Let's talk about how to remove image watermarks in Node.js

In web development, picture materials are essential, and some pictures may have watermarks. At this time, we need to use some tools to remove them. This article will introduce how to remove image watermarks using Node.js.

1. Understanding Node.js

Node.js is a JavaScript running environment based on the Chrome V8 engine. It is an open source, cross-platform JavaScript running environment that allows JavaScript to run on the server side. Node.js has extremely high operating efficiency and supports asynchronous I/O and event-driven features, making it excellent at handling high concurrency and a large number of I/O operations. At the same time, Node.js has a rich module library that can easily implement various functions.

2. Use the Jimp library

A common method to remove image watermarks in Node.js is to use the Jimp library, which is a pure JavaScript library for image processing. Using the Jimp library, we can easily perform operations such as cutting, scaling, rotating, inverting, and adding filters to images. Here, we focus on how to remove image watermarks using the Jimp library.

1. Install Jimp library

Run the following command in the command line to install Jimp library:

npm install jimp --save

2. Remove image watermark

The method of using the Jimp library to remove image watermarks is as follows:

const Jimp = require('jimp');

// 读取原图
Jimp.read('source.png').then(image => {
  // 读取水印图
  Jimp.read('watermark.png').then(watermark => {
    // 获取原图和水印图的宽高
    const width = image.bitmap.width;
    const height = image.bitmap.height;
    const wmWidth = watermark.bitmap.width;
    const wmHeight = watermark.bitmap.height;

    // 计算水印宽高缩放比例
    const scale = width / wmWidth;

    // 缩放水印图
    watermark.scale(scale);

    // 将水印图绘制到原图上
    image.composite(watermark, 0, 0, {
      mode: Jimp.BLEND_SOURCE_OVER,
      opacitySource: 1,
      opacityDest: 1
    });

    // 保存处理后的图片
    image.write('result.png');
  });
});

In the above code, we first read the original image and watermark image, and then obtain their width, height and scaling ratio to watermark The image is zoomed. Then, use the composite() method to draw the watermark image onto the original image, and specify the composition mode and opacity. Finally, save the processed image.

3. Summary

By using Node.js and Jimp library, we can easily remove image watermarks. Of course, for some special watermark processing, we can also use other image processing libraries, such as GraphicsMagick, ImageMagick, etc., which provide more image processing functions.

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