Is it possible to resize a blob image? I've got a table with an image blob field in it, which stores jpg files.

As those jpg files are shown in a web page, I would like to resize them in order to spend less bandwidth when my web page call them.

First, I thought I could resize a jpg file, stored in blob field, when doing a select statement and using command ORDimage.process. But it seems it's not possible.

CREATE OR REPLACE FUNCTION ORGPOLV2.resize_img (i_cod_op INTEGER)
      RETURN blob
   IS
      v_photo     blob ;
   BEGIN

     select img_simbolo_op
      into v_photo
      from tbl_op
      where cod_op=i_cod_op for update;

     ordimage.process(v_photo, 'maxScale=32 32');

 update tbl_op set img_simbolo_op = v_photo where cod_op=0;
--
commit;

    select img_simbolo_op
    into v_photo
    from tbl_op
    where cod_op=0;


      RETURN v_photo;
   END resize_img;
/


With this function, I got error:

ORA-14551: cannot perform a DML operation inside a query 
ORA-06512: at "RESIZE_IMG", line 10


My question is: Is it possible to resize a jpg file in a blob field?

Maybe my approach with ordimage.process is wrong and there is another way.
Try this:

CREATE OR REPLACE FUNCTION resize_img (i_ID INTEGER)
   RETURN BLOB
IS
   vImageData     BLOB;
   vSizedImage BLOB;

BEGIN

  SELECT img_simbolo_op
         INTO vImageData
         FROM tbl_yourtable
        WHERE my_ID = i_ID; 

  DBMS_Lob.createTemporary(vSizedImage, FALSE, DBMS_LOB.CALL);

  ORDSYS.OrdImage.processCopy(vImageData, 'maxScale=75 75', vSizedImage);


  return vSizedImage;

END resize_img;