python - 用鼠标调整 QGraphicsItem 的大小

Question

放置一个rectangle之后在 QGraphicsScene 中并使其可以用鼠标移动，如何用鼠标调整它的大小？

如果没有人知道答案，举个例子也不错，我正在使用 PyQt4 在 Python 中进行开发。

我知道这里有类似的问题，但他们没有分别回答我。

我的简化代码:

import sys
from PyQt4.QtCore import *
from PyQt4.QtGui import *

app = QApplication(sys.argv)

grview = QGraphicsView()
scene = QGraphicsScene()
scene.setSceneRect(0, 0, 512, 512)

scene.addPixmap(QPixmap('01.png'))
grview.setScene(scene)

item = QGraphicsRectItem(0, 0, 300, 150)

pen = QPen(Qt.darkMagenta)
pen.setWidth(4)
item.setPen(pen)

item.setFlag(QGraphicsItem.ItemIsMovable)
scene.addItem(item)

grview.fitInView(scene.sceneRect(), Qt.KeepAspectRatio)

grview.show()

sys.exit(app.exec_())

Answer 1

您需要自己实现调整大小。为此，您需要继承 QGraphicsRectItem 并实现鼠标事件处理程序:mousePressEvent、mouseMoveEvent、mouseReleaseEvent。 总体思路如下:

• 您创建一组可用于调整形状大小的 handle 。
• 通过跟踪 handle 位置变化，您可以计算形状的新几何形状。

我之前写了一些代码，它可以完美地与 PyQt5 一起工作，但它也应该与 PyQt4 一起工作。您应该能够根据需要调整它:

import sys

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


class GraphicsRectItem(QGraphicsRectItem):

    handleTopLeft = 1
    handleTopMiddle = 2
    handleTopRight = 3
    handleMiddleLeft = 4
    handleMiddleRight = 5
    handleBottomLeft = 6
    handleBottomMiddle = 7
    handleBottomRight = 8

    handleSize = +8.0
    handleSpace = -4.0

    handleCursors = {
        handleTopLeft: Qt.SizeFDiagCursor,
        handleTopMiddle: Qt.SizeVerCursor,
        handleTopRight: Qt.SizeBDiagCursor,
        handleMiddleLeft: Qt.SizeHorCursor,
        handleMiddleRight: Qt.SizeHorCursor,
        handleBottomLeft: Qt.SizeBDiagCursor,
        handleBottomMiddle: Qt.SizeVerCursor,
        handleBottomRight: Qt.SizeFDiagCursor,
    }

    def __init__(self, *args):
        """
        Initialize the shape.
        """
        super().__init__(*args)
        self.handles = {}
        self.handleSelected = None
        self.mousePressPos = None
        self.mousePressRect = None
        self.setAcceptHoverEvents(True)
        self.setFlag(QGraphicsItem.ItemIsMovable, True)
        self.setFlag(QGraphicsItem.ItemIsSelectable, True)
        self.setFlag(QGraphicsItem.ItemSendsGeometryChanges, True)
        self.setFlag(QGraphicsItem.ItemIsFocusable, True)
        self.updateHandlesPos()

    def handleAt(self, point):
        """
        Returns the resize handle below the given point.
        """
        for k, v, in self.handles.items():
            if v.contains(point):
                return k
        return None

    def hoverMoveEvent(self, moveEvent):
        """
        Executed when the mouse moves over the shape (NOT PRESSED).
        """
        if self.isSelected():
            handle = self.handleAt(moveEvent.pos())
            cursor = Qt.ArrowCursor if handle is None else self.handleCursors[handle]
            self.setCursor(cursor)
        super().hoverMoveEvent(moveEvent)

    def hoverLeaveEvent(self, moveEvent):
        """
        Executed when the mouse leaves the shape (NOT PRESSED).
        """
        self.setCursor(Qt.ArrowCursor)
        super().hoverLeaveEvent(moveEvent)

    def mousePressEvent(self, mouseEvent):
        """
        Executed when the mouse is pressed on the item.
        """
        self.handleSelected = self.handleAt(mouseEvent.pos())
        if self.handleSelected:
            self.mousePressPos = mouseEvent.pos()
            self.mousePressRect = self.boundingRect()
        super().mousePressEvent(mouseEvent)

    def mouseMoveEvent(self, mouseEvent):
        """
        Executed when the mouse is being moved over the item while being pressed.
        """
        if self.handleSelected is not None:
            self.interactiveResize(mouseEvent.pos())
        else:
            super().mouseMoveEvent(mouseEvent)

    def mouseReleaseEvent(self, mouseEvent):
        """
        Executed when the mouse is released from the item.
        """
        super().mouseReleaseEvent(mouseEvent)
        self.handleSelected = None
        self.mousePressPos = None
        self.mousePressRect = None
        self.update()

    def boundingRect(self):
        """
        Returns the bounding rect of the shape (including the resize handles).
        """
        o = self.handleSize + self.handleSpace
        return self.rect().adjusted(-o, -o, o, o)

    def updateHandlesPos(self):
        """
        Update current resize handles according to the shape size and position.
        """
        s = self.handleSize
        b = self.boundingRect()
        self.handles[self.handleTopLeft] = QRectF(b.left(), b.top(), s, s)
        self.handles[self.handleTopMiddle] = QRectF(b.center().x() - s / 2, b.top(), s, s)
        self.handles[self.handleTopRight] = QRectF(b.right() - s, b.top(), s, s)
        self.handles[self.handleMiddleLeft] = QRectF(b.left(), b.center().y() - s / 2, s, s)
        self.handles[self.handleMiddleRight] = QRectF(b.right() - s, b.center().y() - s / 2, s, s)
        self.handles[self.handleBottomLeft] = QRectF(b.left(), b.bottom() - s, s, s)
        self.handles[self.handleBottomMiddle] = QRectF(b.center().x() - s / 2, b.bottom() - s, s, s)
        self.handles[self.handleBottomRight] = QRectF(b.right() - s, b.bottom() - s, s, s)

    def interactiveResize(self, mousePos):
        """
        Perform shape interactive resize.
        """
        offset = self.handleSize + self.handleSpace
        boundingRect = self.boundingRect()
        rect = self.rect()
        diff = QPointF(0, 0)

        self.prepareGeometryChange()

        if self.handleSelected == self.handleTopLeft:

            fromX = self.mousePressRect.left()
            fromY = self.mousePressRect.top()
            toX = fromX + mousePos.x() - self.mousePressPos.x()
            toY = fromY + mousePos.y() - self.mousePressPos.y()
            diff.setX(toX - fromX)
            diff.setY(toY - fromY)
            boundingRect.setLeft(toX)
            boundingRect.setTop(toY)
            rect.setLeft(boundingRect.left() + offset)
            rect.setTop(boundingRect.top() + offset)
            self.setRect(rect)

        elif self.handleSelected == self.handleTopMiddle:

            fromY = self.mousePressRect.top()
            toY = fromY + mousePos.y() - self.mousePressPos.y()
            diff.setY(toY - fromY)
            boundingRect.setTop(toY)
            rect.setTop(boundingRect.top() + offset)
            self.setRect(rect)

        elif self.handleSelected == self.handleTopRight:

            fromX = self.mousePressRect.right()
            fromY = self.mousePressRect.top()
            toX = fromX + mousePos.x() - self.mousePressPos.x()
            toY = fromY + mousePos.y() - self.mousePressPos.y()
            diff.setX(toX - fromX)
            diff.setY(toY - fromY)
            boundingRect.setRight(toX)
            boundingRect.setTop(toY)
            rect.setRight(boundingRect.right() - offset)
            rect.setTop(boundingRect.top() + offset)
            self.setRect(rect)

        elif self.handleSelected == self.handleMiddleLeft:

            fromX = self.mousePressRect.left()
            toX = fromX + mousePos.x() - self.mousePressPos.x()
            diff.setX(toX - fromX)
            boundingRect.setLeft(toX)
            rect.setLeft(boundingRect.left() + offset)
            self.setRect(rect)

        elif self.handleSelected == self.handleMiddleRight:
            print("MR")
            fromX = self.mousePressRect.right()
            toX = fromX + mousePos.x() - self.mousePressPos.x()
            diff.setX(toX - fromX)
            boundingRect.setRight(toX)
            rect.setRight(boundingRect.right() - offset)
            self.setRect(rect)

        elif self.handleSelected == self.handleBottomLeft:

            fromX = self.mousePressRect.left()
            fromY = self.mousePressRect.bottom()
            toX = fromX + mousePos.x() - self.mousePressPos.x()
            toY = fromY + mousePos.y() - self.mousePressPos.y()
            diff.setX(toX - fromX)
            diff.setY(toY - fromY)
            boundingRect.setLeft(toX)
            boundingRect.setBottom(toY)
            rect.setLeft(boundingRect.left() + offset)
            rect.setBottom(boundingRect.bottom() - offset)
            self.setRect(rect)

        elif self.handleSelected == self.handleBottomMiddle:

            fromY = self.mousePressRect.bottom()
            toY = fromY + mousePos.y() - self.mousePressPos.y()
            diff.setY(toY - fromY)
            boundingRect.setBottom(toY)
            rect.setBottom(boundingRect.bottom() - offset)
            self.setRect(rect)

        elif self.handleSelected == self.handleBottomRight:

            fromX = self.mousePressRect.right()
            fromY = self.mousePressRect.bottom()
            toX = fromX + mousePos.x() - self.mousePressPos.x()
            toY = fromY + mousePos.y() - self.mousePressPos.y()
            diff.setX(toX - fromX)
            diff.setY(toY - fromY)
            boundingRect.setRight(toX)
            boundingRect.setBottom(toY)
            rect.setRight(boundingRect.right() - offset)
            rect.setBottom(boundingRect.bottom() - offset)
            self.setRect(rect)

        self.updateHandlesPos()

    def shape(self):
        """
        Returns the shape of this item as a QPainterPath in local coordinates.
        """
        path = QPainterPath()
        path.addRect(self.rect())
        if self.isSelected():
            for shape in self.handles.values():
                path.addEllipse(shape)
        return path

    def paint(self, painter, option, widget=None):
        """
        Paint the node in the graphic view.
        """
        painter.setBrush(QBrush(QColor(255, 0, 0, 100)))
        painter.setPen(QPen(QColor(0, 0, 0), 1.0, Qt.SolidLine))
        painter.drawRect(self.rect())

        painter.setRenderHint(QPainter.Antialiasing)
        painter.setBrush(QBrush(QColor(255, 0, 0, 255)))
        painter.setPen(QPen(QColor(0, 0, 0, 255), 1.0, Qt.SolidLine, Qt.RoundCap, Qt.RoundJoin))
        for handle, rect in self.handles.items():
            if self.handleSelected is None or handle == self.handleSelected:
                painter.drawEllipse(rect)


def main():

    app = QApplication(sys.argv)

    grview = QGraphicsView()
    scene = QGraphicsScene()
    scene.setSceneRect(0, 0, 680, 459)

    scene.addPixmap(QPixmap('01.png'))
    grview.setScene(scene)

    item = GraphicsRectItem(0, 0, 300, 150)
    scene.addItem(item)

    grview.fitInView(scene.sceneRect(), Qt.KeepAspectRatio)
    grview.show()
    sys.exit(app.exec_())


if __name__ == '__main__':
    main()