列印影象是影象處理軟體中的一個常用功能。列印影象實際上是在QPaintDevice中畫圖，與平常在QWidget、QPixmap和QImage中畫圖一樣，都是建立一個QPainter物件進行畫圖的，只是列印使用的是QPrinter，它本質上也是一個QPaintDevice（繪圖裝置）。

案例37 QPrinter的使用

import sys
from PyQt5.QtWidgets import QMainWindow, QApplication, QLabel, QSizePolicy, QAction
from PyQt5.QtGui import QIcon, QImage, QPixmap, QPainter
 
from PyQt5.QtPrintSupport import QPrinter, QPrintDialog
from PyQt5.QtCore import Qt


class QPrinterDemo(QMainWindow):
    def __init__(self, parent=None):
        super().__init__(parent)
        self.setWindowTitle(self.tr("列印圖片"))
        self.imageLabel = QLabel()
        self.imageLabel.setSizePolicy(QSizePolicy.Ignored, QSizePolicy.Ignored)
        self.setCentralWidget(self.imageLabel)

        self.image 
 
= QImage()
        self.createActions()
        self.createMenus()
        self.createToolBars()

        if self.image.load("./images/screen.png"):
            self.imageLabel.setPixmap(QPixmap.fromImage(self.image))
            self.resize(self.image.width(), self.image.height())

    def createActions(self):
        self.PrintAction 
 
= QAction(
            QIcon("./images/printer.png"),
            self.tr("列印"),
            self
        )
        self.PrintAction.setShortcut("Ctrl+P")
        self.PrintAction.setStatusTip(self.tr("列印"))
        self.PrintAction.triggered.connect(self.slotPrint)

    def createMenus(self):
        PrintMenu = self.menuBar().addMenu(self.tr("列印"))
        PrintMenu.addAction(self.PrintAction)

    def createToolBars(self):
        fileToolBar = self.addToolBar("Print")
        fileToolBar.addAction(self.PrintAction)

    def slotPrint(self):
        printer = QPrinter()
        printDialog = QPrintDialog(printer, self)
        if printDialog.exec_():
            painter = QPainter(printer)
            rect = painter.viewport()
            size = self.image.size()
            size.scale(rect.size(), Qt.KeepAspectRatio)
            painter.setViewport(rect.x(), rect.y(), size.width(), size.height())
            painter.setWindow(self.image.rect())
            painter.drawImage(0, 0, self.image)


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