pyqt5已有一个self.graphicsView控件，怎问怎样为其加上加载显示图片，并可以在图片上框选红色矩形返回矩形在图片的坐标

你可以使用QGraphicsScene和QGraphicsView来显示图片，并在场景上绘制矩形。下面是一个简单的示例代码：

import sys
from PyQt5.QtWidgets import QApplication, QGraphicsScene, QGraphicsView
from PyQt5.QtGui import QPixmap, QPen, QColor
from PyQt5.QtCore import Qt

class ImageViewer(QGraphicsView):
    def __init__(self):
        super().__init__()
        self.scene = QGraphicsScene(self)
        self.setScene(self.scene)
        self.image_item = None
        self.rect_item = None
        self.start_pos = None
        self.end_pos = None
        self.setDragMode(QGraphicsView.ScrollHandDrag)
        self.setHorizontalScrollBarPolicy(Qt.ScrollBarAlwaysOff)
        self.setVerticalScrollBarPolicy(Qt.ScrollBarAlwaysOff)

    def load_image(self, filename):
        pixmap = QPixmap(filename)
        self.scene.clear()
        self.image_item = self.scene.addPixmap(pixmap)
        self.setSceneRect(pixmap.rect())
        self.fitInView(self.sceneRect(), Qt.KeepAspectRatio)

    def mousePressEvent(self, event):
        if not self.rect_item:
            self.start_pos = event.pos()
            self.rect_item = self.scene.addRect(0, 0, 0, 0, QPen(QColor(255, 0, 0)))
            self.rect_item.setZValue(1)
            self.rect_item.setFlag(self.rect_item.ItemIsMovable, False)
        super().mousePressEvent(event)

    def mouseMoveEvent(self, event):
        if self.rect_item:
            self.end_pos = event.pos()
            rect = self.get_rect_from_points(self.start_pos, self.end_pos)
            self.rect_item.setRect(rect)
        super().mouseMoveEvent(event)

    def mouseReleaseEvent(self, event):
        if self.rect_item:
            self.end_pos = event.pos()
            rect = self.get_rect_from_points(self.start_pos, self.end_pos)
            self.rect_item.setRect(rect)
            self.rect_item = None
            print("Selected Rect:", rect)
        super().mouseReleaseEvent(event)

    def get_rect_from_points(self, pt1, pt2):
        x1, y1 = pt1.x(), pt1.y()
        x2, y2 = pt2.x(), pt2.y()
        return QtCore.QRectF(min(x1, x2), min(y1, y2), abs(x2 - x1), abs(y2 - y1))

if __name__ == '__main__':
    app = QApplication(sys.argv)
    viewer = ImageViewer()
    viewer.load_image("image.jpg")
    viewer.show()
    sys.exit(app.exec_())

这个示例代码实现了以下功能：

1. 加载显示图片
2. 在图片上框选红色矩形
3. 返回矩形在图片的坐标

你可以根据自己的需求进行修改和扩展。