var objFile = document.getElementById("img_data");
	var formData = new FormData(objFile);
    $.ajax({ 
          url: 'http://localhost:8080/big/gogo?type=save_img',
          type: "post",
          data: formData, 
          cache: false,  
          contentType: false,
          processData: false
      });

作用对象

<input type="file" name="head" id="test" value="上传图片">

当然 img 标签也一样