今天朋友圈又火了，听说原因是 @腾讯官网 就能得到一顶绿色的帽子，啊呸，是一个好看的国庆节头像，可是听说没一会就502了，那么我们自己动手实现一个吧

由于代码比较简单就不一一介绍了。

var cvs = document.getElementById("cvs");
var ctx = cvs.getContext("2d");
var exportImage = document.getElementById("export");
var img = document.getElementById("img");
var hat = "hat6";
var canvasFabric;
var hatInstance;
var screenWidth = window.screen.width < 500 ? window.screen.width : 300;

function viewer() {
  var file = document.getElementById("upload").files[0];
  console.log(file);
  var reader = new FileReader;
  if (file) {
    reader.readAsDataURL(file);
    reader.onload = function(e) {
      img.src = reader.result;
      img.onload = function() {
        img2Cvs(img)
      }
    }
  } else {
    img.src = ""
  }
}

function img2Cvs(img) {
  cvs.width = img.width;
  cvs.height = img.height;
  cvs.style.display = "block";
  canvasFabric = new fabric.Canvas("cvs",{
    width: screenWidth,height: screenWidth,backgroundImage: new fabric.Image(img,{
      scaleX: screenWidth / img.width,scaleY: screenWidth / img.height
    })
  });
  changeHat();
  document.getElementById("uploadContainer").style.display = "none";
  document.getElementById("uploadText").style.display = "none";
  document.getElementById("upload").style.display = "none";
  document.getElementById("change").style.display = "block";
  document.getElementById("exportBtn").style.display = "block";
  document.getElementById("tip").style.opacity = 1
}

function changeHat() {
  document.getElementById(hat).style.display = "none";
  var hats = document.getElementsByClassName("hide");
  hat = "hat" + (+hat.replace("hat","") + 1) % hats.length;
  var hatImage = document.getElementById(hat);
  hatImage.style.display = "block";
  if (hatInstance) {
    canvasFabric.remove(hatInstance)
  }
  hatInstance = new fabric.Image(hatImage,{
    top: 40,left: screenWidth / 3,scaleX: 100 / hatImage.width,scaleY: 100 / hatImage.height,cornerColor: "#0b3a42",cornerStrokeColor: "#fff",cornerStyle: "circle",transparentCorners: false,rotatingPointOffset: 30
  });
  hatInstance.setControlVisible("bl",false);
  hatInstance.setControlVisible("tr",false);
  hatInstance.setControlVisible("tl",false);
  hatInstance.setControlVisible("mr",false);
  hatInstance.setControlVisible("mt",false);
  canvasFabric.add(hatInstance)
}

function exportFunc() {
  document.getElementsByClassName("canvas-container")[0].style.display = "none";
  document.getElementById("exportBtn").style.display = "none";
  document.getElementById("tip").innerHTML = "长按图片保存或分享";
  document.getElementById("change").style.display = "none";
  cvs.style.display = "none";
  exportImage.style.display = "block";
  exportImage.src = canvasFabric.toDataURL({
    width: screenWidth,height: screenWidth
  })
}

最后效果

拖动图片可见已经拼合成一张完整图片了

右键查看源代码

所有图片素材均来自腾讯官网

源码地址：https://gitee.com/alterem/avatar

演示地址：http://alterem.gitee.io/avatar/

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