PyQt5 颜色对话框QColorDialog

PyQt5是Python编程语言和Qt库的集成。它能够帮助Python程序员编写跨平台GUI应用程序，具有强大的图形用户界面（GUI）工具包。在PyQt5中，通过使用QColorDialog类，可以实现对话框的显示并选择颜色。

以下是PyQt5的“QColorDialog”的详细使用攻略：

1. 导入库

首先，要在Python代码中导入“QtCore”和“QtGui”库，以使用QColorDialog。

from PyQt5 import QtCore, QtGui

2. 创建QColorDialog

要创建QColorDialog实例，可以使用“QColorDialog()”，以显示一个包含“默认颜色”按钮的对话框。

color_dialog = QtWidgets.QColorDialog()

3. 显示对话框

要显示QColorDialog对话框，请使用“exec_()”函数。

color = color_dialog.exec_()

4. 获取颜色

一旦对话框退出，就会获取所选的颜色。可以使用“color()”方法获取颜色。

selected_color = color_dialog.selectedColor().name()

在这里有一个示例代码，显示如何使用QColorDialog：

from PyQt5 import QtCore, QtGui, QtWidgets

class Example(QtWidgets.QWidget):

    def __init__(self):
        super().__init__()

        self.initUI()

    def initUI(self):

        self.setWindowTitle('Color Dialog')

        vbox = QtWidgets.QVBoxLayout(self)
        btn = QtWidgets.QPushButton('Dialog', self)
        btn.move(20, 20)
        vbox.addWidget(btn)
        btn.clicked.connect(self.showDialog)
        self.lbl = QtWidgets.QLabel('Knowledge helps to make a good man.', self)
        self.lbl.move(130, 20)
        vbox.addWidget(self.lbl)

        self.setGeometry(300, 300, 290, 150)

    def showDialog(self):

        color = QtWidgets.QColorDialog.getColor()

        if color.isValid():
            self.lbl.setStyleSheet('QWidget { background-color: %s}' % color.name())

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

在这个示例中，单击打开一个颜色对话框，当用户选择一个颜色之后，程序会将背景色设置为所选颜色。

接下来，我们将看到一个更复杂的示例，其中使用了QGradientPicker和QFileDialog选择并应用颜色渐变到图像文件。

from PyQt5.QtCore import Qt
from PyQt5.QtGui import QImage, QPalette, QPixmap
from PyQt5.QtWidgets import (QApplication, QColorDialog, QFileDialog,
                             QFrame, QGraphicsScene, QGraphicsView, QHBoxLayout, QLabel,
                             QPushButton, QSizePolicy, QVBoxLayout, QWidget)


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

        self.image = QImage()
        self.modified_image = QImage()

        self.create_widgets()
        self.create_layout()

        self.setWindowTitle("Image Viewer")
        self.resize(700, 500)

    def create_widgets(self):
        self.color1_button = QPushButton()
        self.color1_button.setStyleSheet("background-color: transparent")
        self.color1_button.setIcon(self.create_colored_icon())
        self.color1_button.clicked.connect(self.pick_color_1)

        self.color2_button = QPushButton()
        self.color2_button.setStyleSheet("background-color: transparent")
        self.color2_button.setIcon(self.create_colored_icon())
        self.color2_button.clicked.connect(self.pick_color_2)

        self.load_button = QPushButton("Load Image")
        self.load_button.clicked.connect(self.load_image)

        self.save_button = QPushButton("Save Image")
        self.save_button.clicked.connect(self.save_image)

        self.quit_button = QPushButton("Quit")
        self.quit_button.clicked.connect(self.close)

        self.view = QGraphicsView()
        self.view.setRenderHints(QPainter.Antialiasing | QPainter.SmoothPixmapTransform)
        self.view.setViewportUpdateMode(QGraphicsView.FullViewportUpdate)

        self.scene = QGraphicsScene(self)
        self.scene.setSceneRect(self.view.rect())
        self.view.setScene(self.scene)

    def create_colored_icon(self):
        size = 128
        pixmap = QPixmap(size, size)
        pixmap.fill(Qt.black)
        painter = QtGui.QPainter(pixmap)
        gradient = QtGui.QLinearGradient(0, 0, size, size)
        gradient.setColorAt(0, QtGui.QColor(50, 50, 50))
        gradient.setColorAt(1, QtGui.QColor(200, 200, 200))
        painter.setBrush(QtGui.QBrush(gradient))
        painter.drawRect(0, 0, size, size)

        return QIcon(pixmap)

    def create_layout(self):
        top_layout = QHBoxLayout()
        top_layout.addWidget(QLabel("Color 1:"))
        top_layout.addWidget(self.color1_button)
        top_layout.addWidget(QLabel("Color 2:"))
        top_layout.addWidget(self.color2_button)
        top_layout.addStretch()
        top_layout.addWidget(self.load_button)
        top_layout.addWidget(self.save_button)
        top_layout.addWidget(self.quit_button)

        bottom_layout = QVBoxLayout()
        bottom_layout.addWidget(self.view)

        main_layout = QVBoxLayout(self)
        main_layout.addLayout(top_layout)
        main_layout.addLayout(bottom_layout)

    def load_image(self):
        file_name, _ = QFileDialog.getOpenFileName(self, "Open Image", "",
                                                   "Images (*.png *.xpm *.jpg *.bmp)")
        if not file_name:
            return

        self.image.load(file_name)

        self.modified_image = QImage(self.image.size(), self.image.format())
        self.modified_image.fill(Qt.white)

        self.show_image()

    def save_image(self):
        file_name, _ = QFileDialog.getSaveFileName(self, "Save Image", "",
                                                   "Images (*.png *.xpm *.jpg *.bmp)")
        if not file_name:
            return

        self.modified_image.save(file_name)

    def show_image(self):
        if self.image.isNull():
            pixmap = QPixmap()
        else:
            pixmap = QPixmap.fromImage(self.modified_image)

        self.scene.clear()
        self.scene.addPixmap(pixmap)

    def pick_color_1(self):
        color = QColorDialog.getColor()

        if not color.isValid():
            return

        self.color1_button.setStyleSheet(f"background-color: {color.name()}")
        self.fill_modified_image()

    def pick_color_2(self):
        color = QColorDialog.getColor()

        if not color.isValid():
            return

        self.color2_button.setStyleSheet(f"background-color: {color.name()}")
        self.fill_modified_image()

    def fill_modified_image(self):
        gradient = QtGui.QLinearGradient(0, 0, self.modified_image.width(), self.modified_image.height())
        gradient.setColorAt(0, QColor(self.color1_button.palette().button().color()))
        gradient.setColorAt(1, QColor(self.color2_button.palette().button().color()))

        painter = QtGui.QPainter(self.modified_image)
        painter.fillRect(self.modified_image.rect(), gradient)
        painter.end()

        self.show_image()


if __name__ == "__main__":
    import sys

    app = QApplication(sys.argv)
    palette = QPalette()
    palette.setColor(QPalette.Window, Qt.white)
    app.setPalette(palette)
    window = ImageViewer()
    window.show()
    sys.exit(app.exec_())

以上是“PyQt5 颜色对话框QColorDialog”的使用攻略及两个示例。在开发PyQt5 GUI应用程序时，使用QColorDialog可以方便地允许用户选择颜色，并将所选颜色应用到GUI元素中。