在 PyQt5 中打印 pdf 文档

Question

我想将pdf 文档打印到打印机。到目前为止，我有这个代码。

def printDialog(self):
        filePath, filter = QFileDialog.getOpenFileName(self, 'Open file', '', 'Text (*.txt);;PDF (*.pdf)')
        if not filePath:
          return
        file_extension = os.path.splitext(filePath)[1]
        if file_extension == ".txt":
            doc = QtGui.QTextDocument()
            try:
                with open(filePath, 'r') as txtFile:
                    doc.setPlainText(txtFile.read())
                printer = QPrinter(QPrinter.HighResolution)
                if not QPrintDialog(printer, self).exec_():
                    return
                doc.print_(printer)
            except Exception as e:
                print('Error trying to print: {}'.format(e))
        elif file_extension == ".pdf":
            printer = QPrintDialog(QPrinter.HighResolution)
            printer.setOutputFormat(QPrinter.PdfFormat)
            printer.setOutputFileName(filePath)
            # TODO
        else:
            pass

我不知道如何继续TODO 部分。

Answer 1

一种可能性是使用 pdf2image

一个 python (3.5+) 模块，包装 pdftoppm 和 pdftocairo 以将 PDF 转换为 PIL Image 对象

见https://pypi.org/project/pdf2image/

在上面的链接下，您将找到 poppler 的安装说明，它是模块的依赖项。

步骤

• PDF 文件已读取
• 借助pdf2image转换成图片
• 每个图像都是使用 QPaint 绘制的

代码的简单版本如下所示：

images = convert_from_path(filePath, dpi=300, output_folder=path)
painter = QPainter()
painter.begin(printer)
for i, image in enumerate(images):
    if i > 0:
        printer.newPage()
    rect = painter.viewport()
    qtImage = ImageQt(image)
    qtImageScaled = qtImage.scaled(rect.size(), Qt.KeepAspectRatio, Qt.SmoothTransformation)
    painter.drawImage(rect, qtImageScaled)
painter.end()

convert_from_path 的第二个参数描述了以 dpi 为单位的输出分辨率。设备坐标系中的目标矩形可以通过调用 QPainter 实例上的 viewport 来确定。最后，可以使用双线性滤波器算法将图像平滑地缩放到目标矩形。

独立的示例程序

我稍微修改了您的代码并创建了一个完全独立的示例。

不处理诸如纸张大小、分辨率、内存要求优化和错误处理等主题。目的是举一个最小的例子。

import os
import sys

from PIL.ImageQt import ImageQt
from PyQt5 import QtWidgets
from PyQt5.QtCore import QSize, Qt
from PyQt5.QtGui import QPainter
from PyQt5.QtPrintSupport import QPrintDialog, QPrinter
from PyQt5.QtWidgets import QMainWindow, QFileDialog, QPushButton
import tempfile

from pdf2image import convert_from_path


class PrintDemo(QMainWindow):

    def __init__(self):
        QMainWindow.__init__(self)

        self.setMinimumSize(QSize(192, 128))
        self.setWindowTitle("Print Demo")

        printButton = QPushButton('Print', self)
        printButton.clicked.connect(self.onPrint)
        printButton.resize(128, 32)
        printButton.move(32, 48)

    def onPrint(self):
        self.printDialog()

    def printDialog(self):
        filePath, filter = QFileDialog.getOpenFileName(self, 'Open file', '', 'PDF (*.pdf)')
        if not filePath:
            return
        file_extension = os.path.splitext(filePath)[1]

        if file_extension == ".pdf":
            printer = QPrinter(QPrinter.HighResolution)
            dialog = QPrintDialog(printer, self)
            if dialog.exec_() == QPrintDialog.Accepted:
                with tempfile.TemporaryDirectory() as path:
                    images = convert_from_path(filePath, dpi=300, output_folder=path)
                    painter = QPainter()
                    painter.begin(printer)
                    for i, image in enumerate(images):
                        if i > 0:
                            printer.newPage()
                        rect = painter.viewport()
                        qtImage = ImageQt(image)
                        qtImageScaled = qtImage.scaled(rect.size(), Qt.KeepAspectRatio, Qt.SmoothTransformation)
                        painter.drawImage(rect, qtImageScaled)
                    painter.end()
        else:
            pass


if __name__ == "__main__":
    app = QtWidgets.QApplication(sys.argv)
    mainWin = PrintDemo()
    mainWin.show()
    sys.exit(app.exec_())