关于QPixmap改变不透明度

Question

我在QLabel上有一个QPixmap，QLabel是黄色的，问题是 我只是想改变QPixmap颜色的不透明度，有没有办法解决这个问题。在

from PyQt5.QtWidgets import QApplication, QLabel
from PyQt5.QtGui import QPixmap
from PyQt5.QtCore import Qt
import sys

class Pixmap(QPixmap):
    def __init__(self):
        super().__init__(700, 400)
        self.fill(Qt.yellow)

class Drawing(QLabel):
    def __init__(self):
        super().__init__()
        pix = Pixmap()
        self.setPixmap(pix)

if __name__ == "__main__":
    app = QApplication(sys.argv)
    draw = Drawing()
    draw.show()
    sys.exit(app.exec_())

Answer 1

您必须创建一个新的QPixmap，并使用原始的QPixmap绘制它，QPainter设置不透明度：

from PyQt5 import QtCore, QtGui, QtWidgets


class Widget(QtWidgets.QWidget):
    def __init__(self, parent=None):
        super().__init__()

        self.m_original_pixmap = QtGui.QPixmap(700, 400)
        self.m_original_pixmap.fill(QtCore.Qt.yellow)

        self.m_slider = QtWidgets.QSlider(
            QtCore.Qt.Horizontal,
            minimum=0,
            maximum=100,
            value=100,
            valueChanged=self.onValueChanged,
        )
        self.m_label = QtWidgets.QLabel(alignment=QtCore.Qt.AlignCenter)
        self.m_label.setPixmap(self.m_original_pixmap)

        lay = QtWidgets.QVBoxLayout(self)
        lay.addWidget(self.m_slider)
        lay.addWidget(self.m_label)

    @QtCore.pyqtSlot(int)
    def onValueChanged(self, value):
        new_pix = QtGui.QPixmap(self.m_original_pixmap.size())
        new_pix.fill(QtCore.Qt.transparent)
        painter = QtGui.QPainter(new_pix)
        painter.setOpacity(value * 0.01)
        painter.drawPixmap(QtCore.QPoint(), self.m_original_pixmap)
        painter.end()
        self.m_label.setPixmap(new_pix)


if __name__ == "__main__":
    import sys

    app = QtWidgets.QApplication(sys.argv)
    draw = Widget()
    draw.show()
    sys.exit(app.exec_())