Finding Image Type for a file

This is a follow up on my previous post on URLConnection APIs
We will use this API to find out the image type of a given file. Here is the udf.

<cffunction name="getMimeType">
    <cfargument name="filepath">

    <cfset var urlConn = createObject("java", "java.net.URLConnection")>
    <cfset var fileobj = fileopen(filepath, "readbinary")>
    <!--- just read the first 20 characters of the file as thats sufficient --->

    <cfset var bytes = fileread(fileobj, 20)>
    <cfset var istream = createObject("java", "java.io.ByteArrayInputStream").init(bytes)>
    <cfset fileobj.close()>
    <cfreturn urlConn.guessContentTypeFromStream(istream)>
</cffunction>

<cffunction name="GetImageType">
    <cfargument name="filepath">
    <cfset var mimetype = getMimeType(filepath)>
    <cfset var imagetype="">
    <cfif not isDefined("mimetype")>
        <cfthrow message="Not an Image file">
    </cfif>
    <cfswitch expression="#mimetype#">
        <cfcase Value="image/gif">
            <cfset imagetype="gif">
        </cfcase>
        <cfcase Value="image/x-bitmap">
            <cfset imagetype="bmp">
        </cfcase>
        <cfcase Value="image/png">
            <cfset imagetype="png">
        </cfcase>
        <cfcase Value="image/jpeg">
            <cfset imagetype="jpeg">
        </cfcase>
        <cfcase Value="image/jpg">
            <cfset imagetype="jpeg">
        </cfcase>
        <cfdefaultcase>
            <cfthrow message="Not an Image file">
        </cfdefaultcase>
    </cfswitch>
    <cfreturn imagetype>
</cffunction>

If I run the code below

<cfset filepath = "C:\temp\test.jpg">
<cfoutput>#GetImageType(filepath)#</cfoutput>

It nicely prints out "jpeg".

You should note that I used the new File IO function added in ColdFusion 8 using which I can read as many no of bytes from the file as I want. No more reading the entire file into memory.

More extensive post on File IO functions coming next !