node环境安装canvas并自定义字体

摘要：那便是极好的自定义字体不过可能会发现这是因为版本的没有这个函数。

为什么要在服务端装canvas？ 因为并不是所有的客户端都能很好的支持canvas（比如微信小程序不能修改自定义字体），所以我们需要一个
能够在服务端生成图片的，然后将图片传输

sudo apt-get install libcairo2-dev libjpeg8-dev libpango1.0-dev libgif-dev build-essential g++ -y

npm install -g canvas

var Canvas = require("canvas"),
    canvas = new Canvas(300, 200),
    ctx = canvas.getContext("2d"),
    fs = require("fs");
 
var out = fs.createWriteStream(__dirname + "/image.png")
  , stream = canvas.createPNGStream();
 
stream.on("data", function(chunk){
  out.write(chunk);
});
 
//在左边画正方形
ctx.fillStyle = "#A00"    
ctx.fillRect(0, 30,50,50);   
  
 
//在右边画正方形
ctx.fillStyle = "#aaa"    
ctx.fillRect(50, 30, 50, 50);
 
//画文字
ctx.fillStyle = "#000";
ctx.font = "20px Arial";
ctx.fillText("Hello World", 0, 20);
 
//画一个圆
ctx.beginPath();
ctx.arc(30, 110, 20, 0, 2*Math.PI);
ctx.stroke();
ctx.fillStyle = "green";                                                                                                                          
ctx.fill();
ctx.save();  

如果你按上述方法操作，并且运行成功了。那便是极好的

// You need to call it before the Canvas is created
Canvas.registerFont("comicsans.ttf", {family: "Comic Sans"});

var canvas = new Canvas(500, 500),
  ctx = canvas.getContext("2d");

ctx.font = "12px "Comic Sans"";
ctx.fillText(250, 10, "Everyone hates this font :(");

不过可能会发现Canvas.registerFont is not a function这是因为npm版本的没有这个函数。

所以你需要去找另一个github版https://github.com/chearon/node-canvas#12971f64a66b

git clone 下来

然后将Canvas = require("canvas")改成require("./node-canvas")，
将var canvas = new Canvas(300, 200)改成var canvas = new Canvas.Canvas(300, 200)

如果遇到这个问题，请cd进你的node-canvas目录执行npm install
如果还是不行，请执行npm install -g node-gyp

然后再cd项目目录执行node-gyp rebuild，then cd 进node-canvas同样执行node-gyp rebuild

如果成功则会出现

.
├── 1.html
├── composer.json
├── font
├── fz.ttf
├── img
├── index.js
├── node-canvas
├── node_modules
├── package.json
└── package-lock.json

var fs = require("fs"),path = require("path");
var http = require("http"),url = require("url");
var Canvas = require("./node-canvas"),Image = Canvas.Image;
var Fonts = [];
var filePath = path.resolve("./font");

let promise = new Promise(function(resolve, reject) {
  let i=0;
  fs.readdir(filePath,function(err,files){  
    if(err){  
      console.warn(err)  
    }else{
      files.forEach(function(filename){
        Canvas.registerFont(filePath + "/" + filename, {family: "font" + i});
        console.log(i);
        i++;
      });
    }
  });
  
});

promise.then(function() {
  console.log("ASDF");
  Fonts.forEach((Element) =>{
    console.log(Element);
  });
});

console.log("Hi!");


http.createServer(function (req, res) {
  var params = url.parse(req.url, true).query;
  var str = params.str + "
",site = params.site;
  var row =  1,col = 15,width = 1500;
  row = str.length / 15 + 1;
  var fontsize = width/col;
  var height = fontsize * row + 200;
  if(height < 1000){height = 1000}
  var canvas = new Canvas.Canvas(width, height), ctx = canvas.getContext("2d")
  res.writeHead(200,{"Content-Type": "image/png"});
  ctx.fillStyle = "#FFF";
  ctx.fillRect(0,0,canvas.width, canvas.height);
  ctx.fillStyle = "#000";
  if(row < 2){
    let num = str.length
    fontsize = 1200 / num;
    ctx.font = fontsize + "px "font"+ site +""";
    ctx.fillText(str,( width - num * fontsize ) / 2, (height-fontsize)/2 -200 + fontsize);
  }
  else{
    ctx.font = fontsize + "px "font"+ site +""";
    for(let i = 0;i < row ; i++){
      ctx.fillText(str.substring(i*15,(i+1)*15), 0, fontsize*(i+1));
    }
  }
  
  fs.readFile(__dirname + "/img/brand.png", function(err, squid){
    if (err) throw err;
    img = new Image;
    img.src = squid;
    ctx.fillStyle = "#42b983";
    ctx.fillRect(0,canvas.height - 230,canvas.width, 230);
    ctx.drawImage(img, canvas.width - img.width / 2 - 50, canvas.height - img.height / 2 - 50, img.width / 2, img.height / 2);
    res.end(canvas.toBuffer());
  });
}).listen(8080);