Fedora 41 : OpenCV example with PyQt6.

Today I tested another source code with opencv, numpy, PyQt6 python packages.

I install opencv python package with dnf5 tool:

root@localhost:/home/mythcat# dnf5 install  python3-opencv.x86_64

The source code let you to open, change a image and save using sliders and a reset option.

This is the source code:

import sys
import cv2
import numpy as np
from PyQt6.QtWidgets import QApplication, QMainWindow, QWidget, QVBoxLayout, QLabel, QSlider, QFileDialog, QPushButton, QHBoxLayout
from PyQt6.QtGui import QImage, QPixmap
from PyQt6.QtCore import Qt, pyqtSlot

class MainWindow(QMainWindow):
    def __init__(self):
        super().__init__()
        self.setWindowTitle("Real-Time Color Selection")
        self.setGeometry(100, 100, 1200, 800)

        # Create central widget and main layout
        central_widget = QWidget()
        self.setCentralWidget(central_widget)
        main_layout = QVBoxLayout(central_widget)

        # Create image label
        self.image_label = QLabel()
        main_layout.addWidget(self.image_label)

        # Initialize sliders
        self.lower_h = QSlider(Qt.Orientation.Horizontal)
        self.lower_s = QSlider(Qt.Orientation.Horizontal)
        self.lower_v = QSlider(Qt.Orientation.Horizontal)
        self.upper_h = QSlider(Qt.Orientation.Horizontal)
        self.upper_s = QSlider(Qt.Orientation.Horizontal)
        self.upper_v = QSlider(Qt.Orientation.Horizontal)

        # Set slider ranges
        for slider in [self.lower_h, self.upper_h]:
            slider.setRange(0, 179)
        for slider in [self.lower_s, self.lower_v, self.upper_s, self.upper_v]:
            slider.setRange(0, 255)

        # Set initial slider values
        self.lower_h.setValue(50)
        self.lower_s.setValue(100)
        self.lower_v.setValue(50)
        self.upper_h.setValue(130)
        self.upper_s.setValue(255)
        self.upper_v.setValue(255)

        # Connect sliders to update function
        self.lower_h.valueChanged.connect(self.update_hsv_range)
        self.lower_s.valueChanged.connect(self.update_hsv_range)
        self.lower_v.valueChanged.connect(self.update_hsv_range)
        self.upper_h.valueChanged.connect(self.update_hsv_range)
        self.upper_s.valueChanged.connect(self.update_hsv_range)
        self.upper_v.valueChanged.connect(self.update_hsv_range)

        # Create slider layouts with labels
        sliders_layout = QVBoxLayout()
        
        # Add slider pairs with labels
        slider_pairs = [
            ("Lower Hue", self.lower_h),
            ("Lower Saturation", self.lower_s),
            ("Lower Value", self.lower_v),
            ("Upper Hue", self.upper_h),
            ("Upper Saturation", self.upper_s),
            ("Upper Value", self.upper_v)
        ]

        for label_text, slider in slider_pairs:
            row_layout = QHBoxLayout()
            label = QLabel(label_text)
            label.setMinimumWidth(120)
            row_layout.addWidget(label)
            row_layout.addWidget(slider)
            sliders_layout.addLayout(row_layout)

        main_layout.addLayout(sliders_layout)

        # Add buttons
        button_layout = QHBoxLayout()
        
        self.reset_button = QPushButton("Reset Values")
        self.reset_button.clicked.connect(self.reset_values)
        button_layout.addWidget(self.reset_button)

        self.open_image_button = QPushButton("Open Image")
        self.open_image_button.clicked.connect(self.open_image)
        button_layout.addWidget(self.open_image_button)

        self.save_button = QPushButton("Save Image")
        self.save_button.clicked.connect(self.save_image)
        button_layout.addWidget(self.save_button)
        main_layout.addLayout(button_layout)

        # Process initial image
        self.process_image()

    def process_image(self):
        image_bgr = cv2.imread("image.png")
        if image_bgr is None:
            image_bgr = cv2.imread("default_image.png")
        
        self.image_bgr = image_bgr
        self.image_hsv = cv2.cvtColor(image_bgr, cv2.COLOR_BGR2HSV)

        # Create initial mask using current slider values
        lower_values = np.array([self.lower_h.value(), self.lower_s.value(), self.lower_v.value()])
        upper_values = np.array([self.upper_h.value(), self.upper_s.value(), self.upper_v.value()])
        
        mask_test = cv2.inRange(self.image_hsv, lower_values, upper_values)
        image_bgr_masked = cv2.bitwise_and(image_bgr, image_bgr, mask=mask_test)
        self.image_rgb = cv2.cvtColor(image_bgr_masked, cv2.COLOR_BGR2RGB)
        self.update_image()

    def update_image(self):
        height, width, channel = self.image_rgb.shape
        bytes_per_line = width * channel
        q_image = QImage(self.image_rgb.data, width, height, bytes_per_line, QImage.Format.Format_RGB888)
        pixmap = QPixmap.fromImage(q_image)
        self.image_label.setPixmap(pixmap.scaled(700, 500, Qt.AspectRatioMode.KeepAspectRatio))

    def update_hsv_range(self):
        lower_values = np.array([self.lower_h.value(), self.lower_s.value(), self.lower_v.value()])
        upper_values = np.array([self.upper_h.value(), self.upper_s.value(), self.upper_v.value()])
        mask_test = cv2.inRange(self.image_hsv, lower_values, upper_values)
        image_bgr_masked = cv2.bitwise_and(self.image_bgr, self.image_bgr, mask=mask_test)
        self.image_rgb = cv2.cvtColor(image_bgr_masked, cv2.COLOR_BGR2RGB)
        self.update_image()

    def reset_values(self):
        self.lower_h.setValue(50)
        self.lower_s.setValue(100)
        self.lower_v.setValue(50)
        self.upper_h.setValue(130)
        self.upper_s.setValue(255)
        self.upper_v.setValue(255)

    def open_image(self):
        filename, _ = QFileDialog.getOpenFileName(self, "Select Image File", "", "Image Files (*.png *.jpg *.jpeg)")
        if filename:
            self.image_bgr = cv2.imread(filename)
            if self.image_bgr is not None:
                self.image_hsv = cv2.cvtColor(self.image_bgr, cv2.COLOR_BGR2HSV)
                self.update_hsv_range()  # This will apply current filter and update display

    def save_image(self):
        filename, _ = QFileDialog.getSaveFileName(self, "Save Image", "", "PNG Files (*.png);;JPEG Files (*.jpg)")
        if filename:
            # Make sure filename has an extension
            if not filename.endswith(('.png', '.jpg', '.jpeg')):
                filename += '.png'
            # Convert and save
            output_image = cv2.cvtColor(self.image_rgb, cv2.COLOR_RGB2BGR)
            cv2.imwrite(filename, output_image)

if __name__ == "__main__":
    app = QApplication(sys.argv)
    window = MainWindow()
    window.show()
    sys.exit(app.exec())