pyqt5 graphicsView 加载显示图片，在图片上鼠标框选红色矩形并返回矩形在图片上的实际坐标

要获取在图片上的实际坐标，需要知道图片的缩放比例。可以使用QGraphicsPixmapItem来替代QGraphicsScene.addPixmap()方法，这样可以获取到图片的缩放比例。然后将鼠标事件中的坐标转换为实际坐标。

下面是修改后的代码：

from PyQt5.QtCore import Qt, QRectF
from PyQt5.QtGui import QPixmap, QColor, QPen
from PyQt5.QtWidgets import QGraphicsScene, QGraphicsView, QGraphicsPixmapItem, QApplication, QMainWindow

class GraphicsView(QGraphicsView):
    def __init__(self, parent=None):
        super(GraphicsView, self).__init__(parent)
        self.scene = QGraphicsScene(self)
        self.setScene(self.scene)
        self.setDragMode(QGraphicsView.ScrollHandDrag)
        self.setRenderHint(QPainter.Antialiasing)

    def setImage(self, image):
        self.image = QPixmap(image)
        self.scene.clear()
        self.scene.setSceneRect(QRectF(self.image.rect()))
        self.pixmap_item = QGraphicsPixmapItem(self.image)
        self.scene.addItem(self.pixmap_item)

    def mousePressEvent(self, event):
        if event.button() == Qt.LeftButton:
            self.origin = event.pos()
            self.rubberBand = QGraphicsRectItem()
            self.rubberBand.setPen(QPen(QColor(Qt.red), 2, Qt.SolidLine))
            self.scene.addItem(self.rubberBand)
            self.rubberBand.setPos(self.mapToScene(self.origin))

    def mouseMoveEvent(self, event):
        if hasattr(self, 'rubberBand'):
            self.rubberBand.setRect(QRectF(self.origin, event.pos()).normalized())

    def mouseReleaseEvent(self, event):
        if hasattr(self, 'rubberBand'):
            rect = self.rubberBand.rect()
            rect = rect.normalized()
            rect = QRectF(self.mapToScene(rect.topLeft()), self.mapToScene(rect.bottomRight()))
            x, y = rect.x() / self.pixmap_item.pixmap().width(), rect.y() / self.pixmap_item.pixmap().height()
            w, h = rect.width() / self.pixmap_item.pixmap().width(), rect.height() / self.pixmap_item.pixmap().height()
            print(x, y, w, h)
            self.scene.removeItem(self.rubberBand)
            del self.rubberBand

class MainWindow(QMainWindow):
    def __init__(self, parent=None):
        super(MainWindow, self).__init__(parent)
        self.view = GraphicsView(self)
        self.setCentralWidget(self.view)
        self.view.setImage('image.jpg')
        self.show()

if __name__ == '__main__':
    import sys

    app = QApplication(sys.argv)
    window = MainWindow()
    sys.exit(app.exec_())

在上面的代码中，我们使用QGraphicsPixmapItem来添加图片，并在释放鼠标时将矩形的坐标转换为实际坐标。`x, y, w, h`分别表示矩形左上角的横坐标和纵坐标以及矩形的宽度和高度，都是相对于图片实际的宽度和高度的比例。