OpenCV中imread/imwrite与imdecode/imencode的异同

OpenCV中的cv::imdecode函数是从指定的内存缓存中读一幅图像，而cv::imencode是将一幅图像写进内存缓存中。cv::imread是从指定文件载入一幅图像，cv::imwrite是保存一幅图像到指定的文件中。

         cv::imread和cv::imdecode内部都是通过ImageDecoder类来进行图像解码的。cv::write和cv::encode内部都是通过ImageEncoder类来进行图像编码的。

以下是测试代码：

#include "funset.hpp"#include <string>#include <fstream>#include <vector>#include <opencv2/opencv.hpp>int test_encode_decode(){// cv::imread/cv::imwritestd::string image_name = "E:/GitCode/OpenCV_Test/test_images/1.jpg";cv::Mat mat1 = cv::imread(image_name, 1);if (mat1.empty()) {fprintf(stderr, "read image fail: %s\n", image_name.c_str());return -1;}std::string save_image = "E:/GitCode/OpenCV_Test/test_images/1_1.jpg";cv::imwrite(save_image, mat1);// cv::imdecode/cv::imencodestd::ifstream file(image_name.c_str(), std::ios::in | std::ios::binary | std::ios::ate);if (!file.is_open()) {fprintf(stderr, "open file fail: %s\n", image_name.c_str());return -1;}std::streampos size = file.tellg();file.seekg(0, std::ios::beg);std::string buffer(size, ' ');file.read(&buffer[0], size);file.close();std::vector<char> vec_data(&buffer[0], &buffer[0] + size);cv::Mat mat2 = cv::imdecode(vec_data, 1);std::string save_image2 = "E:/GitCode/OpenCV_Test/test_images/2_1.jpg";cv::imwrite(save_image2, mat2);std::vector<uchar> buf;cv::imencode(".jpg", mat1, buf);std::string save_image3 = "E:/GitCode/OpenCV_Test/test_images/2_2.jpg";std::ofstream file2(save_image3.c_str(), std::ios::out | std::ios::binary);if (!file2) {fprintf(stderr, "open file fail: %s\n", save_image3.c_str());return -1;}file2.write((char*)&buf[0], buf.size()*sizeof(uchar));file2.close();cv::Mat image1 = cv::imread(save_image, 1);cv::Mat image2 = cv::imread(save_image2, 1);cv::Mat image3 = cv::imread(save_image3, 1);if (!image1.data || !image2.data || !image3.data) {fprintf(stderr, "read image fail\n");return -1;}if (image1.rows != image2.rows || image1.cols != image2.cols ||image1.rows != image3.rows || image1.cols != image3.cols ||image1.step != image2.step || image1.step != image3.step) {fprintf(stderr, "their size are different\n");return -1;}for (int h = 0; h < image1.rows; ++h) {const uchar* p1 = image1.ptr(h);const uchar* p2 = image2.ptr(h);const uchar* p3 = image3.ptr(h);for (int w = 0; w < image1.cols; ++w) {if (p1[w] != p2[w] || p1[w] != p3[w]) {fprintf(stderr, "their value are different\n");return -1;}}}fprintf(stdout, "test image encode/decode, imread/imwrite finish\n");return 0;}

测试结果如下图：

GitHub：https://github.com/fengbingchun/OpenCV_Test