构建基于 Node.js 的条形码识别程序 已翻译 100%

In this post, let’s take a glimpse of how easy to build a custom Node module on Windows, Linux, and Mac by wrapping Dynamsoft Barcode Reader SDK, as well as how to integrate the module to quickly implement an online barcode reader.

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More and more Web developers tend to choose Node.js to build their Website because it is convenient to build complex server-side Web applications using only JavaScript. To extend and empower the functionalities of Node.js applications on different platforms, Node.js allows developers to create addons in C/C++. In this post, let’s take a glimpse of how easy to build a custom Node module on Windows, Linux, and Mac by wrapping Dynamsoft Barcode Reader SDK, as well as how to integrate the module to quickly implement an online barcode reader.

• Download Node.js Barcode Demo - 526.1 KB

Introduction

Dynamsoft Barcode Reader provides C/C++ shared libraries for Windows, Linux, and Mac. The ultimate benefit is that any high-level programming languages, such as JavaScript, Python, Java, Ruby, PHP and so on, are capable of wrapping C/C++ APIs using an extension or an addon. No matter which programming language you are familiar with, the SDK will expedite the coding work of barcode reader app with a few lines of code.

Supported 1D/2D Barcode Types

• Code 39, Code 93, Code 128, Codabar, Interleaved 2 of 5, EAN-8, EAN-13, UPC-A, UPC-E,Industrial 2 of 5

• QRCode

• DataMatrix

• PDF417

Supported Image Types

• BMP, JPEG, PNG, GIF, TIFF, PDF

Environment

• Windows, Linux & Mac

• Node v5.5.0

Node.js Barcode Addon

Node.js Addons are dynamically-linked shared objects written in C/C++. If you have never touched this part before, you’d better follow the official tutorial to get started.

Create Addon

Create dbr.cc and add a method DecodeFile:

#include <node.h>
#include <string.h>
#include "If_DBR.h"
#include "BarcodeFormat.h"
#include "BarcodeStructs.h"
#include "ErrorCode.h"
 
using namespace v8;
 
void DecodeFile(const FunctionCallbackInfo<Value>& args) {
 
}
 
void Init(Handle<Object> exports) {
    NODE_SET_METHOD(exports, "decodeFile", DecodeFile);
}
 
NODE_MODULE(dbr, Init)

Parse parameters that passed from JavaScript:

Isolate* isolate = Isolate::GetCurrent();
HandleScope scope(isolate);
String::Utf8Value license(args[0]->ToString());
String::Utf8Value fileName(args[1]->ToString());
char *pFileName = *fileName;
char *pszLicense = *license;
__int64 llFormat = args[2]->IntegerValue();
Local<Function> cb = Local<Function>::Cast(args[3]);

Decode barcode image:

int iMaxCount = 0x7FFFFFFF;
ReaderOptions ro = {0};
pBarcodeResultArray pResults = NULL;
ro.llBarcodeFormat = llFormat;
ro.iMaxBarcodesNumPerPage = iMaxCount;
 
DBR_InitLicense(pszLicense);
// Decode barcode image
int ret = DBR_DecodeFile(pFileName, &ro, &pResults);

Convert barcode formats to String:

const char * GetFormatStr(__int64 format)
{
    if (format == CODE_39)
        return "CODE_39";
    if (format == CODE_128)
        return "CODE_128";
    if (format == CODE_93)
        return "CODE_93";
    if (format == CODABAR)
        return "CODABAR";
    if (format == ITF)
        return "ITF";
    if (format == UPC_A)
        return "UPC_A";
    if (format == UPC_E)
        return "UPC_E";
    if (format == EAN_13)
        return "EAN_13";
    if (format == EAN_8)
        return "EAN_8";
    if (format == INDUSTRIAL_25)
        return "INDUSTRIAL_25";
    if (format == QR_CODE)
        return "QR_CODE";
    if (format == PDF417)
        return "PDF417";
    if (format == DATAMATRIX)
        return "DATAMATRIX";
 
    return "UNKNOWN";
}

Convert results to v8 object:

Local<Array> barcodeResults = Array::New(isolate);
 
for (int i = 0; i < count; i++)
{
    tmp = ppBarcodes[i];
 
    Local<Object> result = Object::New(isolate);
    result->Set(String::NewFromUtf8(isolate, "format"), String::NewFromUtf8(isolate, GetFormatStr(tmp->llFormat)));
    result->Set(String::NewFromUtf8(isolate, "value"), String::NewFromUtf8(isolate, tmp->pBarcodeData));
 
    barcodeResults->Set(Number::New(isolate, i), result);
}

Build Addon

Prerequisites:

• Windows: Install DBR for Windows, Visual Studio, and Python v2.7.

• Linux: Install DBR for Linux.

• Mac: Install DBR for Mac and Xcode.

Install node-gyp:

npm install -g node-gyp

Create binding.gyp for multiplatform compilation:

{
  "targets": [
    {
      'target_name': "dbr",
      'sources': [ "dbr.cc" ],
      'conditions': [
          ['OS=="linux"', {
            'defines': [
              'LINUX_DBR',
            ],
            'include_dirs': [
                "/home/xiao/Dynamsoft/BarcodeReader4.0/Include"
            ],
            'libraries': [
                "-lDynamsoftBarcodeReaderx64", "-L/home/xiao/Dynamsoft/BarcodeReader4.0/Redist"
            ],
            'copies': [
            {
              'destination': 'build/Release/',
              'files': [
                '/home/xiao/Dynamsoft/BarcodeReader4.0/Redist/libDynamsoftBarcodeReaderx64.so'
              ]
            }]
          }],
          ['OS=="win"', {
            'defines': [
              'WINDOWS_DBR',
            ],
            'include_dirs': [
                "F:\Program Files (x86)\Dynamsoft\Barcode Reader 4.1\Components\C_C++\Include"
            ],
            'libraries': [
                "-lF:\Program Files (x86)\Dynamsoft\Barcode Reader 4.1\Components\C_C++\Lib\DBRx64.lib"
            ],
            'copies': [
            {
              'destination': 'build/Release/',
              'files': [
                'F:\Program Files (x86)\Dynamsoft\Barcode Reader 4.1\Components\C_C++\Redist\DynamsoftBarcodeReaderx64.dll'
              ]
            }]
          }],
          ['OS=="mac"', {
            'defines': [
              'MAC_DBR',
            ],
            'include_dirs' : [
                "/Applications/Dynamsoft/Barcode\ Reader\ 4.1/Include"
            ],
            'libraries': [
                "-lDynamsoftBarcodeReader"
            ]
          }]
      ]
    }
  ]
}

Replace the DBR Installation Directory with yours.

Configure the building environment:

node-gyp configure

Probably you will see the following error when configuring the environment on Mac:

error: xcode-select: error: tool 'xcodebuild' requires Xcode, but active developer directory '/Library/Developer/CommandLineTools' is a command line tools instance

Here is the solution:

sudo xcode-select --switch /Applications/Xcode.app/Contents/Developer

Build the project:

node-gyp build

Online Barcode Reader

You have successfully built the Node barcode reader module. Now it is time to create a simple barcode reader app.

Install Express and Formidable:

npm install express
npm install formidable

Create a simple Website using Express:

var formidable = require('formidable');
var util = require('util');
var express = require('express');
var fs = require('fs');
var app = express();
var path = require('path');
var dbr = require('./build/Release/dbr');
var http = require('http');
 
fs.readFile('./license.txt', 'utf8', function(err, data) {
 
  app.use(express.static(__dirname));
  app.use(function(req, res, next) {
    res.header("Access-Control-Allow-Origin", "*");
    res.header("Access-Control-Allow-Methods", "PUT, POST, GET, DELETE, OPTIONS");
    res.header("Access-Control-Allow-Headers", "X-Requested-With, content-type");
    res.header("Access-Control-Allow-Credentials", true);
    next();
  });
 
  var server = app.listen(2016, function() {
    var host = server.address().address;
    var port = server.address().port;
    console.log('listening at http://%s:%s', host, port);
  });
});

Use Formidable to extract the image data from Form.

app.post('/upload', function(req, res) {
    var form = new formidable.IncomingForm();
    form.parse(req, function(err, fields, files) {
      var dir = 'uploads';
 
      fs.mkdir(dir, function(err) {
        var flag = fields.uploadFlag;
        var barcodeType = parseInt(fields.barcodetype);
 
        console.log('flag: ' + flag);
 
        if (flag === '1') { // read barcode image file
          fs.readFile(files.fileToUpload.path, function(err, data) {
            // save file from temp dir to new dir
            var fileName = path.join(__dirname, dir, files.fileToUpload.name);
            console.log(fileName);
            fs.writeFile(fileName, data, function(err) {
              if (err) throw err;
 
            });
          });
 
        } else { // read barcode image url
          var tmpFileName = path.join(__dirname, dir, 'tmp.jpg');
          var tmp = fs.createWriteStream(tmpFileName);
          var url = fields.fileToDownload;
          console.log('url: ' + url);
          http.get(url, function(response) {
            response.pipe(tmp);
            tmp.on('finish', function() {
              tmp.close(function() {
 
              });
            });
          });
        }
      });
 
    });
  });

Import the barcode module to decode the image file.

decodeBarcode(res, license, tmpFileName, barcodeType);

Run the app:

node server.js

Visit http://localhost:2016/index.htm:

Do you want to build a barcode reader app on Windows, Linux or Mac? Download the sample code and get your hands dirty now. For more information about Dynamsoft Barcode Reader, please contact support@dynamsoft.com.