Create a watermark for images using C++

A guide on how to create a watermark for images in C++ using the OpenCV library. This article helps you understand how to add text or images onto a photo to create a watermark.

In this article, we will explore how to create a watermark for images using C++ through the OpenCV library. You will learn how to use OpenCV functions to overlay text or images onto a base photo.

C++ code

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

using namespace cv;

int main() {
    // Read image
    Mat image = imread("input.jpg");
    if (image.empty()) {
        std::cout << "Cannot open or find the image!" << std::endl;
        return -1;
    }

    // Set watermark text
    std::string watermark = "Watermark";
    int fontFace = FONT_HERSHEY_SIMPLEX;
    double fontScale = 2;
    int thickness = 3;
    Scalar color(255, 255, 255); // White color

    // Calculate position to place the watermark
    int baseline = 0;
    Size textSize = getTextSize(watermark, fontFace, fontScale, thickness, &baseline);
    Point textOrg(image.cols - textSize.width - 10, image.rows - baseline - 10);

    // Add watermark to image
    putText(image, watermark, textOrg, fontFace, fontScale, color, thickness);

    // Save the image with watermark
    imwrite("output.jpg", image);

    // Display the image
    imshow("Image with watermark", image);
    waitKey(0);

    return 0;
}

Detailed explanation

• #include <opencv2/opencv.hpp>: OpenCV library for image processing.
• Mat image = imread("input.jpg");: Read an image from the file.
• if (image.empty()) {...}: Check if the image was successfully opened.
• std::string watermark = "Watermark";: Set the watermark text.
• getTextSize(...): Calculate the size of the watermark text for alignment.
• Point textOrg(...): Calculate the position to place the watermark at the bottom right corner.
• putText(...): Overlay the watermark text onto the image.
• imwrite("output.jpg", image);: Save the image with the watermark to a new file.
• imshow(...): Display the image with the watermark.
• waitKey(0);: Wait for a key press to close the display window.

System Requirements:

• C++ version: C++11 or later
• OpenCV library: Installation of OpenCV is required
• Compiler: GCC, Clang, MSVC, or any compiler that supports C++11 or later

How to install the libraries:

1. Download and install OpenCV from the official OpenCV site.
2. Set up environment variables and configure your compiler to use OpenCV in your project.

Tips:

• Make sure that the position and size of the watermark are appropriate for the original image. You can adjust parameters to achieve better effects.

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