function convertImgToBase64(url, callback, outputFormat){ var canvas = document.createElement('CANVAS'); var ctx = canvas.getContext('2d'); var img = new Image; img.crossOrigin = 'Anonymous'; img.onload = function(){ var width = img.width; var height = img.height; // 按比例压缩4倍 var rate = (width<height ? width/height : height/width)/4; canvas.width = width*rate; canvas.height = height*rate; ctx.drawImage(img,0,0,width,height,0,0,width*rate,height*rate); var dataURL = canvas.toDataURL(outputFormat || 'image/png'); callback.call(this, dataURL); canvas = null; }; img.src = url; } convertImgToBase64("http://img3.imgtn.bdimg.com/it/u=4271053251,2424464488&fm=21&gp=0.jpg", function(base64Img){ // base64Img为转好的base64,放在img src直接前台展示(<img src="data:image/jpg;base64,/9j/4QMZRXh...." />) console.log(base64Img); // base64转图片不需要base64的前缀data:image/jpg;base64 } )
转本地 图片 base64
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title>简单的html5 File测试 for pic2base64 本地图片</title> <style> </style> <script> window.onload = function(){ var input = document.getElementById("demo_input"); var result= document.getElementById("result"); var img_area = document.getElementById("img_area"); if ( typeof(FileReader) === 'undefined' ){ result.innerHTML = "抱歉，你的浏览器不支持 FileReader，请使用现代浏览器操作！"; input.setAttribute( 'disabled','disabled' ); } else { input.addEventListener( 'change',readFile,false );} } function readFile(){ var file = this.files[0]; //这里我们判断下类型如果不是图片就返回 去掉就可以上传任意文件 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); //转化为base64位 reader.onload = function(e){ result.innerHTML = '<img src="'+this.result+'" alt=""/>'; img_area.innerHTML = '<div class="sitetip">图片img标签展示：</div><img src="'+this.result+'" alt=""/>'; } } </script> </head> <body> <input type="file" value="sdgsdg" id="demo_input" /> <textarea id="result" rows=30 cols=300></textarea> <p id="img_area"></p> </body> </html>