How can I Construct key pair values using strings in CPP? - c++

Question

I used poco json for key pair values, and it consuming more time(Sending Images consuming more time).
std::vector<unsigned char> buff, buff1;
cv::imencode(".png", image1, buff);
cv::imencode(".png", image2, buff1);
Poco::JSON::Object obj;
obj.set("photo1", buff);
obj.set("photo2", buff1);
std::stringstream ss;
obj.stringify(ss);
I want to construct same in terms of string in CPP.
cv::imencode(".png", image1, buff);
cv::imencode(".png", image2, buff1);
std::string data ="{\"photo1\":" +std::string(buff.begin(),buff.end());
data .append(",");
data.append("\"photo2"\":" + std::string(buff1.begin(),buff1.end()));
data.append("}");
If I Done step 2 How can i extract back the imencode data.
I tried converting json string.
a) imencode-> string -> stringstream.
I want to construct key pair value in terms of string.
Minimal Code
std::string stringifyTheBothImages(cv::Mat image, cv::Mat image1) {
std::ostringstream ostr;
std::vector<unsigned char> buffer, buffer1;
cv::imencode(".png", image, buffer);
std::string address_json = "{\"photo1\":" + data;
address_json.append(",");
address_json.append("\"photo2\":" + data);
address_json.append("}");
return address_json;
}
int main(){
cv::Mat image =
cv::imread("C:/Amar/dec_16_2022_slabs/train/class0/image0.png", 1);
data2 = stringifyTheBothImages(image, image);
Poco::JSON::Parser parser;
auto result = parser.parse(data2);
Poco::JSON::Object::Ptr ptr_object =
result.extract<Poco::JSON::Object::Ptr>();
std::cout << ptr_object->get("photo1").toString() << std::endl;
}

Answer 1

Since with JSON method you get an array of numbers for both the keys, you can do similar in C++ by converting each value in the buffer to an integer.
Also, instead of using string::append use stringstream.
#include <iostream>
#include <vector>
#include <sstream>
int main()
{
std::vector<uint8_t> buffer1 = {129, 0, 234, 231, 255, 234, 13, 134, 2};
std::vector<uint8_t> buffer2 = {109, 0, 204, 201, 205, 204, 10, 104, 4};
std::stringstream ss;
ss << "{\"photo1\":[";
for (size_t i = 0; i < buffer1.size(); i++)
{
ss << static_cast<int>(buffer1[i]);
if (i != buffer1.size() - 1)
ss << ',';
}
ss << "],\"photo2\":[";
for (size_t i = 0; i < buffer2.size(); i++)
{
ss << static_cast<int>(buffer2[i]);
if (i != buffer2.size() - 1)
ss << ',';
}
ss << "]}";
std::cout << ss.str();
}