node-pnglib 
Pure Javascript lib for generate PNG, Node.js version for PNGlib.
Installation
npm install node-pnglib
Example
Test it with http server:
const http = require('http');
const PNGlib = require('node-pnglib');
http.createServer(function (req, res) {
if(req.url == '/favicon.ico') return res.end('');
// width 100, height 40
let png = new PNGlib(100, 40);
// from (0, 20)
let lineIndex = png.index(0, 20);
for (let i = 0; i < 100; i++) {
// draw a line to (0, 75)
png.buffer[lineIndex + i] = png.color('blue');
}
res.setHeader('Content-Type', 'image/png');
res.end(png.getBuffer());
}).listen(3001);Output:
Test with file:
const fs = require('fs');
const PNGlib = require('node-pnglib');
let png = new PNGlib(150, 150);
for (let i = 20; i < 100; i++) {
for (let j = 20; j < 100; j++) {
png.setPixel(i + 10, j + 25, '#cc0044');
png.setPixel(i + 20, j + 10, '#0044cc');
png.setPixel(i + 30, j, '#00cc44');
}
}
fs.writeFileSync('./block.png', png.getBuffer());Output:
Let's try to draw waves:
const http = require('http');
const PNGlib = require('node-pnglib');
http.createServer(function (req, res) {
if(req.url == '/favicon.ico') return res.end('');
let png = new PNGlib(100, 100);
for (let i = 0; i < 65; i++) {
for (let j = 10; j < 65; j++) {
png.setPixel(i + 10, j + 20, '#cc0044');
png.setPixel(i + 20, j + 10, '#0044cc');
png.setPixel(i + 30, j, '#00cc44');
}
}
res.setHeader('Content-Type', 'image/png');
res.end(png.getBuffer());
}).listen(3001);Output:
Benchmark
# Simple line
pnglib x 1,021 ops/sec ±3.37% (76 runs sampled)
pnglib-es6 x 3,293 ops/sec ±4.79% (79 runs sampled)
node-pnglib x 17,027 ops/sec ±0.93% (87 runs sampled)
Fastest is node-pnglib
node v8.1.1
MacBook Pro (Retina, 13-inch, Early 2015)
2.7 GHz Intel Core i5
It's faster than similar libraries. you can go to here for more benchmark infomation.
