<img src="images/m1.png" id="img1">

<form action="" method="post">

<input type="file" name="file1" id="file1" accept="image/*" capture="camera" onchange=showit();">

<button type="submit">上传</button>

</form>

<script type="text/javascript">

  function showit(){

    var fr=new FileReader();

    fr.readAsDataURL(document.getElementById("file1").files[0]);

    fr.onload=function(){

      document.getElementById("img1").src=this.result;

    }

  }

</script>