<!DOCTYPE html> <html> <head> <meta charset="UTF-8"> <title></title> <script src="https://cdn.bootcss.com/jquery/3.2.1/jquery.min.js"></script> </head> <body> <input type="file" id="picFile" onchange="readFile(this)"/> <img style="" id="img" src="" /> <script> function readFile(obj){ var file = obj.files[0]; //判断类型是不是图片 if(!/image\/\w+/.test(file.type)){ alert("请确保文件为图像类型"); return false; } var reader = new FileReader(); reader.readAsDataURL(file); reader.onload = function(e){ dealImage(this.result,{width:200},function(base){ document.getElementById(‘img‘).setAttribute(‘src‘,base) }); } } /** * 图片压缩，默认同比例压缩 * @param {Object} path * pc端传入的路径可以为相对路径，但是在移动端上必须传入的路径是照相图片储存的绝对路径 * @param {Object} obj * obj 对象 有 width， height， quality(0-1) * @param {Object} callback * 回调函数有一个参数，base64的字符串数据 */ function dealImage(path, obj, callback){ var img = new Image(); img.src = path; img.onload = function(){ var that = this; // 默认按比例压缩 var w = that.width, h = that.height, scale = w / h; w = obj.width || w; h = obj.height || (w / scale); var quality = 0.7; // 默认图片质量为0.7 //生成canvas var canvas = document.createElement(‘canvas‘); var ctx = canvas.getContext(‘2d‘); // 创建属性节点 var anw = document.createAttribute("width"); anw.nodeValue = w; var anh = document.createAttribute("height"); anh.nodeValue = h; canvas.setAttributeNode(anw); canvas.setAttributeNode(anh); ctx.drawImage(that, 0, 0, w, h); // 图像质量 if(obj.quality && obj.quality <= 1 && obj.quality > 0){ quality = obj.quality; } // quality值越小，所绘制出的图像越模糊 var base64 = canvas.toDataURL(‘image/jpeg‘, quality ); // 回调函数返回base64的值 callback(base64); } } </script> </body> </html>