opencv imencode和imdecode使用，用于网络传输图片

http://blog.csdn.net/tt_ren/article/details/53227900

程序首先读入一个图片。然后encode，之后把encode后的内容写入文件（实际应用可以发送到网络）。
第二步，从文件读取encode的内容。然后解码decode。转换为mat格式，显示出来。

#include <boost/filesystem.hpp>
#include <boost/filesystem/fstream.hpp>
#include <iostream>
#include <sstream>
#include <string>
#include <opencv2/opencv.hpp>
#include <vector>

using namespace boost::filesystem;
namespace newfs = boost::filesystem;
using namespace cv;

int main(int argc, char ** argv)
{
    cv::Mat img_encode;
    img_encode = imread("../res/test.png", CV_LOAD_IMAGE_COLOR);

    //encode image and save to file
    std::vector<uchar> data_encode;
    imencode(".png", img_encode, data_encode);
    //同样一张图片, 用BMP=10.6K  PNG=39.2K  JPG=9K. 网络不好建议用JPG, 追求清晰和带宽用PNG
    std::string str_encode(data_encode.begin(), data_encode.end());

    path p("../res/imgencode_cplus.txt");
    newfs::ofstream ofs(p);
    assert(ofs.is_open());
    ofs << str_encode;
    ofs.flush();
    ofs.close();

    //read image encode file and display
    newfs::fstream ifs(p);
    assert(ifs.is_open());
    std::stringstream sstr;
    while(ifs >> sstr.rdbuf());
    ifs.close();

    Mat img_decode;
    std::string str_tmp = sstr.str();
    std::vector<uchar> data(str_tmp.begin(), str_tmp.end());
    img_decode = imdecode(data, CV_LOAD_IMAGE_COLOR);
    imshow("pic",img_decode);
    cvWaitKey(10000);

    return 0;
}

//python
import sys
import cv2
import numpy as np
def img_endecode( img):
    #type img: cv::mat
    #encode image from cv::mat
    img_encode = cv2.imencode('.png', img)[1]
    data_encode = np.array(img_encode)
    str_encode = data_encode.tostring()

    #save to file
    fw = open('img_encode.txt', 'w')
    fw.write(str_encode)
    fw.flush
    fw.close

    #decode and display
    nparr = np.fromstring(str_encode, np.uint8)
    img_decode = cv2.imdecode(nparr, 1)
    cv2.imshow("img_decode", img_decode)
    cv2.waitKey(10000)