opencv的Mat資料和JPG資料的相互轉化，及base64資料流的轉化
阿新 • • 發佈：2022-05-15
轉載：https://blog.csdn.net/baidu_31872269/article/details/86010156
Mat 一個影象資料轉化為jpg圖片buffer 壓縮率可以變為原來的 1/ 15 - 1 / 10
Mat2Img.h
#ifndef MAT2IMG_H #define MAT2IMG_H #include "opencv2/opencv.hpp" #include <vector> #include "image_base64.h" class Mat2Img { public: static int MatToByteArray(constcv::Mat mat, std::vector<unsigned char>& buff) { if (mat.empty()) { return 0; } std::vector<int> param = std::vector<int>(2); param[0] = CV_IMWRITE_JPEG_QUALITY; param[1] = 95; // default(95) 0-100 cv::imencode(".jpg", mat, buff, param);return 0; } static int JPEGToMat(cv::Mat &matImage, std::vector<unsigned char> buff) { if (buff.empty()) { return -1; } if ((buff[0] == 0xFF && buff[1] == 0xD8)) { matImage = cv::imdecode(buff, CV_LOAD_IMAGE_COLOR); }else { buff.insert(buff.begin(), 0xFF); buff.insert(buff.begin()+1, 0xD8); matImage = cv::imdecode(buff, CV_LOAD_IMAGE_COLOR); } return 0; } static int Mat2Base64(cv::Mat &image, std::string &base64) { std::vector<unsigned char> cut_jpg; // Mat -> jpg cut_jpg.clear(); Mat2Img::MatToByteArray(image, cut_jpg); base64 = ImageBase64::encode(cut_jpg.data(), cut_jpg.size()); return 0; } static int Base2Mat(std::string &base64, cv::Mat &image) { int outLen = 0; std::string str1 = ImageBase64::decode(base64.c_str(), base64.size(), outLen); std::vector<uchar> baseJpgVec; baseJpgVec.assign(&str1.data()[0], &str1.data()[outLen]); int ret = Mat2Img::JPEGToMat(image, baseJpgVec); if (ret != 0) { return ret; } return 0; } }; #endif
有時候也會用到jpg 資料轉化為Base64 的字串資料，方便網路傳輸
image_base64.h
#ifndef TESTFACEAPI_TESTFACEAPI_IMAGE_BASE64_H #define TESTFACEAPI_TESTFACEAPI_IMAGE_BASE64_H #include <string> // 對圖片進行base64編碼解碼類 class ImageBase64 { public: /*編碼 DataByte [in]輸入的資料長度,以位元組為單位 */ static const std::string encode(const unsigned char* Data, int DataByte); /*解碼 DataByte [in]輸入的資料長度,以位元組為單位 OutByte [out]輸出的資料長度,以位元組為單位,請不要通過返回值計算 輸出資料的長度 */ static const std::string decode(const char* Data, int DataByte, int& OutByte); // 傳入圖片地址進行base64編碼示例 static std::string file2base64(const std::string& file_path); }; #endif
image_base64.cpp
#include "image_base64.h" #include <vector> #include "opencv2\opencv.hpp" static const std::string base64_chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ" "abcdefghijklmnopqrstuvwxyz" "0123456789+/"; static inline bool is_base64(unsigned char c) { return (isalnum(c) || (c == '+') || (c == '/')); } const std::string ImageBase64::encode(const unsigned char* Data, int DataByte) { //編碼表 const char EncodeTable[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"; //返回值 std::string str_encode; unsigned char tmp[4] = { 0 }; int line_length = 0; for (int i = 0; i < (int)(DataByte / 3); i++) { tmp[1] = *Data++; tmp[2] = *Data++; tmp[3] = *Data++; str_encode += EncodeTable[tmp[1] >> 2]; str_encode += EncodeTable[((tmp[1] << 4) | (tmp[2] >> 4)) & 0x3F]; str_encode += EncodeTable[((tmp[2] << 2) | (tmp[3] >> 6)) & 0x3F]; str_encode += EncodeTable[tmp[3] & 0x3F]; if (line_length += 4, line_length == 76) { str_encode += "\r\n"; line_length = 0; } } //對剩餘資料進行編碼 int mod = DataByte % 3; if (mod == 1) { tmp[1] = *Data++; str_encode += EncodeTable[(tmp[1] & 0xFC) >> 2]; str_encode += EncodeTable[((tmp[1] & 0x03) << 4)]; str_encode += "=="; } else if (mod == 2) { tmp[1] = *Data++; tmp[2] = *Data++; str_encode += EncodeTable[(tmp[1] & 0xFC) >> 2]; str_encode += EncodeTable[((tmp[1] & 0x03) << 4) | ((tmp[2] & 0xF0) >> 4)]; str_encode += EncodeTable[((tmp[2] & 0x0F) << 2)]; str_encode += "="; } return str_encode; } const std::string ImageBase64::decode(const char* Data, int DataByte, int& OutByte) { //解碼錶 const char DecodeTable[] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 62, // '+' 0, 0, 0, 63, // '/' 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, // '0'-'9' 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, // 'A'-'Z' 0, 0, 0, 0, 0, 0, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, // 'a'-'z' }; //返回值 std::string str_decode; int n_value = 0; int i = 0; while (i < DataByte) { if (*Data != '\r' && *Data != '\n') { n_value = DecodeTable[*Data++] << 18; n_value += DecodeTable[*Data++] << 12; str_decode += (n_value & 0x00FF0000) >> 16; OutByte++; if (*Data != '=') { n_value += DecodeTable[*Data++] << 6; str_decode += (n_value & 0x0000FF00) >> 8; OutByte++; if (*Data != '=') { n_value += DecodeTable[*Data++]; str_decode += n_value & 0x000000FF; OutByte++; } } i += 4; } else// 回車換行,跳過 { Data++; i++; } } return str_decode; } std::string ImageBase64::file2base64(const std::string& file_path) { cv::Mat img = cv::imread(file_path); if (img.empty()) { return ""; } std::vector<uchar> vec_img; //Mat 圖片資料轉換為vector<uchar> std::vector<int> vec_compression_params; vec_compression_params.push_back(CV_IMWRITE_JPEG_QUALITY); vec_compression_params.push_back(90); cv::imencode(".jpg", img, vec_img, vec_compression_params); // base64; std::string img_base64 = encode(vec_img.data(), vec_img.size()); return img_base64; }
main.cpp
int main(int argc, char * argv[]) { char * path1 = "C:\\Users\\FaceOS\\Pictures\\faceCheck\\20181207102753.jpg"; cv::Mat Image = cv::imread(path1); cv::imshow("show", Image); // Mat 轉化為jpg std::vector<unsigned char> buff_jpg; int ret = Mat2Img::MatToByteArray(Image, buff_jpg); // jpg 轉化為Base64 std::string str = ImageBase64::encode(buff_jpg.data(), buff_jpg.size()); // Base64 字串轉化為jpg 的string int outLen = 0; std::string str1 = ImageBase64::decode(str.c_str(), str.size(), outLen); cv::Mat MatFromBase; std::vector<uchar> baseJpgVec; // jpg string 拷貝到jpg 陣列buffer baseJpgVec.assign(&str1.data()[0], &str1.data()[outLen]); //jpg buffer 轉化為Mat Mat2Img::JPEGToMat(MatFromBase, baseJpgVec); cv::imshow("show1", MatFromBase); cv::waitKey(0); }