timer.timerId()):
            return

        read, data = self.camera.read()
        if read:
            self.image_data.emit(data)
    def framesave(self):
        
        read, data = self.camera.read()
        if read:
            cv2.imwrite('a.png',data)
            img=Image.fromarray(data)
            img.load()
            
            text=pytesseract.image_to_string(img, lang='spa', config=tessdata_dir_config)
        


class FaceDetectionWidget(QtWidgets.QWidget):
    def __init__(self, parent=None):
        super().__init__(parent)
        self.image = QtGui.QImage()
        self._red = (0, 0, 255)
        self._width = 2
        self._min_size = (30, 30)


    def image_data_slot(self, image_data):


        
        self.image = self.get_qimage(image_data)
        if self.image.size() != self.size():
            self.setFixedSize(self.image.size())

        self.update()
    
        
        
    def get_qimage(self, image: np.ndarray):
        height, width, colors = image.shape
        bytesPerLine = 3 * width
        QImage = QtGui.QImage

        image = QImage(image.data,
                       width,
                       height,
                       bytesPerLine,
                       QImage.Format_RGB888)

        image = image.rgbSwapped()
        return image

    def paintEvent(self, event):
        painter = QtGui.QPainter(self)
        painter.drawImage(0, 0, self.image)
        self.image = QtGui.QImage()


class MainWidget(QtWidgets.QWidget):
    def __init__(self, parent=None):
        super().__init__(parent)
        
        self.face_detection_widget = FaceDetectionWidget()

        # TODO: set video port
        self.record_video = RecordVideo()

        image_data_slot = self.face_detection_widget.image_data_slot
        self.record_video.image_data.connect(image_data_slot)

        layout = QtWidgets.QVBoxLayout()

        layout.addWidget(self.face_detection_widget)
        self.run_button = QtWidgets.QPushButton('Start')
        layout.addWidget(self.run_button)

        self.run_button.clicked.connect(self.record_video.start_recording)

        self.screenshot = QtWidgets.QPushButton('Snap Shot')
        layout.addWidget(self.screenshot)

        self.screenshot.clicked.connect(self.record_video.framesave)
        self.setLayout(layout)


    
def main():
    app = QtWidgets.QApplication(sys.argv)

    main_window = QtWidgets.QMainWindow()
    main_widget = MainWidget()
    main_window.setCentralWidget(main_widget)
    main_window.show()

    sys.exit(app.exec_())


if __name__ == '__main__':

    main()

Answer 1

Create an instance variable (or a property) with the text that you want to draw, then when the text changes call update().

class FaceDetectionWidget(QtWidgets.QWidget):
    _text = ''

    # ...

    @property
    def text(self):
        return self._text

    @text.setter
    def text(self, text):
        if text == self._text:
            return
        self._text = text
        self.update()

    # ...

    def paintEvent(self, event):
        painter = QtGui.QPainter(self)
        painter.drawImage(0, 0, self.image)
        self.image = QtGui.QImage()
        if self._text:
            painter.drawText(0, 20, self._text)


class MainWidget(QtWidgets.QWidget):
    def __init__(self, parent=None):
        super().__init__(parent)
        # ...
        self.testButton = QtWidgets.QPushButton('write text')
        layout.addWidget(self.testButton)
        self.testButton.clicked.connect(self.addText)

    def addText(self):
        self.face_detection_widget.text = 'some random text'