在Node.js中读取PNG图像 [英] Reading a PNG image in Node.js

问题描述

Node.js中是否有一种简单的方法来读取PNG文件并获取图像的像素?类似 node-image 的东西，但是相反:)

Is there an easy way in Node.js to read a PNG file and get the pixels of the image? Something like node-image, but the other way :)

我浏览了 https://github.com/joyent/node/wiki/中列出的库modules#wiki-graphics ，但是它们要么是提供裁剪和调整大小的命令行工具的简单包装，要么是诸如node-canvas的复杂绘图工具.

I went through the libraries listed at https://github.com/joyent/node/wiki/modules#wiki-graphics, but they are either simple wrappers around command line tools providing cropping and resizing or complex drawing tools like node-canvas.

推荐答案

该程序无需本地依赖即可进行PNG解码和编码:

This one does both PNG decoding and encoding without native dependancies:

pngjs-Node.js的PNG编码器/解码器，没有本地依赖性.

反转PNG颜色的示例:

An example for inverting the colors of a PNG:

var fs = require('fs'),
PNG = require('pngjs').PNG;

fs.createReadStream('in.png')
  .pipe(new PNG())
  .on('parsed', function() {

    for (var y = 0; y < this.height; y++) {
        for (var x = 0; x < this.width; x++) {
            var idx = (this.width * y + x) << 2;

            // invert color
            this.data[idx] = 255 - this.data[idx];
            this.data[idx+1] = 255 - this.data[idx+1];
            this.data[idx+2] = 255 - this.data[idx+2];

            // and reduce opacity
            this.data[idx+3] = this.data[idx+3] >> 1;
        }
    }

    this.pack().pipe(fs.createWriteStream('out.png'));
});

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