图片转base64

   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>

相关文章