How to validate the file name in Laravel 5.4

I have a form with three input fields. I want to validate the input value before processing them. Where I want to validate the file name before processing it. I use regular expression and alpha_dash. But I got an error for a valid file name. I want my file name only to contain small letter, numbers, underscore and dashes. How can I check the validation of the file name for my file?

Html

 <form action="create" method="POST"  enctype="multipart/form-data">
          
      <table cellpadding="2" width="20%"  align="center"
         cellspacing="2">

         <tr>
           <td colspan=2>
           <center><font size=4><b>Add the iteams  please</b></font></center>
           </td>
         </tr>

         <tr>
           <td>Heading</td>
           <td><input type="text" name="heading" id="heading" size="30">
           {!! $errors->first('heading', '<p class="red">:message</p>') !!}
           </td>
         </tr>

         <tr>
           <td>Image</td>
           <td><input type="file" name="image" id="image" size="40">
           {!! $errors->first('image', '<p class="red">:message</p>') !!}
           </td>
         </tr>

         <tr>
           <td></td>
           <td colspan="2"><input type="submit" name="submit" value="Add Item" /></td>
         </tr>
     </table>
 </form>

controller part

1. Using Regular expression format:

- I got error message, “ The image format is invalid” .

 public function store(){
    $this->validate(request(),[
          'heading'=>'required',
          'contentbody'=>'required',
           ‘image'=>['required','image','mimes:jpeg,png,jpg,gif,svg','max:2048','http://regex:/^[a-z0-9-_]+$/' ]

        ]);

}

2. using Alpa_dash:

- I got error message, “The image may only contain letters, numbers, and dashes” .

public function store(){
 $this->validate(request(),[
           'heading'=>'required',
          'contentbody'=>'required',
          'image'=>'required|image|mimes:jpg,png,jpeg,gif,svg|max:2048|alpha_dash'
}

Please help, Thank you!

via Chebli Mohamed