public with sharing class ResizeImageController 
{
     public Attachment theAttachment{get;set;}
     public Attachment thumbnail{get;set;}
     public String resizedBase64Value{get;set;}
     public ResizeImageController()
     {
            thumbnail = new Attachment();
            theAttachment = new Attachment();
         }
     
    public String theBase64Value
    {
          get
          {
            if(theAttachment.Body != null)
            {
                theBase64Value = EncodingUtil.base64Encode(theAttachment.Body);
                theAttachment.Body = null;//null out as we don't need this any more.helps to reduce view state
            }
            return theBase64Value;
          }
          set;
    }
     
     public void doAction()
     {
        //doesn't do any thing but the uploaded image is put in the view state
     }
         //code to save the resized image
     
     public void saveThumbNail()
     {
        //create any object to save the attachment to
        Merchandise__c theMerchandise = new Merchandise__c(); //custom object to attach the attachment to

        theMerchandise.Name = 'test merchandise'+DateTime.now();
        theMerchandise.Description__c = 'test merchandise';
        theMerchandise.Price__c = 55;
        theMerchandise.Total_Inventory__c = 5;
        insert theMerchandise;

        thumbnail.ParentId = theMerchandise.Id;
        thumbnail.Name = theAttachment.Name;
        String tempvalue =  resizedBase64Value.substringAfterLast('base64,');//apex doesn't seem to like this MIME type info .so,removing that part.
        thumbnail.Body = EncodingUtil.base64Decode(tempvalue);
        insert thumbnail;
     }
     
}