QPaint 平移缩放与 mouseevent

Question

我需要用缩放和Qwheel event 绘制一个形状。我试过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，一个矩形形状，起始值为(200, 300) 看起来很完美，甚至以canvas widget 为中心。但当 (500, 700) 值较大时，如 第二个下图 所示会放大并变得不需要。我想用mouse event 来按比例绘制它并能够（放大和缩小）。

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，所以如果我们希望它相对于中心进行缩放，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，使用wheelEvent 方法，使用angleDelta()，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_())