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Add a ctypes example
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‎examples/ctypes/.gitignore

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/analytics-quickstart
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/node_modules
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build

‎examples/ctypes/README.md

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# Python Ctypes for Dynamsoft Barcode Shared Library
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This repository demonstrates how to load and utilize Dynamsoft Barcode Reader shared libraries using Python's Ctypes module.
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## Why Use Ctypes?
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While Dynamsoft Barcode Reader for Python is available on [PyPI](https://pypi.org/project/dbr/) and can be installed with:
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```bash
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pip install dbr
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```
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This project explores an alternative approach to invoking C APIs from shared libraries using Ctypes, offering a way to use C/C++ native threads and callbacks in Python.
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## How to Use
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1. Build the `bridge` CMake project:
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**On Windows**:
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```bash
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cd bridge && mkdir build && cd build
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cmake -DCMAKE_GENERATOR_PLATFORM=x64 ..
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cmake --build .
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```
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**On Linux:**
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```bash
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cd bridge && mkdir build && cd build
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cmake ..
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cmake --build .
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```
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2. Get a valid license key from [Dynamsoft](https://www.dynamsoft.com/customer/license/trialLicense?product=dbr). Then, update the license key in the `success.py` file.
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```python
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license_key = b"LICENSE-KEY"
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```
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3. Execute the `success.py` script.
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```bash
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python success.py
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```
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## Blog
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[Python Ctypes for Loading and Calling Shared Libraries](https://www.dynamsoft.com/codepool/python-ctypes-load-call-shared-library.html)

‎examples/ctypes/bridge/CMakeLists.txt

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cmake_minimum_required(VERSION 3.0.0)
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project(bridge VERSION 0.1.0)
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INCLUDE_DIRECTORIES("${CMAKE_CURRENT_SOURCE_DIR}" "${CMAKE_CURRENT_SOURCE_DIR}/../../../include")
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if (CMAKE_HOST_WIN32)
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LINK_DIRECTORIES("${CMAKE_CURRENT_SOURCE_DIR}/../../../lib/Win")
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else()
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LINK_DIRECTORIES("${CMAKE_CURRENT_SOURCE_DIR}/../../../lib/linux")
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endif()
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add_library(${PROJECT_NAME} SHARED bridge.cpp)
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if(CMAKE_HOST_WIN32)
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target_link_libraries (${PROJECT_NAME} "DBRx64")
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else()
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target_link_libraries (${PROJECT_NAME} "DynamsoftBarcodeReader")
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endif()

‎examples/ctypes/bridge/bridge.cpp

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#include <stdio.h>
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#include <string.h>
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#include <stdlib.h>
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#include "bridge.h"
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#include <thread>
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using namespace std;
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callback_t callback = NULL;
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thread t;
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ResultList *dbr_get_results(void *barcodeReader)
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{
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TextResultArray *pResults;
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int ret = DBR_GetAllTextResults(barcodeReader, &pResults);
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int count = pResults->resultsCount;
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TextResult **results = pResults->results;
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ResultInfo **pResultInfo = (ResultInfo **)malloc(sizeof(ResultInfo *) * count);
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ResultList *resultList = (ResultList *)malloc(sizeof(ResultList));
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resultList->size = count;
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resultList->pResultInfo = pResultInfo;
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for (int i = 0; i < count; i++)
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{
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TextResult *pResult = results[i];
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ResultInfo *pInfo = (ResultInfo *)malloc(sizeof(ResultInfo));
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pInfo->format = NULL;
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pInfo->text = NULL;
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pResultInfo[i] = pInfo;
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// printf("Barcode format: %s, text: %s\n", pResult->barcodeFormatString, pResult->barcodeText);
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pInfo->format = (char *)calloc(strlen(pResult->barcodeFormatString) + 1, sizeof(char));
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strncpy(pInfo->format, pResult->barcodeFormatString, strlen(pResult->barcodeFormatString));
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pInfo->text = (char *)calloc(strlen(pResult->barcodeText) + 1, sizeof(char));
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strncpy(pInfo->text, pResult->barcodeText, strlen(pResult->barcodeText));
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}
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DBR_FreeTextResults(&pResults);
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return resultList;
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}
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void dbr_free_results(ResultList *resultList)
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{
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int count = resultList->size;
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ResultInfo **pResultInfo = resultList->pResultInfo;
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for (int i = 0; i < count; i++)
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{
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ResultInfo *resultList = pResultInfo[i];
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if (resultList)
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{
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if (resultList->format != NULL)
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free(resultList->format);
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if (resultList->text != NULL)
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free(resultList->text);
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free(resultList);
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}
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}
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if (pResultInfo != NULL)
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free(pResultInfo);
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}
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void thread_func(void *barcodeReader, const char *fileName)
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{
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DBR_DecodeFile(barcodeReader, fileName, "");
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TextResultArray *pResults;
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int ret = DBR_GetAllTextResults(barcodeReader, &pResults);
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int count = pResults->resultsCount;
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TextResult **results = pResults->results;
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ResultInfo **pResultInfo = (ResultInfo **)malloc(sizeof(ResultInfo *) * count);
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ResultList *resultList = (ResultList *)malloc(sizeof(ResultList));
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resultList->size = count;
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resultList->pResultInfo = pResultInfo;
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for (int i = 0; i < count; i++)
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{
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TextResult *pResult = results[i];
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ResultInfo *pInfo = (ResultInfo *)malloc(sizeof(ResultInfo));
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pInfo->format = NULL;
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pInfo->text = NULL;
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pResultInfo[i] = pInfo;
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// printf("Barcode format: %s, text: %s\n", pResult->barcodeFormatString, pResult->barcodeText);
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pInfo->format = (char *)calloc(strlen(pResult->barcodeFormatString) + 1, sizeof(char));
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strncpy(pInfo->format, pResult->barcodeFormatString, strlen(pResult->barcodeFormatString));
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pInfo->text = (char *)calloc(strlen(pResult->barcodeText) + 1, sizeof(char));
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strncpy(pInfo->text, pResult->barcodeText, strlen(pResult->barcodeText));
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}
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DBR_FreeTextResults(&pResults);
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if (callback)
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{
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int res = callback(resultList);
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}
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}
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void thread_decode(void *barcodeReader, const char *fileName)
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{
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t = thread(thread_func, barcodeReader, fileName);
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t.join();
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}
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int registerCallback(callback_t foo)
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{
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callback = foo;
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return 0;
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}

‎examples/ctypes/bridge/bridge.h

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# include "DynamsoftBarcodeReader.h"
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#if !defined(_WIN32) && !defined(_WIN64)
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#define EXPORT_API
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#else
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#define EXPORT_API __declspec(dllexport)
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#endif
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typedef struct {
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char* format;
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char* text;
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} ResultInfo;
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typedef struct {
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int size;
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ResultInfo** pResultInfo;
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} ResultList;
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typedef int (*callback_t)(ResultList*);
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#ifdef __cplusplus
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extern "C" {
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#endif
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EXPORT_API ResultList* dbr_get_results(void* barcodeReader);
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EXPORT_API void dbr_free_results(ResultList* resultList);
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EXPORT_API void thread_decode(void* barcodeReader, const char *fileName);
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EXPORT_API int registerCallback(callback_t foo);
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#ifdef __cplusplus
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}
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#endif

‎examples/ctypes/failure.py

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import os
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import platform
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from ctypes import *
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system = platform.system()
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class SamplingImageData(Structure):
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_fields_ = [
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("bytes", POINTER(c_ubyte)),
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("width", c_int),
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("height", c_int)
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]
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class LocalizationResult(Structure):
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_fields_ = [
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("terminatePhase", c_int),
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("barcodeFormat", c_int),
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("barcodeFormatString", c_char_p),
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("barcodeFormat_2", c_int),
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("barcodeFormatString_2", c_char_p),
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("x1", c_int),
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("y1", c_int),
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("x2", c_int),
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("y2", c_int),
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("x3", c_int),
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("y3", c_int),
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("x4", c_int),
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("y4", c_int),
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("angle", c_int),
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("moduleSize", c_int),
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("pageNumber", c_int),
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("regionName", c_char_p),
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("documentName", c_char_p),
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("resultCoordinateType", c_int),
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("accompanyingTextBytes", c_char_p),
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("accompanyingTextBytesLength", c_int),
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("confidence", c_int),
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("transformationMatrix", c_double * 9),
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("reserved", c_char * 52)
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]
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class ExtendedResult(Structure):
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_fields_ = [
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("resultType", c_int),
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("barcodeFormat", c_int),
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("barcodeFormatString", c_char_p),
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("barcodeFormat_2", c_int),
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("barcodeFormatString_2", c_char_p),
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("confidence", c_int),
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("bytes", POINTER(c_ubyte)),
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("bytesLength", c_int),
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("accompanyingTextBytes", POINTER(c_ubyte)),
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("accompanyingTextBytesLength", c_int),
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("deformation", c_int),
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("detailedResult", c_void_p),
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("samplingImage", SamplingImageData),
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("clarity", c_int),
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("reserved", c_char * 40)
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]
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class TextResult(Structure):
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_fields_ = [
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("barcodeFormat", c_int),
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("barcodeFormatString", c_char_p),
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("barcodeFormat_2", c_int),
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("barcodeFormatString_2", c_char_p),
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("barcodeText", c_char_p),
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("barcodeBytes", POINTER(c_ubyte)),
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("barcodeBytesLength", c_int),
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("localizationResult", POINTER(LocalizationResult)),
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("detailedResult", c_void_p),
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("resultsCount", c_int),
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("results", POINTER(POINTER(ExtendedResult))),
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("exception", c_char_p),
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("isDPM", c_int),
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("isMirrored", c_int),
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("reserved", c_char * 44)
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]
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class TextResultArray(Structure):
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_fields_ = [
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("resultsCount", c_int),
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("results", POINTER(POINTER(TextResult)))
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]
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dbr = None
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if 'Windows' in system:
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dll_path = license_dll_path = os.path.join(os.path.abspath(
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'.'), r'..\..\lib\win\DynamsoftBarcodeReaderx64.dll')
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# os.environ['path'] += ';' + dll_path
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# print(os.environ['path'])
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dbr = windll.LoadLibrary(dll_path)
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else:
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dbr = CDLL(os.path.join(os.path.abspath('.'),
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'../../lib/linux/libDynamsoftBarcodeReader.so'))
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# DBR_InitLicense
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DBR_InitLicense = dbr.DBR_InitLicense
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DBR_InitLicense.argtypes = [c_char_p, c_char_p, c_int]
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DBR_InitLicense.restype = c_int
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license_key = b"DLS2eyJoYW5kc2hha2VDb2RlIjoiMjAwMDAxLTE2NDk4Mjk3OTI2MzUiLCJvcmdhbml6YXRpb25JRCI6IjIwMDAwMSIsInNlc3Npb25QYXNzd29yZCI6IndTcGR6Vm05WDJrcEQ5YUoifQ=="
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error_msg_buffer = create_string_buffer(256)
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error_msg_buffer_len = len(error_msg_buffer)
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# https://www.dynamsoft.com/customer/license/trialLicense?product=dbr
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ret = DBR_InitLicense(license_key, error_msg_buffer, error_msg_buffer_len)
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print('initLicense: {}'.format(ret))
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# DBR_CreateInstance
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DBR_CreateInstance = dbr.DBR_CreateInstance
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DBR_CreateInstance.restype = c_void_p
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instance = dbr.DBR_CreateInstance()
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# DBR_DecodeFile
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DBR_DecodeFile = dbr.DBR_DecodeFile
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DBR_DecodeFile.argtypes = [c_void_p, c_char_p, c_char_p]
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DBR_DecodeFile.restype = c_int
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ret = DBR_DecodeFile(instance, c_char_p(
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'test.png'.encode('utf-8')), c_char_p(''.encode('utf-8')))
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print('DBR_DecodeFile: {}'.format(ret))
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####################################################################################
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# Failed to get barcode detection results
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# DBR_GetAllTextResults
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pResults = POINTER(TextResultArray)()
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DBR_GetAllTextResults = dbr.DBR_GetAllTextResults
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DBR_GetAllTextResults.argtypes = [c_void_p, POINTER(POINTER(TextResultArray))]
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DBR_GetAllTextResults.restype = c_int
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ret = DBR_GetAllTextResults(instance, byref(pResults))
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print('DBR_GetAllTextResults: {}'.format(ret))
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if ret != 0 or pResults.contents.resultsCount == 0:
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print("No barcode found.")
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else:
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print(f"Total barcode(s) found: {pResults.contents.resultsCount}")
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for i in range(pResults.contents.resultsCount):
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result = pResults.contents.results[i]
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print(result)
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print(f"Barcode {i+1}:")
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# crash
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# print(result.contents)
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# print(f" Type: {result.contents.barcodeFormatString.decode('utf-8')}")
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# print(f" Text: {result.contents.barcodeText.decode('utf-8')}")
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# DBR_FreeTextResults
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DBR_FreeTextResults = dbr.DBR_FreeTextResults
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DBR_FreeTextResults.argtypes = [POINTER(POINTER(TextResultArray))]
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DBR_FreeTextResults.restype = None
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if bool(pResults):
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DBR_FreeTextResults(byref(pResults))
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####################################################################################
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# DBR_DestroyInstance
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DBR_DestroyInstance = dbr.DBR_DestroyInstance
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DBR_DestroyInstance.argtypes = [c_void_p]
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DBR_DestroyInstance(instance)

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