如何用Qt Python创建简单的桌面条形码应用

水深无声 2022-01-14 18:05 252阅读 0赞

[2019独角兽企业重金招聘Python工程师标准>>> ][2019_Python_] ![hot3.png][]

Qt for Python可以快速跨平台的GUI应用。这篇文章分享下如何结合Dynamsoft Barcode Reader SDK来创建一个简单的读码应用。

## 安装Qt for Python ##

官方站点可以下载对应的[wheel文件][wheel]，或者通过命令行安装：

pip install pyside2

我之前用Python 3.6无法成功加载Qt：

Error:
    Traceback (most recent call last):
    File "test2.py", line 3, in <module>
    from PySide2.QtWidgets import (QApplication, QLabel, QPushButton, QVBoxLayout, QWidget)
    ImportError: DLL load failed: The specified procedure could not be found.

换成Python 3.7之后就好了。

## 安装Dynamsoft Barcode Reader ##

*  下载[barcode sdk][]。
 *  申请一个[免费试用的license][license]。
 *  获取[extension源码][extension]，然后编译安装：
    
        python setup.py build install

## 简单的Windows桌面扫码应用 ##

Qt安装之后可以用Qt designer来设计界面并生成Python代码。

运行`Python37\Lib\site-packages\PySide2\designer.exe`。

![qt-designer.PNG][]

设计好界面之后保存到.ui文件。

用`Python37\Scripts\pyside2-uic.exe`把.ui文件转换成Python文件:

pyside2-uic -x *.ui -o ui.py

之后可以直接运行这个Python文件。

应用界面很简单。Button用于加载图片，Label用于显示图片，Text用于显示结果。

import sys
    from PySide2.QtGui import QPixmap
     
    from PySide2.QtWidgets import QApplication, QLabel, QPushButton, QVBoxLayout, QWidget, QFileDialog, QTextEdit, QSizePolicy
    from PySide2.QtCore import Slot, Qt, QStringListModel, QSize
     
    import dbr
    import os
     
    class UI_Window(QWidget):
     
        def __init__(self):
            QWidget.__init__(self)
     
            # The default barcode image.
            dir_path = os.path.dirname(os.path.realpath(__file__))
            filename = os.path.join(dir_path, 'image.tif')
     
            # Create a layout.
            layout = QVBoxLayout()
     
            # Add a button
            self.btn = QPushButton("Load an image")
            self.btn.clicked.connect(self.pickFile)
            layout.addWidget(self.btn)
     
            # Add a label
            self.label = QLabel()
            self.label.setFixedSize(640, 640)
            pixmap = self.resizeImage(filename)
            self.label.setPixmap(pixmap)
            layout.addWidget(self.label)
     
            # Add a text area
            self.results = QTextEdit()
            self.readBarcode(filename)
            layout.addWidget(self.results)
     
            # Set the layout
            self.setLayout(layout)
            self.setWindowTitle("Dynamsoft Barcode Reader")
            self.setFixedSize(800, 800)

点击按钮之后调用系统对话框来加载文件：

def pickFile(self):
            # Load an image file.
            filename = QFileDialog.getOpenFileName(self, 'Open file',
                                                   'E:\\Program Files (x86)\\Dynamsoft\\Barcode Reader 6.4.1\\Images', "Barcode images (*)")
            # Show barcode images
            pixmap = self.resizeImage(filename[0])
            self.label.setPixmap(pixmap)
     
            # Read barcodes
            self.readBarcode(filename[0])

调节图片尺寸，让图片显示在固定区域内：

def resizeImage(self, filename):
            pixmap = QPixmap(filename)
            lwidth = self.label.maximumWidth()
            pwidth = pixmap.width()
            lheight = self.label.maximumHeight()
            pheight = pixmap.height()
     
            wratio = pwidth * 1.0 / lwidth
            hratio = pheight * 1.0 / lheight
     
            if pwidth > lwidth or pheight > lheight:
                if wratio > hratio:
                    lheight = pheight / wratio
                else:
                    lwidth = pwidth / hratio
     
                scaled_pixmap = pixmap.scaled(lwidth, lheight)
                return scaled_pixmap
            else:
                return pixmap

调用barcode接口识别条形码：

def readBarcode(self, filename):
            dbr.initLicense("<Your License>")
            results = dbr.decodeFile(filename, 0x3FF | 0x2000000 | 0x4000000 | 0x8000000 | 0x10000000)
     
            out = ''
            index = 0
            for result in results:
                out += "Index: " + str(index) + "\n"
                out += "Barcode format: " + result[0] + '\n'
                out += "Barcode value: " + result[1] + '\n'
                out += '-----------------------------------\n'
                index += 1
     
            self.results.setText(out)

运行程序：

python barcode-reader.py

![qt-python-barcode-reader.PNG][]

## 源码 ##

[https://github.com/dynamsoft-dbr/python/tree/master/examples/qt][https_github.com_dynamsoft-dbr_python_tree_master_examples_qt]

转载于:https://my.oschina.net/yushulx/blog/3005807

[2019_Python_]: https://my.oschina.net/u/2663968/blog/3061697
[hot3.png]: /images/20220114/7be29491728f4cbd963c06066558c752.png
[wheel]: http://download.qt.io/official_releases/QtForPython/pyside2/
[barcode sdk]: https://www.dynamsoft.com/Downloads/Dynamic-Barcode-Reader-Download.aspx
[license]: https://www.dynamsoft.com/CustomerPortal/Portal/Triallicense.aspx
[extension]: https://github.com/dynamsoft-dbr/python
[qt-designer.PNG]: /images/20220114/96b118a1a19b4d6c94a2cf2682e6617d.png
[qt-python-barcode-reader.PNG]: /images/20220114/96e0105f51dd474390ecc0e0bfdcac88.png
[https_github.com_dynamsoft-dbr_python_tree_master_examples_qt]: https://github.com/dynamsoft-dbr/python/tree/master/examples/qt