PySide在QLabel上按住鼠标左键画方框

 用于截图放大等

import sys
from PySide6.QtWidgets import QApplication, QLabel, QMainWindow
from PySide6.QtGui import QPixmap, QPainter, QPen, QColor
from PySide6.QtCore import Qt, QRect, QPoint


class ImageLabel(QLabel):
    def __init__(self, parent=None):
        super().__init__(parent)
        self.start_pos = QPoint()  # 鼠标起点
        self.end_pos = QPoint()  # 鼠标终点
        self.erase = False  # 擦除
        self.rect = QRect()  # 方框

    # 重新定义鼠标按下事件
    def mousePressEvent(self, event):
        if event.button() == Qt.LeftButton:
            self.start_pos = event.position().toPoint()
            self.erase = False
            self.rect = QRect()

    # 重新定义鼠标移动事件
    def mouseMoveEvent(self, event):
        if self.start_pos:
            self.end_pos = event.position().toPoint()
            self.rect = QRect(self.start_pos, self.end_pos)
            self.update()

    # 重新定义鼠标松开事件
    def mouseReleaseEvent(self, event):
        if event.button() == Qt.LeftButton:
            self.end_pos = event.position().toPoint()
            self.rect = QRect(self.start_pos, self.end_pos)
            self.erase = True    # 这一行决定了松开鼠标后方框是否擦除
            self.update()
            self.normalize_rect()
            # print(self.rect.getRect())

    # 重新定义绘画事件
    def paintEvent(self, event):
        super().paintEvent(event)
        painter = QPainter(self)
        if not self.erase:   # 不擦除
            painter.setPen(QPen(QColor(255, 0, 0, 255), 2, Qt.SolidLine))

        else:    # 擦除
            painter.setPen(QPen(QColor(0, 0, 0, 0), 2, Qt.SolidLine))
        painter.drawRect(self.rect)

    # 将得到的方框所有参数都转换成正数
    def normalize_rect(self):
        x = self.rect.x()
        y = self.rect.y()
        width = self.rect.width()
        height = self.rect.height()

        if width < 0:
            x += width
            width = abs(width)
        if height < 0:
            y += height
            height = abs(height)

        self.rect = QRect(x, y, width, height)
        print(self.rect)


class MainWindow(QMainWindow):
    def __init__(self):
        super().__init__()
        self.image_label = ImageLabel()
        self.setCentralWidget(self.image_label)


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