self.setDragMode(QGraphicsView.ScrollHandDrag)

This line of code sets the drag mode of a QGraphicsView object to "ScrollHandDrag". This means that the user can drag the view around by clicking and dragging with the mouse button, as if they were scrolling the view by hand. This is a common feature in image viewing or map applications.

相关问题

将文件夹的图片生成到QtWidgets.QGraphicsView(self.centralwidget)

好的，我理解你的问题了。你想将一个文件夹中的所有图片显示在Qt的QGraphicsView中。我可以给你提供一些参考。

首先，你需要安装Pillow模块，这是Python的图像处理库。你可以使用pip命令来安装它：

pip install Pillow

然后，你需要编写代码来读取文件夹中的所有图片，创建QPixmap对象并将其添加到QGraphicsScene中。下面是一个简单的Python函数，它会读取一个文件夹中的所有图片，并将它们显示在QGraphicsView中：

from PyQt5.QtWidgets import QGraphicsScene, QGraphicsPixmapItem
from PyQt5.QtGui import QPixmap
import os

def load_images(folder_path, scene):
    # 遍历文件夹中的所有文件
    for filename in os.listdir(folder_path):
        # 如果是图片文件
        if filename.endswith(".jpg") or filename.endswith(".png"):
            # 创建QPixmap对象
            pixmap = QPixmap(os.path.join(folder_path, filename))
            # 创建QGraphicsPixmapItem对象
            pixmap_item = QGraphicsPixmapItem(pixmap)
            # 将QGraphicsPixmapItem对象添加到QGraphicsScene中
            scene.addItem(pixmap_item)

在你的Qt应用程序中，你可以这样使用它：

from PyQt5.QtWidgets import QMainWindow, QGraphicsView, QGraphicsScene
from PyQt5.QtCore import Qt
import sys

class MainWindow(QMainWindow):

    def __init__(self):
        super().__init__()

        # 创建QGraphicsView和QGraphicsScene
        self.view = QGraphicsView(self.centralwidget)
        self.scene = QGraphicsScene(self.view)
        self.view.setScene(self.scene)

        # 加载图片
        load_images("path/to/folder", self.scene)

        # 设置QGraphicsView的属性
        self.view.setRenderHint(QPainter.Antialiasing)
        self.view.setDragMode(QGraphicsView.ScrollHandDrag)
        self.view.setViewportUpdateMode(QGraphicsView.FullViewportUpdate)
        self.view.setAlignment(Qt.AlignLeft | Qt.AlignTop)

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

注意，这只是一个简单的示例，你可以根据你的需要进行修改和扩展。

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。