Building Python Barcode Extension with DBR 5.2 for Linux

According to the statistics of Stack Overflow traffic, Python is the fastest-growing major programming language in high-income countries. Python seems to be promising in the future. I have noticed that many of the developers who would like to use Dynamsoft Barcode Reader SDK for Linux are more interested in Python rather than C/C++ or Java. In this post, I will illustrate how to build the Python barcode extension with DBR 5.2.

Writing Python Barcode Extension in C/C++

Dynamsoft Barcode Reader 5.2 for Linux provides C/C++ APIs, which means you need to create a Python wrapper yourself.

Setting Up Environment

The Ubuntu subsystem is my first choice for developing Linux app on Windows 10.

Download Numpy 1.11.2.

Extract and install Numpy

cd numpy-1.11.2 sudo python setup.py build install

Find the path of ndarraytypes.h:

sudo find /usr -name ndarraytypes.h

Create setup.py and add the header file directory:

from distutils.core import setup, Extension
module_dbr = Extension('dbr',
sources = ['dbr.c'],
include_dirs=["/usr/local/lib/python2.7/dist-packages/numpy-1.11.2-py2.7-linux-x86_64.egg/numpy/core/include/numpy/"],
libraries=['DynamsoftBarcodeReader'])
setup (name = 'DynamsoftBarcodeReader',
version = '1.0',
description = 'Python barcode extension',
ext_modules = [module_dbr])

Extract dbr_linux_5.2.tar.gz:

tar -xvf dbr_linux_5.2.tar.gz

Create a symlink for libDynamsoftBarcodeReaderx64.so:

sudo ln -s <Your PATH>/libDynamsoftBarcodeReaderx64.so /usr/lib/libDynamsoftBarcodeReader.so

The bridging C/C++ code

Include header files:

#include <Python.h>
#include "DynamsoftBarcodeReader.h"
#include <ndarraytypes.h>

Define methods and initialize Python module:

static PyMethodDef Methods[] =
{
{"create", create, METH_VARARGS, NULL},
{"destroy", destroy, METH_VARARGS, NULL},
{"initLicense", initLicense, METH_VARARGS, NULL},
{"decodeFile", decodeFile, METH_VARARGS, NULL},
{"decodeBuffer", decodeBuffer, METH_VARARGS, NULL},
{NULL, NULL, 0, NULL}
};
PyMODINIT_FUNC
initdbr(void)
{
(void) Py_InitModule("dbr", Methods);
}

Initialize DBR license:

static PyObject *
initLicense(PyObject *self, PyObject *args)
{
if (!createDBR())
{
return NULL;
}
char *pszLicense;
if (!PyArg_ParseTuple(args, "s", &pszLicense)) {
return NULL;
}
int ret = DBR_InitLicenseEx(hBarcode, pszLicense);
return Py_BuildValue("i", ret);
}

Pass a file name and read barcodes:

/**
* Decode barcode from a file
*/
static PyObject *
decodeFile(PyObject *self, PyObject *args)
{
if (!createDBR())
{
return NULL;
}
char *pFileName;
int iFormat;
if (!PyArg_ParseTuple(args, "si", &pFileName, &iFormat)) {
return NULL;
}
// Initialize Dynamsoft Barcode Reader
int iMaxCount = 0x7FFFFFFF;
SBarcodeResultArray *pResults = NULL;
DBR_SetBarcodeFormats(hBarcode, iFormat);
DBR_SetMaxBarcodesNumPerPage(hBarcode, iMaxCount);
// Barcode detection
int ret = DBR_DecodeFileEx(hBarcode, pFileName, &pResults);
// Wrap results
PyObject *list = createPyResults(pResults);
return list;
}

Give an image buffer and read barcodes:

/**
* Decode barcode from an image buffer.
*/
static PyObject *
decodeBuffer(PyObject *self, PyObject *args)
{
if (!createDBR())
{
return NULL;
}
PyObject *o;
int iFormat;
if (!PyArg_ParseTuple(args, "Oi", &o, &iFormat))
return NULL;
PyObject *ao = PyObject_GetAttrString(o, "__array_struct__");
if ((ao == NULL) || !PyCObject_Check(ao)) {
PyErr_SetString(PyExc_TypeError, "object does not have array interface");
return NULL;
}
PyArrayInterface *pai = (PyArrayInterface*)PyCObject_AsVoidPtr(ao);
if (pai->two != 2) {
PyErr_SetString(PyExc_TypeError, "object does not have array interface");
Py_DECREF(ao);
return NULL;
}
// Get image information
char *buffer = (char*)pai->data; // The address of image data
int width = pai->shape[1];       // image width
int height = pai->shape[0];      // image height
int size = pai->strides[0] * pai->shape[0]; // image size = stride * height
// Initialize Dynamsoft Barcode Reader
int iMaxCount = 0x7FFFFFFF;
SBarcodeResultArray *pResults = NULL;
DBR_SetBarcodeFormats(hBarcode, iFormat);
DBR_SetMaxBarcodesNumPerPage(hBarcode, iMaxCount);
// Detect barcodes
int iRet = DBR_DecodeBufferEx(hBarcode, buffer, width, height, width * 3, IPF_RGB_888, &pResults);
// Wrap results
PyObject *list = createPyResults(pResults);
Py_DECREF(ao);
return list;
}

Convert results to Python Object:

static PyObject *createPyResults(SBarcodeResultArray *pResults)
{
// Get barcode results
int count = pResults->iBarcodeCount;
SBarcodeResult** ppBarcodes = pResults->ppBarcodes;
SBarcodeResult* tmp = NULL;
// Create a Python object to store results
PyObject* list = PyList_New(count);
PyObject* result = NULL;
for (int i = 0; i < count; i++)
{
tmp = ppBarcodes[i];
result = PyString_FromString(tmp->pBarcodeData);
PyList_SetItem(list, i, Py_BuildValue("sN", GetFormatStr(tmp->emBarcodeFormat), result)); // Add results to list
}
// Release memory
DBR_FreeBarcodeResults(&pResults);
return list;
}

Build and install the Python barcode extension:

sudo python setup.py build install

A command line barcode app

Read barcodes from a picture file:

import os.path
import dbr
def initLicense(license):
dbr.initLicense(license)
def decodeFile(fileName):
dbr.initLicense("t0068MgAAAGvV3VqfqOzkuVGi7x/PFfZUQoUyJOakuduaSEoI2Pc8+kMwjrojxQgE5aJphmhagRmq/S9lppTkM4w3qCQezxk=")
formats = 0x3FF | 0x2000000 | 0x8000000 | 0x4000000; # 1D, QRCODE, PDF417, DataMatrix
results = dbr.decodeFile(fileName, formats)
for result in results:
print("barcode format: " + result[0])
print("barcode value: " + result[1])
if __name__ == "__main__":
barcode_image = input("Enter the barcode file: ");
if not os.path.isfile(barcode_image):
print "It is not a valid file."
else:
decodeFile(barcode_image);

Run the app:

python test.py

Reference

• Python/C API Reference Manual

Source Code

https://github.com/dynamsoft-dbr/linux-barcode-sdk-python-wrapper

Originally published at www.codepool.biz on September 18, 2017.