<div>
  <img class="copyright-img" id="activity_image"  src="" />
  <input type="file" name="file">
</div>

//上传活动图片
$("input[name='file']").live('change',function(e){
    var fileMsg = e.currentTarget.files;//获取图片元素
    console.log(fileMsg);
    var formData = new FormData();
    formData.append("file", fileMsg[0]);
    $.ajax({
        url:'user.php?c=unit_group&a=photo_upload', /*接口域名地址*/
        type:'post',
        data: formData,
        contentType: false,
        processData: false,
        success:function(res){
            console.log(res);
        }
    })
});