XML Publisher - Display BLOB Image Dynamically

hi

i need create XML (RTF) report that showing all employees and signatures, and i have table contains the employee numbers and BLOB column, and these my steps to create a new report but not working with me

1- create a new function

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CREATE OR REPLACE FUNCTION xx_getbase64( p_source BLOB )

RETURN CLOB

IS

v_result CLOB;

BEGIN

DBMS_LOB.createtemporary(lob_loc => v_result, CACHE => FALSE, dur => 0);

Wf_Mail_Util.EncodeBLOB ( p_source, v_result);

RETURN ( v_result );

END xx_getbase64;

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2- create a new rdf with this query

SELECT

CUSTOMER_NUMBER,

DOC_ID,

DOC_NAME,