<div style="width:200px;height:200px;">
 <label for="ceshi" style="display:block;">
  <img style="width:200px;height:200px;" id="image" src=""/>
  <input id="ceshi" type="file" onchange="selectImage(this);" hidden/>
 </label>
</div>

 var image = '';
 function selectImage(file){
 if(!file.files || !file.files[0]){
   return;
 }
 var reader = new FileReader();
 reader.onload = function(evt){
  document.getElementById('image').src = evt.target.result;
  image = evt.target.result;
 }
 reader.readAsDataURL(file.files[0]);
 }
 function uploadImage(){
  console.log(image);
  $.ajax({
   type:'POST',
   url: 'ajax/uploadimage', //图片上传地址
   data: {image: image},
   async: true,
   dataType: 'json',
   success: function(data){
   if(data.success){
    alert('上传成功');
   }else{
   alert('上传失败');
   }
  },
  error: function(err){
   alert('网络故障');
  }
 });
}