Create a Thumbnail for Images in C++

A detailed guide on how to create a thumbnail for images in C++ using the OpenCV library. This article will help you understand how to process images and easily resize them to create thumbnails.

In this article, we will learn how to create thumbnails for images using the OpenCV library in C++. We will load an image, resize it, and save the modified image as a new file.

C++ code

#include <opencv2/opencv.hpp>
#include <iostream>

int main() {
    // Read image from file
    cv::Mat image = cv::imread("input.jpg");
    
    // Check if the image is loaded successfully
    if (image.empty()) {
        std::cerr << "Cannot open or find the image file!" << std::endl;
        return -1;
    }

    // Create thumbnail with new size
    cv::Mat thumbnail;
    cv::resize(image, thumbnail, cv::Size(150, 150)); // Resize to 150x150

    // Save the thumbnail image
    cv::imwrite("thumbnail.jpg", thumbnail);

    std::cout << "Thumbnail created and saved successfully!" << std::endl;

    return 0;
}

Detailed explanation

• #include <opencv2/opencv.hpp>: Include the OpenCV library to use image processing functions.
• cv::imread("input.jpg"): Read the image from the file input.jpg.
• if (image.empty()) {...}: Check if the image was loaded successfully.
• cv::resize(image, thumbnail, cv::Size(150, 150));: Resize the image to 150x150 pixels to create a thumbnail.
• cv::imwrite("thumbnail.jpg", thumbnail);: Save the thumbnail image to the file thumbnail.jpg.
• std::cout << ...: Output a completion message to the console.

System Requirements:

• C++ version: C++11 or later
• Library: OpenCV (must be installed before compiling)
• Compiler: GCC, Clang, MSVC, or any compiler that supports C++11 or later

How to install OpenCV library:

1. Install on Ubuntu:

   sudo apt-get install libopencv-dev
   

2. Install on Windows:

   • Download OpenCV from the official site: https://opencv.org/releases/
   • Extract and configure the paths in your project.

Tips:

• Ensure that you have installed OpenCV correctly and configured the library paths in your development environment.
• You can change the thumbnail size by modifying the parameters in the cv::resize function according to your requirements.

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