python - QPaint 使用 mouseevent 进行平移缩放

Question

我需要绘制一个带有缩放和Qwheel事件的形状。我尝试过painter.scale和painter.translate，但它根本不影响形状的缩放。

这个想法是绘制不同的形状，例如下图上的这个，一个起始值为( 200, 300) 的矩形 看起来很完美，甚至以 canvas 小部件 为中心。但当值较大时( 500, 700 )，如下图第二个所示，会放大并变得不需要。我想按比例绘制它，并能够使用鼠标事件来滚动(放大和缩小)它。

可视化。

代码:

import sys
from PyQt5 import QtCore, QtGui, QtWidgets

class Foo(QtWidgets.QWidget):
    def __init__(self, parent=None):
        super(Foo, self).__init__(parent)
        self.setGeometry(QtCore.QRect(200, 100, 700, 600))        
        self.paint = Paint()
        self.sizeHint()
        self.lay = QtWidgets.QVBoxLayout()
        self.lay.addWidget(self.paint)
        self.setLayout(self.lay)

class Paint(QtWidgets.QWidget):
    def __init__(self, parent=None):
        super(Paint, self).__init__(parent)
        self.setBackgroundRole(QtGui.QPalette.Base)     
        self.setAutoFillBackground(True)
        self._width = 200
        self._height = 300


    def paintEvent(self, event):
        pen = QtGui.QPen()
        brush = QtGui.QBrush( QtCore.Qt.darkCyan, QtCore.Qt.Dense5Pattern)
        painter = QtGui.QPainter(self)
        painter.setRenderHint(QtGui.QPainter.Antialiasing)
        painter.setPen(pen)
        painter.setBrush(brush)
        r = QtCore.QRect(QtCore.QPoint((self.width() - self._width)/ 2, (self.height() -self._height)/ 2), QtCore.QSize(self._width, self._height))
        painter.drawRect(r)
        painter.scale(0.4,0.4)
        painter.translate(50, 50)


if __name__ == '__main__':
    app = QtWidgets.QApplication(sys.argv)
    w = Foo()
    w.show()
    sys.exit(app.exec_())

我非常感谢任何帮助。谢谢

Answer 1

比例是相对于左上角给出的，因此如果我们希望它相对于中心进行缩放，则必须首先将其移动到那里，然后在缩放后将其放置在初始位置。对于比例因子的情况，请使用带有 angleDelta() 的 wheelEvent 方法，并乘以适当的因子。

import sys
from PyQt5 import QtCore, QtGui, QtWidgets

class Foo(QtWidgets.QWidget):
    def __init__(self, parent=None):
        super(Foo, self).__init__(parent)
        self.setGeometry(QtCore.QRect(200, 100, 700, 600))        
        self.paint = Paint()
        self.sizeHint()
        self.lay = QtWidgets.QVBoxLayout()
        self.lay.addWidget(self.paint)
        self.setLayout(self.lay)

class Paint(QtWidgets.QWidget):
    def __init__(self, parent=None):
        super(Paint, self).__init__(parent)
        self.setBackgroundRole(QtGui.QPalette.Base)     
        self.setAutoFillBackground(True)
        self.r = QtCore.QRect(QtCore.QPoint(), QtCore.QSize(200, 300))
        self._factor = 1.0

    def paintEvent(self, event):
        self.r.moveCenter(self.rect().center())
        pen = QtGui.QPen()
        brush = QtGui.QBrush( QtCore.Qt.darkCyan, QtCore.Qt.Dense5Pattern)
        painter = QtGui.QPainter(self)
        painter.setBrush(brush)
        painter.setPen(pen)
        painter.setRenderHint(QtGui.QPainter.Antialiasing)

        painter.translate(self.rect().center())
        painter.scale(self._factor, self._factor)
        painter.translate(-self.rect().center())

        painter.drawRect(self.r)

    def wheelEvent(self, event):
        self._factor *= 1.01**(event.angleDelta().y()/15.0)
        self.update()
        super(Paint, self).wheelEvent(event)


if __name__ == '__main__':
    app = QtWidgets.QApplication(sys.argv)
    w = Foo()
    w.show()
    sys.exit(app.exec_())