未正确旋转图像

Question

我正在尝试旋转 QGraphicsView 对象的背景，但遇到了麻烦。红笔描述了我遇到的问题。

我想要的是：

• 我想让箭头保持在屏幕中间的中心位置。

• 我希望背景图像以屏幕中心为参考旋转

• 我想在 QGraphicsView 中定义一个矩形。这将被定义为界定显示内容的区域。因此，每次我旋转屏幕时。图像“未覆盖”的区域始终位于矩形边界之外。

• 我想在屏幕中间定义旋转参考点（x=VIEW_WIDTH/2，y=VIEW_HEIGHT/2）

这是我的代码：

首先，我将显示箭头类：

from PyQt5 import QtCore, QtGui, QtWidgets # importation of some libraries 

# Construnction of an arrow item, it'll be used in the QGraphicsView 

class ArrowItem(QtWidgets.QGraphicsPathItem): # it inherit QgraphicsPathItem, which allows to handle it 

# in the QgraphicsView

    def __init__(self, parent=None): # The init method

        super().__init__(parent)

        self._length = -1

        self._angle = 0

        self._points = QtCore.QPointF(), QtCore.QPointF(), QtCore.QPointF() # with three points we 

# construct a triangle. 

        self.length = 40.0 # the basic triangle length 

        self.rotate(180) # the triangle was built upside down, though I've just ran the function 'rotate'

    @property

    def angle(self):

        """

        angle of the arrow

        :return:

        """

        return self._angle

    @angle.setter

    def angle(self, angle):

        self._angle = angle

    @property

    def length(self):

        return self._length

    @length.setter

    def length(self, l):

        self._length = l

        pos_top = QtCore.QPointF(0, l * 4 / 5)

        pos_left = QtCore.QPointF(-l * 3 / 5, -l / 5)

        pos_right = QtCore.QPointF(

            l * 3 / 5,

            -l / 5,

        )

        path = QtGui.QPainterPath()

        path.moveTo(pos_top)

        path.lineTo(pos_right)

        path.lineTo(pos_left)

        self.setPath(path)

        self._points = pos_top, pos_left, pos_right

    def paint(self, painter, option, widget):

        pos_top, pos_left, pos_right = self._points

        left_color = QtGui.QColor("#cc0000")

        right_color = QtGui.QColor("#ff0000")

        bottom_color = QtGui.QColor("#661900")

Answer 1

如果你想旋转一个QGraphicsItem，没有必要使用QTransform，只需使用setRotation方法即可。另一方面，必须对图像进行缩放，以便与可见区域相交的旋转区域与可见区域相同，并且最小区域计算如下：sqrt(2) x max(width, height)。综合以上情况，解决方案是：from PyQt5 import QtCore, QtGui, QtWidgetsclass ArrowItem(QtWidgets.QGraphicsPathItem):    def __init__(self, parent=None):        super().__init__(parent)        self._length = -1        self._points = (            QtCore.QPointF(),            QtCore.QPointF(),            QtCore.QPointF(),        )        self.length = 40.0    @property    def length(self):        return self._length    @length.setter    def length(self, l):        self._length = l        pos_top = QtCore.QPointF(0, l * 4 / 5)        pos_left = QtCore.QPointF(-l * 3 / 5, -l / 5)        pos_right = QtCore.QPointF(            l * 3 / 5,            -l / 5,        )        path = QtGui.QPainterPath()        path.moveTo(pos_top)        path.lineTo(pos_right)        path.lineTo(pos_left)        self.setPath(path)        self._points = pos_top, pos_left, pos_right    def paint(self, painter, option, widget):        pos_top, pos_left, pos_right = self._points        left_color = QtGui.QColor("#cc0000")        right_color = QtGui.QColor("#ff0000")        bottom_color = QtGui.QColor("#661900")        path_left = QtGui.QPainterPath()        path_left.lineTo(pos_top)        path_left.lineTo(pos_left)        path_right = QtGui.QPainterPath()        path_right.lineTo(pos_top)        path_right.lineTo(pos_right)        path_bottom = QtGui.QPainterPath()        path_bottom.lineTo(pos_left)        path_bottom.lineTo(pos_right)        painter.setPen(QtGui.QColor("black"))        painter.setBrush(left_color)        painter.drawPath(path_left)        painter.setBrush(right_color)        painter.drawPath(path_right)        painter.setBrush(bottom_color)        painter.drawPath(path_bottom)    def moveTo(self, next_position, duration=100):        self._animation = QtCore.QVariantAnimation()        self._animation.setStartValue(self.pos())        self._animation.setEndValue(next_position)        self._animation.setDuration(duration)        self._animation.start(QtCore.QAbstractAnimation.DeleteWhenStopped)        self._animation.valueChanged.connect(self.setPos)class MainWindow(QtWidgets.QMainWindow):    VIEW_HEIGHT = 600    VIEW_WIDTH = 900    def __init__(self, parent=None):        super().__init__(parent)        self.scene = QtWidgets.QGraphicsScene(self)        self.view = QtWidgets.QGraphicsView(self.scene)        self.status_btn = QtWidgets.QPushButton("Status")        self.settings_btn = QtWidgets.QPushButton("Settings")        self.analyze_btn = QtWidgets.QPushButton("Analyze")        self.field_btn = QtWidgets.QPushButton("Field")        self.guide_btn = QtWidgets.QPushButton("Guide")        self.mapping_btn = QtWidgets.QPushButton("Mapping")        central_widget = QtWidgets.QWidget()        self.setCentralWidget(central_widget)        vlayl = QtWidgets.QVBoxLayout()        vlayl.addWidget(self.status_btn)        vlayl.addWidget(self.settings_btn)        vlayl.addWidget(self.analyze_btn)        vlayr = QtWidgets.QVBoxLayout()        vlayr.addWidget(self.field_btn)        vlayr.addWidget(self.guide_btn)        vlayr.addWidget(self.mapping_btn)        hlay = QtWidgets.QHBoxLayout(central_widget)        hlay.addLayout(vlayl)        hlay.addWidget(self.view)        hlay.addLayout(vlayr)        self.status_btn.clicked.connect(self.rotate_arrow)        self.guide_btn.clicked.connect(self.rotate_pixmap)        self.view.setFixedSize(self.VIEW_WIDTH, self.VIEW_HEIGHT)        r = self.view.mapToScene(self.view.viewport().rect()).boundingRect()        self.view.setSceneRect(r)        factor = 1.5 * max(self.VIEW_WIDTH, self.VIEW_HEIGHT)        pixmap = QtGui.QPixmap("ola.png").scaled(factor, factor)        self.pixmap_item = self.scene.addPixmap(pixmap)        center = self.pixmap_item.boundingRect().center()        self.pixmap_item.setPos(-center)        self.pixmap_item.setTransformOriginPoint(center)        self.arrow_item = ArrowItem()        self.scene.addItem(self.arrow_item)    def rotate_arrow(self):        delta = 30.0        self.arrow_item.setRotation(self.arrow_item.rotation() + delta)    def rotate_pixmap(self):        delta = 15.0        self.pixmap_item.setRotation(self.pixmap_item.rotation() + delta)        self.arrow_item.setRotation(self.arrow_item.rotation() + delta)if __name__ == "__main__":    import sys    app = QtWidgets.QApplication(sys.argv)    w = MainWindow()    w.show()    sys.exit(app.exec_())