图像识别 C++ API接口调用（调用篇01）
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同步链接地址：https://yangshun.win/blogs/cd08a730/
通用物体和场景识别高级版 - C++ 简单调用
目前通用物体和场景识别支持超过 10 万类常见物体和场景识别，接口返回图片内 1 个或多个物体的名称，并可获取百科信息。适用于图像或视频内容分析、拍照识图等业务场景。
功能介绍
1. 识别物体或场景名称
支持识别动物、植物、商品、建筑、风景、动漫、食材、公众人物等 10 万个常见物体及场景，接口返回大类及细分类的名称结果。
2. 获取百科信息
支持获取图片识别结果对应的百科信息，接口返回百科词条 URL、图片和摘要描述，可选择是否需要返回百科信息。
应用场景
- 图片内容分析与推荐：对用户浏览的图片或观看的视频内容进行识别，根据识别结果给出相关内容推荐或广告展示。广泛应用于新闻资讯类、视频类 app 等内容平台中
- 拍照识图：根据用户拍摄照片，识别图片中物体名称及百科信息，提高用户交互体验，广泛应用于智能手机厂商、拍照识图及科普类 app 中
- 拍照闯关趣味营销：设计线上营销活动，根据用户拍摄照片，自动识别图片中物体信息是否符合活动要求，提升用户交互体验，减少人工审核成本
接口描述
该请求用于通用物体及场景识别，即对于输入的一张图片（可正常解码，且长宽比适宜），输出图片中的多个物体及场景标签。
请求说明
- HTTP 方法： POST
- 请求 URL： https://aip.baidubce.com/rest/2.0/image-classify/v2/advanced_general
- URL参数： access_token
- Header 参数： Content-Type = application/x-www-form-urlencoded
- Body 参数：见下表
返回说明
返回参数如下表：
返回示例如下：
{
"log_id": "4269290077301074002",
"result_num": 5,
"result": [
{
"score": 0.203018,
"root": "植物-树",
"baike_info": {
"baike_url": "http://baike.baidu.com/item/%E6%A0%91/2699484",
"image_url": "http://imgsrc.baidu.com/baike/pic/item/6159252dd42a2834218a2c2154b5c9ea15cebfef.jpg",
"description": "树状图是一种数据结构，它是由n(n>=1)个有限结点组成一个具有层次关系的集合。把它叫做“树”是因为它看起来像一棵倒挂的树，也就是说它是根朝上，而叶朝下的。它具有以下的特点：每个结点有零个或多个子结点；没有父结点的结点称为根结点；每一个非根结点有且只有一个父结点；除了根结点外，每个子结点可以分为多个不相交的子树；"
},
"keyword": "树"
},
{
"score": 0.15084,
"root": "自然风景-其他",
"keyword": "风景"
},
{
"score": 0.100728,
"root": "自然风景-天空",
"keyword": "天空"
},
{
"score": 0.052704,
"root": "商品-工艺品",
"keyword": "工艺品"
},
{
"score": 0.003729,
"root": "商品-工艺品",
"keyword": "佛像"
}
]
}
C++ 代码实现调用
这里假设已经将环境配置好了，环境配置的文章可以参考 Windows 下使用 Vcpkg 配置百度 AI 图像识别 C++开发环境(VS2017)。
为了方便，首先根据返回参数定义了一个结构体，该结构体包括了返回参数中的参数，如下：
struct GeneralInfo {
std::string keyword;
float score;
std::string root;
std::string baikeurl;
std::string imageurl;
std::string baikedesc;
void print() {
std::cout << std::setw(30) << std::setfill('-') << '\n';
std::cout << "keyword: " << keyword << "\n";
std::cout << "score: " << std::fixed << std::setprecision(4) << score << "\n";
std::cout << "root: " << root << "\n";
if (baikeurl != "null")
std::cout << "baikeurl: " << baikeurl << "\n";
if (imageurl != "null")
std::cout << "imageurl: " << imageurl << "\n";
if (baikedesc != "null")
std::cout << "baikedesc: " << baikedesc << "\n";
}
};
然后定义了一个类来调用接口并获取结果
class General
{
public:
General();
~General();
Json::Value request(std::string imgBase64, std::map& options);
int getResultNum();
// get all return results
void getAllResult(std::vector& results);
// only get first result
void getResult(GeneralInfo& result);
private:
Json::Value obj_;
std::string url_;
uint32_t result_num_;
// file to save token key
std::string filename_;
};
类中的私有成员 obj_ 表示返回结果对应的 json 对象。url_ 表示请求的 url，result_num_ 表示返回结果数，filename_ 表示用于存储 access token 的文件的文件名。
getAllResult 将所有返回结果存放到一个 vector 中。getResult 只返回第一条结果，也就是分数最高的结果。
完整代码如下
General.h 代码如下：
#pragma once
#include "util.h"
struct GeneralInfo {
std::string keyword;
float score;
std::string root;
std::string baikeurl;
std::string imageurl;
std::string baikedesc;
void print() {
std::cout << std::setw(30) << std::setfill('-') << '\n';
std::cout << "keyword: " << keyword << "\n";
std::cout << "score: " << std::fixed << std::setprecision(4) << score << "\n";
std::cout << "root: " << root << "\n";
if (baikeurl != "null")
std::cout << "baikeurl: " << baikeurl << "\n";
if (imageurl != "null")
std::cout << "imageurl: " << imageurl << "\n";
if (baikedesc != "null")
std::cout << "baikedesc: " << baikedesc << "\n";
}
};
class General
{
public:
General();
~General();
Json::Value request(std::string imgBase64, std::map& options);
int getResultNum();
// get all return results
void getAllResult(std::vector& results);
// only get first result
void getResult(GeneralInfo& result);
private:
Json::Value obj_;
std::string url_;
uint32_t result_num_;
// file to save token key
std::string filename_;
};
void generalTest();
General.cpp 代码如下：
#include "General.h"
General::General()
{
filename_ = "tokenKey";
url_ = "https://aip.baidubce.com/rest/2.0/image-classify/v2/advanced_general";
}
General::~General()
{
}
Json::Value General::request(std::string imgBase64, std::map& options)
{
std::string response;
Json::Value obj;
std::string token;
// 1. get HTTP post body
std::string body;
mergeHttpPostBody(body, imgBase64, options);
// 2. get HTTP url with access token
std::string url = url_;
getHttpPostUrl(url, filename_, token);
// 3. post request, response store the result
int status_code = httpPostRequest(url, body, response);
if (status_code != CURLcode::CURLE_OK) {
obj["curl_error_code"] = status_code;
obj_ = obj;
return obj; // TODO: maybe should exit
}
// 4. make string to json object
generateJson(response, obj);
// if access token is invalid or expired, we will get a new one
if (obj["error_code"].asInt() == 110 || obj["error_code"].asInt() == 111) {
token = getTokenKey();
writeFile(filename_, token);
return request(imgBase64, options);
}
obj_ = obj;
checkErrorWithExit(obj);
result_num_ = getResultNum();
return obj;
}
int General::getResultNum()
{
return obj_["result_num"].asInt();
}
void General::getAllResult(std::vector& results)
{
results.reserve(result_num_);
GeneralInfo tmp;
for (uint32_t i = 0; i < result_num_; ++i) {
tmp.keyword = UTF8ToGB(obj_["result"][i]["keyword"].asString().c_str());
tmp.score = obj_["result"][i]["score"].asFloat();
tmp.root = UTF8ToGB(obj_["result"][i]["root"].asString().c_str());
tmp.baikeurl = obj_["result"][i]["baike_info"].get("baike_url", "null").asString();
tmp.imageurl = obj_["result"][i]["baike_info"].get("image_url", "null").asString();
tmp.baikedesc = UTF8ToGB(obj_["result"][i]["baike_info"].get("description", "null").asString().c_str());
results.push_back(tmp);
}
}
void General::getResult(GeneralInfo& result)
{
result.keyword = UTF8ToGB(obj_["result"][0]["keyword"].asString().c_str());
result.score = obj_["result"][0]["score"].asFloat();
result.root = UTF8ToGB(obj_["result"][0]["root"].asString().c_str());
result.baikeurl = obj_["result"][0]["baike_info"].get("baike_url", "null").asString();
result.imageurl = obj_["result"][0]["baike_info"].get("image_url", "null").asString();
result.baikedesc = UTF8ToGB(obj_["result"][0]["baike_info"].get("description", "null").asString().c_str());
}
void generalTest()
{
std::cout << "size: " << sizeof(GeneralInfo) << "\n";
// read image and encode to base64
std::string imgFile = "./images/cat.jpg";
std::string imgBase64;
imgToBase64(imgFile, imgBase64);
// set options
std::map options;
options["baike_num"] = "5";
Json::Value obj;
General generalObj;
obj = generalObj.request(imgBase64, options);
GeneralInfo result;
generalObj.getResult(result);
result.print();
std::vector results;
generalObj.getAllResult(results);
for (auto & vec : results) {
vec.print();
}
}
util.h 代码如下：
#pragma once #include #include #include #include #include #include #include #include #include "base64.h" size_t writeCallback(void *ptr, size_t size, size_t nmemb, void *userdata); std::string getTokenKey(); int readImageFile(const char *filename, std::string& out); void imgToBase64(std::string &imgFile, std::string &imgBase64); int writeFile(const std::string & fileString, const std::string &str); int readFile(const std::string & fileString, std::string &str); std::string UTF8ToGB(const char* str); void mergeHttpPostBody(std::string &body, std::string imgBase64, std::map& options); void getHttpPostUrl(std::string &url, std::string &filename, std::string &token); int httpPostRequest(std::string &url, std::string &body, std::string &response); void generateJson(std::string &response, Json::Value &obj); void checkErrorWithExit(Json::Value &obj);
util.cpp 代码如下：
#include "util.h"
// callback function for curl
size_t writeCallback(void *ptr, size_t size, size_t nmemb, void *userdata)
{
std::string *str = dynamic_cast((std::string *)userdata);
str->append((char *)ptr, size * nmemb);
return size * nmemb;
}
// get access token from server by get method
std::string getTokenKey() {
std::string url = "https://aip.baidubce.com/oauth/2.0/token";
std::string apikey = "FP6E0dqEnGTPAXMYpUDXW7tb";
std::string secritkey = "MoNhkCh3VhtXpMft7Xoj4hQy4iHVbNZu";
std::map params;
std::string response;
params["grant_type"] = "client_credentials";
params["client_id"] = apikey;
params["client_secret"] = secritkey;
// append url with parameters
for (auto it = params.begin(); it != params.end(); ++it) {
url += (it == params.begin() ? "?" : "&") + it->first + "=" + it->second;
}
CURL *curl = curl_easy_init();
struct curl_slist * slist = NULL;
curl_easy_setopt(curl, CURLOPT_URL, url.c_str());
curl_easy_setopt(curl, CURLOPT_HTTPHEADER, slist);
curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, writeCallback); // set callback function
curl_easy_setopt(curl, CURLOPT_WRITEDATA, &response); // set var to receive return info from callback function
curl_easy_setopt(curl, CURLOPT_NOSIGNAL, true);
curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, false);
curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, false);
curl_easy_setopt(curl, CURLOPT_VERBOSE, false);
int status_code = curl_easy_perform(curl);
curl_easy_cleanup(curl);
curl_slist_free_all(slist);
Json::Value obj;
if (status_code != CURLcode::CURLE_OK) {
obj["curl_error_code"] = status_code;
return obj.toStyledString();
}
// parse json string
JSONCPP_STRING error;
Json::CharReaderBuilder builder;
const std::unique_ptr reader(builder.newCharReader());
reader->parse(response.data(), response.data() + response.size(), &obj, &error);
std::string access_token = obj["access_token"].asString();
return access_token;
}
// read image file [https://stackoverflow.com/questions/9612121/how-to-read-image-files-and-store-it-in-memorystdstring-in-c]
int readImageFile(const char *filename, std::string& out) {
std::ifstream in(filename, std::ios::in | std::ios::binary);
if (in) {
std::ostringstream oss;
oss << in.rdbuf();
out.assign(oss.str());
return 0;
}
else {
std::cerr << "Can't open image!" << std::endl;
return -1;
}
}
void imgToBase64(std::string &imgFile, std::string &imgBase64) {
// read image and encode to base64
std::string out;
readImageFile(imgFile.c_str(), out);
imgBase64 = base64_encode(out.c_str(), (int)out.size());
}
int writeFile(const std::string & fileString, const std::string &str) {
std::ofstream out(fileString, std::ios::binary);
if (out.is_open()) {
out << str;
out.close();
}
return 0;
}
int readFile(const std::string & fileString, std::string &str) {
std::ifstream in(fileString);
if (!in.is_open()) {
str = "";
return -1;
}
char buffer[256];
while (!in.eof()) {
in.getline(buffer, sizeof(buffer));
}
str = buffer;
return 0;
}
std::string UTF8ToGB(const char* str)
{
std::string result;
WCHAR *strSrc;
LPSTR szRes;
int i = MultiByteToWideChar(CP_UTF8, 0, str, -1, NULL, 0);
strSrc = new WCHAR[i + 1];
MultiByteToWideChar(CP_UTF8, 0, str, -1, strSrc, i);
i = WideCharToMultiByte(CP_ACP, 0, strSrc, -1, NULL, 0, NULL, NULL);
szRes = new CHAR[i + 1];
WideCharToMultiByte(CP_ACP, 0, strSrc, -1, szRes, i, NULL, NULL);
result = szRes;
delete[]strSrc;
delete[]szRes;
return result;
}
void mergeHttpPostBody(std::string &body, std::string imgBase64, std::map& options) {
body = "image=" + std::string(curl_escape(imgBase64.c_str(), int(imgBase64.size()))) + "&";
// append body with options
for (auto it = options.begin(); it != options.end(); ++it) {
body += std::string(curl_escape(it->first.c_str(), (int)it->first.size()))
+ "=" + std::string(curl_escape(it->second.c_str(), (int)it->second.size())) + "&";
}
}
// first get token from file (if exist), then add token to url
void getHttpPostUrl(std::string &url, std::string &filename, std::string &token) {
// if token file is not exist, a new one should be create
if (readFile(filename, token) < 0) {
token = getTokenKey();
writeFile(filename, token);
}
url = url + "?access_token=" + token;
}
int httpPostRequest(std::string &url, std::string &body, std::string &response) {
struct curl_slist * slist = NULL;
CURL *curl = curl_easy_init();
// set headers, actually this is used by default
std::string headers = "Content-Type:application/x-www-form-urlencoded";
slist = curl_slist_append(slist, headers.c_str());
curl_easy_setopt(curl, CURLOPT_URL, url.c_str());
curl_easy_setopt(curl, CURLOPT_HTTPHEADER, slist);
curl_easy_setopt(curl, CURLOPT_POST, true);
curl_easy_setopt(curl, CURLOPT_POSTFIELDS, body.data());
curl_easy_setopt(curl, CURLOPT_POSTFIELDSIZE, body.size());
curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, writeCallback);
curl_easy_setopt(curl, CURLOPT_WRITEDATA, (void *)&response);
curl_easy_setopt(curl, CURLOPT_NOSIGNAL, true);
curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, false);
curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, false);
curl_easy_setopt(curl, CURLOPT_VERBOSE, false);
int status_code = curl_easy_perform(curl);
curl_easy_cleanup(curl);
curl_slist_free_all(slist);
return status_code;
}
void generateJson(std::string &response, Json::Value &obj) {
// parse json string
JSONCPP_STRING error;
Json::CharReaderBuilder builder;
const std::unique_ptr reader(builder.newCharReader());
reader->parse(response.data(), response.data() + response.size(), &obj, &error);
}
void checkErrorWithExit(Json::Value &obj)
{
if (obj.get("error_code", "null")) {
std::cerr << obj.get("error_code", "null") << " : " << obj.get("error_msg", "null") << std::endl;
system("pause");
exit(EXIT_FAILURE);
}
}
运行结果
测试图像
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