C++ JPG to Mat Conversion: OpenCV & Boost.GIL Examples

JPG is a compressed format, requiring third-party libraries for reading and processing. In C++, popular choices include OpenCV and Boost.GIL.

Using OpenCV

#include <opencv2/opencv.hpp>

using namespace cv;

int main() {
    // Read JPG image
    Mat image = imread('example.jpg', IMREAD_COLOR);
    if (image.empty()) {
        printf("Could not read the image: %s\n", "example.jpg");
        return -1;
    }

    // Display image
    namedWindow('JPG Image', WINDOW_NORMAL);
    imshow('JPG Image', image);

    waitKey(0);

    return 0;
}

This code reads the JPG image using imread(), stores it in a Mat variable, displays it in a window using namedWindow() and imshow(), and waits for user input with waitKey().

Using Boost.GIL

#include <iostream>
#include <boost/gil/extension/io/jpeg_dynamic_io.hpp>
#include <boost/gil/image.hpp>
#include <boost/gil/typedefs.hpp>

using namespace boost::gil;

int main() {
    // Read JPG image
    rgb8_image_t image;
    jpeg_read_image('example.jpg', image);

    // Display image size
    std::cout << "Image size: " << image.dimensions() << std::endl;

    return 0;
}

This example demonstrates reading the JPG image into a rgb8_image_t using jpeg_read_image() and then printing the image dimensions.

Choose the library that best suits your project needs. Both OpenCV and Boost.GIL offer comprehensive image processing functionalities.