如何制作漂亮的霓虹灯效果？

Question

我想通过控制光的力量来制作美丽多汁的霓虹灯效果。为此，我构建了这样的代码

import sys
from PyQt5.QtWidgets import (QRadioButton, QHBoxLayout, QButtonGroup, 
    QApplication, QGraphicsScene,QGraphicsView, QGraphicsLinearLayout, QGraphicsWidget, QWidget, QLabel)
from PyQt5.QtGui import QIcon, QPixmap
from PyQt5.QtCore import QSize, QPoint,Qt
from PyQt5 import QtCore, QtGui, QtWidgets
from PyQt5.QtWidgets import *



from PyQt5.QtGui import QPainter


class Window(QWidget):
    def __init__(self):
        super().__init__()

        self.resize(800, 800)

        self.setStyleSheet('background:black;')


        mainLayout = QtWidgets.QVBoxLayout(self)
        mainLayout.setContentsMargins(0, 0, 0, 0)

        color_1 = '162, 162, 162,'
        color_2 = '255, 255, 255,'
        color_3 = '0, 255, 255,'

        d_ = 1

        power = int(255/100*d_)

        for x in range(6):
            label = QLabel(self)


            color_L = color_1
            glass_L = 255
            size_L = 60
            blut_L = 0


            label.raise_()

            if x < 1 :
                color_L = color_1
            elif x < 2 :
                color_L = color_3
                glass_L = power
            elif x < 3 :
                color_L = color_2
                blut_L = 6
                glass_L = power
            elif x < 4:
                color_L = color_2
                blut_L = 40
                glass_L = power
            elif x < 5 :
                label.lower()
                color_L = color_3
                blut_L = 40
                size_L = 70
                glass_L = power
            elif x < 6 :
                label.lower()
                color_L = color_3
                blut_L = 150
                size_L = 70
                glass_L = power

            label.setText('test')
            label.setStyleSheet('background:rgba(0, 0, 0, 0);color:rgba({} {}); font-size:{}px;'.format(color_L, glass_L,size_L))
            label.resize(self.width(), self.height())
            label.setAlignment(Qt.AlignCenter)

            self.effect = QtWidgets.QGraphicsBlurEffect(blurRadius=blut_L)
            label.setGraphicsEffect(self.effect)

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

但是代码太麻烦了。而且结果证明这太不自然了，

如果您指示弱的光强度，则看起来特别糟糕。

有没有更好的选择可以产生霓虹灯效果？还是为什么他看起来这么糟糕？

Answer 1

嗯，我最终认为这样做很有趣：-）

重要：考虑到这是某种形式的破解，因为它使用了Qt的private和未记录的功能（与QGraphicsBlurEffect所使用的功能相同），并且不能保证它可以在任何地方使用。我已经能够通过从实时电视查看器中借用一些称为Atropine的代码来实现此目标，有趣的部分位于effects.py源中。

[请注意，通过在QGraphicsEffect自身内使用私有QGraphicsScene的“抽象”绘图可能会实现类似的效果，但是它会慢得多（因为每次draw()方法都必须创建新的QGraphicsPixmapItems的效果被称为），并且可能会有一些副作用。

诀窍是通过ctypes获得函数名称，我只能在Linux和Windows中找到导出的函数名称（但是我无法在那里进行测试）：

＃Linux：$ nm -D /usr/lib/libQt5Widgets.so | grep qt_blurImage004adc30 T _ Z12qt_blurImageP8QPainterR6QImagedbbi004ae0e0 T _Z12qt_blurImageR6QImagedbi＃Windows（通过Mingw）：> objdump -p /QtGui4.dll | grep blurImage[8695]？qt_blurImage @@ YAXAAVQImage @@ N_NH @ Z[8696] ？qt_blurImage @@ YAXPAVQPainter @@ AAVQImage @@ N_N2H @ Z

我无法对MacO进行测试，但我认为它应该与Linux上的命令行相同。

[注意，这些函数名在相同的操作系统和 Qt版本上似乎是静态的：我在Qt4的旧nn文件上运行相同的libQtGui.so命令，并且得到相同的结果。] >

所以，这就是您的美丽的霓虹灯效果

...

这是代码，我添加了一个示例程序对其进行测试：

import sys
import sip
import ctypes
from PyQt5 import QtCore, QtGui, QtWidgets

if sys.platform == 'win32':
    # the exported function name has illegal characters on Windows, let's use
    # getattr to access it
    _qt_blurImage  = getattr(ctypes.CDLL('QtGui5.dll'), 
        '?qt_blurImage@@YAXPAVQPainter@@AAVQImage@@N_N2H@Z')
else:
    try:
        qtgui = ctypes.CDLL('libQt5Widgets.so')
    except:
        qtgui = ctypes.CDLL('libQt5Widgets.so.5')
    _qt_blurImage = qtgui._Z12qt_blurImageP8QPainterR6QImagedbbi


class NeonEffect(QtWidgets.QGraphicsColorizeEffect):
    _blurRadius = 5.
    _glow = 2

    def glow(self):
        return self._glow

    @QtCore.pyqtSlot(int)
    def setGlow(self, glow):
        if glow == self._glow:
            return
        self._glow = max(1, min(glow, 10))
        self.update()

    def blurRadius(self):
        return self._blurRadius

    @QtCore.pyqtSlot(int)
    @QtCore.pyqtSlot(float)
    def setBlurRadius(self, radius):
        if radius == self._blurRadius:
            return
        self._blurRadius = max(1., float(radius))
        self.update()

    def applyBlurEffect(self, blurImage, radius, quality, alphaOnly, transposed=0, qp=None):
        blurImage = ctypes.c_void_p(sip.unwrapinstance(blurImage))
        radius = ctypes.c_double(radius)
        quality = ctypes.c_bool(quality)
        alphaOnly = ctypes.c_bool(alphaOnly)
        transposed = ctypes.c_int(transposed)
        if qp:
            qp = ctypes.c_void_p(sip.unwrapinstance(qp))
        _qt_blurImage(qp, blurImage, radius, quality, alphaOnly, transposed)

    def draw(self, qp):
        pm, offset = self.sourcePixmap(QtCore.Qt.LogicalCoordinates, self.PadToEffectiveBoundingRect)
        if pm.isNull():
            return

        # use a double sized image to increase the blur factor
        scaledSize = QtCore.QSize(pm.width() * 2, pm.height() * 2)
        blurImage = QtGui.QImage(scaledSize, QtGui.QImage.Format_ARGB32_Premultiplied)
        blurImage.fill(0)
        blurPainter = QtGui.QPainter(blurImage)
        blurPainter.drawPixmap(0, 0, pm.scaled(scaledSize, 
            QtCore.Qt.KeepAspectRatio, QtCore.Qt.SmoothTransformation))
        blurPainter.end()

        # apply the blurred effect on the image
        self.applyBlurEffect(blurImage, 1 * self._blurRadius, True, False)

        # start the painter that will use the previous image as alpha
        tmpPainter = QtGui.QPainter(blurImage)
        # using SourceIn composition mode we use the existing alpha values
        # to paint over
        tmpPainter.setCompositionMode(tmpPainter.CompositionMode_SourceIn)
        color = QtGui.QColor(self.color())
        color.setAlpha(color.alpha() * self.strength())
        # fill using the color
        tmpPainter.fillRect(pm.rect(), color)
        tmpPainter.end()

        # repeat the effect which will make it more "glowing"
        for g in range(self._glow):
            qp.drawImage(0, 0, blurImage.scaled(pm.size(), 
                QtCore.Qt.KeepAspectRatio, QtCore.Qt.SmoothTransformation))

        super().draw(qp)


class NeonTest(QtWidgets.QWidget):
    def __init__(self):
        super().__init__()
        layout = QtWidgets.QGridLayout(self)

        palette = self.palette()
        palette.setColor(palette.Window, QtCore.Qt.black)
        palette.setColor(palette.WindowText, QtCore.Qt.white)
        self.setPalette(palette)


        self.label = QtWidgets.QLabel('NEON EFFECT')
        layout.addWidget(self.label, 0, 0, 1, 2)
        self.label.setPalette(QtWidgets.QApplication.palette())
        self.label.setContentsMargins(20, 20, 20, 20)
        f = self.font()
        f.setPointSizeF(48)
        f.setBold(True)
        self.label.setFont(f)
        self.effect = NeonEffect(color=QtGui.QColor(152, 255, 250))
        self.label.setGraphicsEffect(self.effect)
        self.effect.setBlurRadius(40)

        layout.addWidget(QtWidgets.QLabel('blur radius'))
        radiusSpin = QtWidgets.QDoubleSpinBox(minimum=1, maximum=100, singleStep=5)
        layout.addWidget(radiusSpin, 1, 1)
        radiusSpin.setValue(self.effect.blurRadius())
        radiusSpin.valueChanged.connect(self.effect.setBlurRadius)

        layout.addWidget(QtWidgets.QLabel('glow factor'))
        glowSpin = QtWidgets.QSpinBox(minimum=1, maximum=10)
        layout.addWidget(glowSpin, 2, 1)
        glowSpin.setValue(self.effect.glow())
        glowSpin.valueChanged.connect(self.effect.setGlow)

        layout.addWidget(QtWidgets.QLabel('color strength'))
        strengthSpin = QtWidgets.QDoubleSpinBox(minimum=0, maximum=1, singleStep=.05)
        strengthSpin.setValue(1)
        layout.addWidget(strengthSpin, 3, 1)
        strengthSpin.valueChanged.connect(self.effect.setStrength)

        colorBtn = QtWidgets.QPushButton('color')
        layout.addWidget(colorBtn, 4, 0)
        colorBtn.clicked.connect(self.setColor)

        self.aniBtn = QtWidgets.QPushButton('play animation')
        layout.addWidget(self.aniBtn, 4, 1)
        self.aniBtn.setCheckable(True)

        self.glowAni = QtCore.QVariantAnimation(duration=250)
        self.glowAni.setStartValue(1)
        self.glowAni.setEndValue(5)
        self.glowAni.setEasingCurve(QtCore.QEasingCurve.InQuad)
        self.glowAni.valueChanged.connect(glowSpin.setValue)
        self.glowAni.finished.connect(self.animationFinished)

        self.aniBtn.toggled.connect(self.glowAni.start)

    def animationFinished(self):
        if self.aniBtn.isChecked():
            self.glowAni.setDirection(not self.glowAni.direction())
            self.glowAni.start()

    def setColor(self):
        d = QtWidgets.QColorDialog(self.effect.color(), self)
        if d.exec_():
            self.effect.setColor(d.currentColor())
请注意，根据我的测试，使用大于1的辉光因数且模糊半径小于4的辉光因数可能会导致某些绘画伪影。

我已经能够在两台Linux机器（Qt 5.7和5.12）上成功测试它，如果有人愿意评论在其他平台上的测试，我会很乐意相应地更新此答案。