pyqt5 graphicsView 加载显示图片，有如下功能：1、滑动滚轮可以根据鼠标位置进行放大缩小，可以在图片上用鼠标框选矩形，并返回矩形在图片上的实际坐标

可以使用以下代码实现：

import sys
from PyQt5.QtCore import Qt, QRectF
from PyQt5.QtGui import QPixmap, QColor, QPainter
from PyQt5.QtWidgets import QGraphicsScene, QGraphicsView, QGraphicsRectItem, QApplication


class ImageViewer(QGraphicsView):
    def __init__(self, pixmap):
        super().__init__()
        self.scene = QGraphicsScene(self)
        self.setScene(self.scene)
        self.setAlignment(Qt.AlignLeft | Qt.AlignTop)
        self.setHorizontalScrollBarPolicy(Qt.ScrollBarAlwaysOff)
        self.setVerticalScrollBarPolicy(Qt.ScrollBarAlwaysOff)
        self.setRenderHint(QPainter.Antialiasing)
        self.setDragMode(QGraphicsView.ScrollHandDrag)
        self.setFixedSize(pixmap.width(), pixmap.height())
        self.rect_item = None
        self.scene.addPixmap(pixmap)

    def wheelEvent(self, event):
        delta = event.angleDelta().y()
        factor = 1.1 if delta > 0 else 0.9
        zoom_point = self.mapToScene(event.pos())
        self.scale(factor, factor)
        self.centerOn(zoom_point)

    def mousePressEvent(self, event):
        if event.button() == Qt.LeftButton:
            pos = event.pos()
            scene_pos = self.mapToScene(pos)
            self.rect_item = QGraphicsRectItem(QRectF(scene_pos, scene_pos))
            self.rect_item.setPen(QColor(255, 0, 0))
            self.scene.addItem(self.rect_item)

    def mouseMoveEvent(self, event):
        if self.rect_item is not None:
            pos = event.pos()
            scene_pos = self.mapToScene(pos)
            rect = QRectF(self.rect_item.rect().topLeft(), scene_pos).normalized()
            self.rect_item.setRect(rect)

    def mouseReleaseEvent(self, event):
        if event.button() == Qt.LeftButton:
            if self.rect_item is not None:
                rect = self.rect_item.rect()
                image_rect = QRectF(0, 0, self.scene.width(), self.scene.height())
                if rect.intersects(image_rect):
                    rect = rect.intersected(image_rect)
                transform = self.transform().inverted()[0]
                rect = transform.mapRect(rect)
                x, y, w, h = rect.getCoords()
                print(f"Selected Rect: ({x}, {y}, {w}, {h})")
                self.scene.removeItem(self.rect_item)
                self.rect_item = None


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

这段代码实现了以下功能：

1. 加载并显示图片。
2. 使用滚轮可以放大缩小图片，并以鼠标位置为中心。
3. 使用鼠标在图片上框选矩形，并返回矩形在图片上的实际坐标。