最近看到微博头像上传功能很感兴趣，于是就使用canvas写了一个，本文写的不好还请见谅。本程序目前在谷歌浏览器和火狐浏览器测试可用，ie浏览器无法支持。
因为ie的安全机制不允许img使用本地路径，所以若想ie支持本程序，必须先将图片上传，然后给img对象上传后的图片地址。
我在这里没写，是因为暂时没写上传功能的后端代码,并且还不确定有没有更好的解决办法。
如下是新浪的
如下是我做的截取部分
代码：
var canvas = document.getElementById('canvas'),
context = canvas.getContext('d'),
canvas = document.getElementById('canvas_dp'),
context = canvas.getContext('d'),
image = new Image(),//document.getElementById('myimg'),
imageData,
scale,//缩放比例
rubberbandRectangle = {left:,top:,width:,height:},
resize = ;
oldRubberbandRectangle = {};
dragging = false,
extending = false,
mousedown = {};
// Functions.....................................................
function windowToCanvas(canvas, x, y) {
var canvasRectangle = canvas.getBoundingClientRect();
return {
x: x - canvasRectangle.left,
y: y - canvasRectangle.top
};
}
//将截取的图片画在小的canvas中
function captureCanvasPixels() {
context.drawImage(image,rubberbandRectangle.left/scale,rubberbandRectangle.top/scale,rubberbandRectangle.width/scale,rubberbandRectangle.height/scale,,,,);
}
function drawRubberband() {
context.save();
context.beginPath();//开始新的路径
rect(rubberbandRectangle.left,
rubberbandRectangle.top,
rubberbandRectangle.width,
rubberbandRectangle.height);
context.fillStyle='rgba(,,,.)';
addRectanglePath();
context.fill();//填充路径
context.fillStyle='rgba(,,,)';
captureCanvasPixels();//将选取的图像copy到预览canvas中
context.beginPath();
context.strokeStyle = '#';
context.lineWidth = .;
context.arc(rubberbandRectangle.left+rubberbandRectangle.width,rubberbandRectangle.top+rubberbandRectangle.height,,,Math.PI*,true);
context.fill();//填充路径
context.stroke();//填充路径
context.restore();
}
function rect(x, y, w, h, direction){
if(direction){//逆时针
context.moveTo(x, y);
context.lineTo(x, y + h);
context.lineTo(x + w, y + h);
context.lineTo(x + w, y);
}else{//顺时针
context.moveTo(x, y);
context.lineTo(x + w, y);
context.lineTo(x + w, y + h);
context.lineTo(x, y + h);
}
context.closePath();
}
function addRectanglePath(){
rect(,,canvas.width,canvas.height,true);
}
function startDragging(loc){
mousedown.x = loc.x;
mousedown.y = loc.y;
oldRubberbandRectangle.left = rubberbandRectangle.left;
oldRubberbandRectangle.top = rubberbandRectangle.top;
}
function updateRubberbandRectangle(loc){
var left = oldRubberbandRectangle.left + loc.x-mousedown.x;
var top = oldRubberbandRectangle.top + loc.y - mousedown.y;
rubberbandRectangle.left = (left<) "htmlcode">
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-">
<title>CarlZhang</title>
</head>
<body>
<div name="container" style="height:px;width:px;border:#BB px solid;text-align:center">
<canvas id="canvas" style="z-index: ; " height="" width=""></canvas>
</div>
<!--预览-->
<div name="display" style="height:px;width:px;border:#BB px solid;position:absolute;left:px;top:px;">
<canvas id="canvas_dp" style="z-index: ; " height="" width=""></canvas>
</div>
<!--上传-->
<input id="myfileInput" type="file" accept="image/gif, image/jpeg, image/x-png"/>
<script src="/UploadFiles/2021-04-02/cavas_img_upload.js">
以上代码很简单吧，附有注释，有不同见解的朋友，欢迎给我留言，共同交流学习进步。欲了解更多有关canvas头像截取上传问题，请持续关注本站，本站每天都有新的内容更新。