教程|教你如何给你的头像添加一个好看的国旗

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", {
		 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({
		 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.git

演示地址：http://alterem.gitee.io/avatar/