node文字生成图片的示例代码

今天老板提了需求，要在服务端生成邀请卡，嗯…，简单的说就是把要这张：

变成差多这样的：

后端搞ruby的哥们搞了个html转图片，说转得太慢了，我就把这坑接下来了

所以睡前就倒腾了下，搞了个简单的实现

解决思路

文字转svg -> svg转png -> 合并图片

相关轮子

1. images Node.js 轻量级跨平台图像编解码库，不需要额外安装依赖
2. text-to-svg 文字转svg
3. svg2png svg转png图片

示例代码

'use strict';

const fs = require('fs');
const images = require('images');
const TextToSVG = require('text-to-svg');
const svg2png = require("svg2png");
const Promise = require('bluebird');

Promise.promisifyAll(fs);

const textToSVG = TextToSVG.loadSync('fonts/文泉驿微米黑.ttf');

const sourceImg = images('./i/webwxgetmsgimg.jpg');
const sWidth = sourceImg.width();
const sHeight = sourceImg.height();

const svg1 = textToSVG.getSVG('魏长青-人人讲App', {
 x: 0,
 y: 0,
 fontSize: 24,
 anchor: 'top',
});

const svg2 = textToSVG.getSVG('邀请您参加', {
 x: 0,
 y: 0,
 fontSize: 16,
 anchor: 'top',
});

const svg3 = textToSVG.getSVG('人人讲课程', {
 x: 0,
 y: 0,
 fontSize: 32,
 anchor: 'top',
});

Promise.coroutine(function* generateInvitationCard() {
 const targetImg1Path = './i/1.png';
 const targetImg2Path = './i/2.png';
 const targetImg3Path = './i/3.png';
 const targetImg4Path = './i/qrcode.jpg';
 const [buffer1, buffer2, buffer3] = yield Promise.all([
  svg2png(svg1),
  svg2png(svg2),
 svg2png(svg3),
 ]);

 yield Promise.all([
  fs.writeFileAsync(targetImg1Path, buffer1),
  fs.writeFileAsync(targetImg2Path, buffer2),
  fs.writeFileAsync(targetImg3Path, buffer3),
 ]);

 const target1Img = images(targetImg1Path);
 const t1Width = target1Img.width();
 const t1Height = target1Img.height();
 const offsetX1 = (sWidth - t1Width) / 2;
 const offsetY1 = 200;

 const target2Img = images(targetImg2Path);
 const t2Width = target2Img.width();
 const t2Height = target2Img.height();
 const offsetX2 = (sWidth - t2Width) / 2;
 const offsetY2 = 240;

 const target3Img = images(targetImg3Path);
 const t3Width = target3Img.width();
 const t3Height = target3Img.height();
 const offsetX3 = (sWidth - t3Width) / 2;
 const offsetY3 = 270;

 const target4Img = images(targetImg4Path);
 const t4Width = target4Img.width();
 const t4Height = target4Img.height();
 const offsetX4 = (sWidth - t4Width) / 2;
 const offsetY4 = 400;

 images(sourceImg)
 .draw(target1Img, offsetX1, offsetY1)
 .draw(target2Img, offsetX2, offsetY2)
 .draw(target3Img, offsetX3, offsetY3)
 .draw(target4Img, offsetX4, offsetY4)
 .save('./i/card.png', { quality : 90 });
})().catch(e => console.error(e));

注意事项

text-to-svg需要中文字体的支持，不然中文会乱码

在我的破电脑上执行一次只花了500多毫秒，感觉足够了，分享出来希望能给大家一个参照

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