#!/usr/bin/env python
 
 
#############################################################################
##
## Copyright (C) 2013 Riverbank Computing Limited.
## Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).
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## This file is part of the examples of PyQt.
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##     the documentation and/or other materials provided with the
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from PyQt5.QtCore import QDir, Qt
from PyQt5.QtGui import QImage, QPainter, QPalette, QPixmap
from PyQt5.QtWidgets import (QAction, QApplication, QFileDialog, QLabel,
        QMainWindow, QMenu, QMessageBox, QScrollArea, QSizePolicy)
from PyQt5.QtPrintSupport import QPrintDialog, QPrinter
 
 
class ImageViewer(QMainWindow):
    def __init__(self):
        super(ImageViewer, self).__init__()
 
        self.printer = QPrinter()
        self.scaleFactor = 0.0
 
        self.imageLabel = QLabel()
        self.imageLabel.setBackgroundRole(QPalette.Base)
        self.imageLabel.setSizePolicy(QSizePolicy.Ignored, QSizePolicy.Ignored)
        self.imageLabel.setScaledContents(True)
 
        self.scrollArea = QScrollArea()
        self.scrollArea.setBackgroundRole(QPalette.Dark)
        self.scrollArea.setWidget(self.imageLabel)
        self.setCentralWidget(self.scrollArea)
 
        self.createActions()
        self.createMenus()
 
        self.setWindowTitle("Image Viewer")
        self.resize(500, 400)
 
    def open(self):
        fileName, _ = QFileDialog.getOpenFileName(self, "Open File",
                QDir.currentPath())
        if fileName:
            image = QImage(fileName)
            if image.isNull():
                QMessageBox.information(self, "Image Viewer",
                        "Cannot load %s." % fileName)
                return
 
            self.imageLabel.setPixmap(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 print_(self):
        dialog = QPrintDialog(self.printer, self)
        if dialog.exec_():
            painter = QPainter(self.printer)
            rect = painter.viewport()
            size = self.imageLabel.pixmap().size()
            size.scale(rect.size(), Qt.KeepAspectRatio)
            painter.setViewport(rect.x(), rect.y(), size.width(), size.height())
            painter.setWindow(self.imageLabel.pixmap().rect())
            painter.drawPixmap(0, 0, self.imageLabel.pixmap())
 
    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):
        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 = QAction("&Open...", self, shortcut="Ctrl+O",
                triggered=self.open)
 
        self.printAct = QAction("&Print...", self, shortcut="Ctrl+P",
                enabled=False, triggered=self.print_)
 
        self.exitAct = QAction("E&xit", self, shortcut="Ctrl+Q",
                triggered=self.close)
 
        self.zoomInAct = QAction("Zoom &In (25%)", self, shortcut="Ctrl++",
                enabled=False, triggered=self.zoomIn)
 
        self.zoomOutAct = QAction("Zoom &Out (25%)", self, shortcut="Ctrl+-",
                enabled=False, triggered=self.zoomOut)
 
        self.normalSizeAct = QAction("&Normal Size", self, shortcut="Ctrl+S",
                enabled=False, triggered=self.normalSize)
 
        self.fitToWindowAct = QAction("&Fit to Window", self, enabled=False,
                checkable=True, shortcut="Ctrl+F", triggered=self.fitToWindow)
 
        self.aboutAct = QAction("&About", self, triggered=self.about)
 
        self.aboutQtAct = QAction("About &Qt", self,
                triggered=QApplication.instance().aboutQt)
 
    def createMenus(self):
        self.fileMenu = QMenu("&File", self)
        self.fileMenu.addAction(self.openAct)
        self.fileMenu.addAction(self.printAct)
        self.fileMenu.addSeparator()
        self.fileMenu.addAction(self.exitAct)
 
        self.viewMenu = 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 = 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 = QApplication(sys.argv)
    imageViewer = ImageViewer()
    imageViewer.show()
    sys.exit(app.exec_())