PyQT5 图片查看器

一款简易的图片查看器。由官方PyQt4 demo升级为PyQt5版本，原本只有缩放功能，现另加入打印和拖放功能。

#!/usr/bin/env python
from PyQt5 import QtCore, QtGui,QtWidgets
from PyQt5.QtPrintSupport import QPrinter, QPrintDialog,QPrintPreviewDialog

class ImageViewer(QtWidgets.QMainWindow):
    def __init__(self):
        super(ImageViewer, self).__init__()
        self.imageLabel = QtWidgets.QLabel()
        self.imageLabel.setAlignment(QtCore.Qt.AlignRight|QtCore.Qt.AlignVCenter)
        self.imageLabel.setBackgroundRole(QtGui.QPalette.Dark)
        self.imageLabel.setSizePolicy(QtWidgets.QSizePolicy.Ignored,QtWidgets.QSizePolicy.Ignored)
        #self.imageLabel.setSizePolicy(QtWidgets.QSizePolicy.Maximum,QtWidgets.QSizePolicy.Maximum)
        self.imageLabel.setScaledContents(True)
        self.scrollArea = QtWidgets.QScrollArea()
        self.scrollArea.setBackgroundRole(QtGui.QPalette.Dark)
        self.scrollArea.setWidget(self.imageLabel)
        self.setCentralWidget(self.scrollArea)
        self.createActions()
        self.createMenus()
       
        self.setAcceptDrops(True)#
       
        self.setWindowTitle("Image Viewer")
        self.resize(500, 400)
    
    def open(self):
        fileName,filetype = QtWidgets.QFileDialog.getOpenFileName(self, "Open File",
                QtCore.QDir.currentPath())
        if fileName:
            image = QtGui.QImage(fileName)
            if image.isNull():
                QtWidgets.QMessageBox.information(self, "Image Viewer",
                        "Cannot load %s." % fileName)
                return
            self.imageLabel.setPixmap(QtGui.QPixmap.fromImage(image))
            self.scaleFactor = 1.0
            self.printAct.setEnabled(True)
            self.fitToWindowAct.setEnabled(True)
            self.updateActions()
            if not self.fitToWindowAct.isChecked():
                self.imageLabel.adjustSize()
    
    def dragEnterEvent(self, event):#拖动开始时，以及刚进入目标控件时调用
        event.acceptProposedAction() #必须要有
    
    def dropEvent(self, event):
        if event.mimeData().hasUrls():
            urls=event.mimeData().urls()
            try:
                url=urls[0]
                fileName = str(url.toLocalFile())
                if fileName:
                    image = QtGui.QImage(fileName)
                    if image.isNull():
                        QtWidgets.QMessageBox.information(self, "Image Viewer",
                                "Cannot load %s." % fileName)
                        return
                    self.imageLabel.setPixmap(QtGui.QPixmap.fromImage(image))
                    self.scaleFactor = 1.0
                    self.printAct.setEnabled(True)
                    self.fitToWindowAct.setEnabled(True)
                    self.updateActions()
                    if not self.fitToWindowAct.isChecked():
                        self.imageLabel.adjustSize()
            except:
                pass
        else:
            super(ImageViewer, self).dropEvent(event)
    
    def handlePrint(self, printer):#打印
        painter = QtGui.QPainter(printer)#使用painter 绘制文字、pixmap等在printer上
        painter.setRenderHint(QtGui.QPainter.Antialiasing)#抗锯齿#可有可无
        pix = self.imageLabel.pixmap()
        size = self.scaleFactor * pix.size()
        painter.drawPixmap(0, 0, size.width(), size.height(),pix)
       
    def printPreview(self):#打印预览
        dialog = QPrintPreviewDialog()
        dialog.paintRequested.connect(self.handlePrint)
        dialog.exec_()
 
    def print_setup(self):#打印，无预览
        printer = QPrinter()
        painter.setRenderHint(QPainter.Antialiasing)#抗锯齿
        dialog = QPrintDialog(printer, self)
        if dialog.exec_() == QDialog.Accepted:
            self.handlePrint(printer)

    def zoomIn(self):
        self.scaleImage(1.25)
        
    def zoomOut(self):
        self.scaleImage(0.8)
        
    def normalSize(self):
        self.imageLabel.adjustSize()
        self.scaleFactor = 1.0
        
    def fitToWindow(self):
        fitToWindow = self.fitToWindowAct.isChecked()
        self.scrollArea.setWidgetResizable(fitToWindow)
        if not fitToWindow:
            self.normalSize()
        self.updateActions()
        
    def about(self):
        QtWidgets.QMessageBox.about(self, "About Image Viewer",
                "<p>The <b>Image Viewer</b> example shows how to combine "
                "QLabel and QScrollArea to display an image. QLabel is "
                "typically used for displaying text, but it can also display "
                "an image. QScrollArea provides a scrolling view around "
                "another widget. If the child widget exceeds the size of the "
                "frame, QScrollArea automatically provides scroll bars.</p>"
                "<p>The example demonstrates how QLabel's ability to scale "
                "its contents (QLabel.scaledContents), and QScrollArea's "
                "ability to automatically resize its contents "
                "(QScrollArea.widgetResizable), can be used to implement "
                "zooming and scaling features.</p>"
                "<p>In addition the example shows how to use QPainter to "
                "print an image.</p>")
                
    def createActions(self):
        self.openAct = QtWidgets.QAction("&Open...", self, shortcut="Ctrl+O",
                triggered=self.open)
        self.printAct = QtWidgets.QAction("&Print...", self, shortcut="Ctrl+P",
                enabled=False, triggered=self.printPreview)
        self.exitAct = QtWidgets.QAction("E&xit", self, shortcut="Ctrl+Q",
                triggered=self.close)
        self.zoomInAct = QtWidgets.QAction("Zoom &In (25%)", self,
                shortcut="Ctrl++", enabled=False, triggered=self.zoomIn)
        self.zoomOutAct = QtWidgets.QAction("Zoom &Out (25%)", self,
                shortcut="Ctrl+-", enabled=False, triggered=self.zoomOut)
        self.normalSizeAct = QtWidgets.QAction("&Normal Size", self,
                shortcut="Ctrl+S", enabled=False, triggered=self.normalSize)
        self.fitToWindowAct = QtWidgets.QAction("&Fit to Window", self,
                enabled=False, checkable=True, shortcut="Ctrl+F",
                triggered=self.fitToWindow)
        self.aboutAct = QtWidgets.QAction("&About", self, triggered=self.about)
        self.aboutQtAct = QtWidgets.QAction("About &Qt", self,
                triggered=QtWidgets.qApp.aboutQt)
                
    def createMenus(self):
        self.fileMenu = QtWidgets.QMenu("&File", self)
        self.fileMenu.addAction(self.openAct)
        self.fileMenu.addAction(self.printAct)
        self.fileMenu.addSeparator()
        self.fileMenu.addAction(self.exitAct)
        self.viewMenu = QtWidgets.QMenu("&View", self)
        self.viewMenu.addAction(self.zoomInAct)
        self.viewMenu.addAction(self.zoomOutAct)
        self.viewMenu.addAction(self.normalSizeAct)
        self.viewMenu.addSeparator()
        self.viewMenu.addAction(self.fitToWindowAct)
        self.helpMenu = QtWidgets.QMenu("&Help", self)
        self.helpMenu.addAction(self.aboutAct)
        self.helpMenu.addAction(self.aboutQtAct)
        self.menuBar().addMenu(self.fileMenu)
        self.menuBar().addMenu(self.viewMenu)
        self.menuBar().addMenu(self.helpMenu)
        
    def updateActions(self):
        self.zoomInAct.setEnabled(not self.fitToWindowAct.isChecked())
        self.zoomOutAct.setEnabled(not self.fitToWindowAct.isChecked())
        self.normalSizeAct.setEnabled(not self.fitToWindowAct.isChecked())
    
    def scaleImage(self, factor):
        self.scaleFactor *= factor
        self.imageLabel.resize(self.scaleFactor * self.imageLabel.pixmap().size())
        self.adjustScrollBar(self.scrollArea.horizontalScrollBar(), factor)
        self.adjustScrollBar(self.scrollArea.verticalScrollBar(), factor)
        self.zoomInAct.setEnabled(self.scaleFactor < 3.0)
        self.zoomOutAct.setEnabled(self.scaleFactor > 0.333)
    
    def adjustScrollBar(self, scrollBar, factor):
        scrollBar.setValue(int(factor * scrollBar.value()
                                + ((factor - 1) * scrollBar.pageStep()/2)))


if __name__ == '__main__':
    import sys
    app = QtWidgets.QApplication(sys.argv)
    imageViewer = ImageViewer()
    imageViewer.show()
    sys.exit(app.exec_())