pyqt5如何画任意形状的矩形，可拖动改变大小，可旋转

可以使用QGraphicsItem实现。具体操作流程可以参考以下代码：

from PyQt5.QtCore import QPointF, QRectF, Qt
from PyQt5.QtGui import QBrush, QColor, QPainter, QPen
from PyQt5.QtWidgets import QApplication, QGraphicsItem, QGraphicsScene, QGraphicsView


class RectItem(QGraphicsItem):
    def __init__(self, rect, parent=None):
        super().__init__(parent)
        self.rect = rect
        self.setFlags(QGraphicsItem.ItemIsMovable |
                      QGraphicsItem.ItemIsSelectable |
                      QGraphicsItem.ItemSendsGeometryChanges)
        self.setAcceptHoverEvents(True)
        self.setCursor(Qt.SizeAllCursor)

    def boundingRect(self):
        return self.rect.normalized()

    def paint(self, painter, option, widget):
        pen = QPen(QColor(0, 0, 255), 2, Qt.SolidLine)
        brush = QBrush(QColor(255, 255, 255, 128), Qt.SolidPattern)
        painter.setPen(pen)
        painter.setBrush(brush)
        painter.drawRect(self.rect)

    def hoverMoveEvent(self, event):
        rect = self.rect.adjusted(7, 7, -7, -7)
        if rect.contains(event.pos()):
            self.setCursor(Qt.SizeAllCursor)
        else:
            self.setCursor(Qt.ArrowCursor)

    def mousePressEvent(self, event):
        self.mouse_pos = event.pos()

    def mouseMoveEvent(self, event):
        if event.buttons() == Qt.LeftButton:
            dx = event.pos().x() - self.mouse_pos.x()
            dy = event.pos().y() - self.mouse_pos.y()
            self.mouse_pos = event.pos()
            self.rect.translate(dx, dy)
            self.update()

    def itemChange(self, change, value):
        if change == QGraphicsItem.ItemPositionChange:
            self.scene().update()
        return super().itemChange(change, value)


class GraphicsScene(QGraphicsScene):
    def __init__(self, rect):
        super().__init__()
        self.rect_item = RectItem(rect)
        self.addItem(self.rect_item)


if __name__ == '__main__':
    rect = QRectF(50, 50, 100, 80)
    app = QApplication([])
    view = QGraphicsView()
    view.setRenderHints(QPainter.Antialiasing |
                        QPainter.SmoothPixmapTransform)
    scene = GraphicsScene(rect)
    scene.setSceneRect(0, 0, 300, 200)
    view.setScene(scene)
    view.show()
    app.exec_()

该代码演示了如何使用QGraphicsItem绘制可移动、可缩放、可旋转的矩形。