ขอการทำ Capchar ของ ASP หน่อยคร้าฟป๋ม หรือไม่ถ้าผมต้องารใส่รูปต้องทำอย่างไรจาก โค๊ดอันนี้

<style>
#captcha
{
height:30px;
background-image:url(image/1.jpg);
background-repeat:no-repeat;
font-size:22px;
position:relative;
}
#captcha_gen
{
left:10px;
top:3px;
position:absolute;
Font-family:Monospace;
font-weight:bold;
text-align:justify;
}
</style>

<div id="captcha">
<div id="captcha_gen">
      <span id="txtCaptchaDiv" style="color:#013ADF"></span>
      <input type="hidden" id="txtCaptcha" />
                </div>

<input name="txtInput" type="text" id="txtInput" size="30" maxlength="7" />

<script type="text/javascript">
	function checkform(theform){
		var why = "";
		if(theform.txtInput.value == ""){
			why += "กรุณาใส่รหัสยืนยันตัวตน.\n";
		}
		if(theform.txtInput.value != ""){
			if(ValidCaptcha(theform.txtInput.value) == false){
				why += "คุณใส่รหัสยืนยันตัวตนผิดพลาด.\n";
				why += "หรือ คุณกรอกข้อมูลไม่ครบถ้วน.\n";
			}
		}
		if(why != ""){
			alert(why);
			return false;
		}
	}
 
	var a = Math.ceil(Math.random() * 9)+ '';
	var b = Math.ceil(Math.random() * 9)+ '';       
	var c = Math.ceil(Math.random() * 9)+ '';  
	var d = Math.ceil(Math.random() * 9)+ '';  
	var e = Math.ceil(Math.random() * 9)+ '';  
	var f = Math.ceil(Math.random() * 9)+ '';
	var g = Math.ceil(Math.random() * 9)+ '';
	  
	var code = a + b + c + d + e+f+g;
	document.getElementById("txtCaptcha").value = code;
	document.getElementById("txtCaptchaDiv").innerHTML = code;	

function ValidCaptcha(){
	var str1 = removeSpaces(document.getElementById('txtCaptcha').value);
	var str2 = removeSpaces(document.getElementById('txtInput').value);
	if(document.form1.subject.value=="") {
		document.form1.subject.focus() ;
		return false ;
		}else if(document.form1.detail.value=="") {
		document.form1.detail.focus() ;
		return false ;
		return true;	
		}else{
		  submitForm();
		}
	if (str1 == str2){
		alert('Save Complete'); 
		
	}else{
		return false;
	}
}
function removeSpaces(string){
	return string.split(' ').join('');
}
</script>