How to check the exact size of a picture file in a LONG RAW column of a table.

My HR System needs to insert a photo of each one of my employees in my table PESSOA_FISICA_FOTO in the LONG RAW column, the IM_PESSOA_FISICA:

Table TASY.PESSOA_FISICA_FOTO:

Name Null? Type

-------------------------- -------- ------------

CD_PESSOA_FISICA NOT NULL VARCHAR2(10)

IM_PESSOA_FISICA NOT NULL LONG RAW

...

This mentioned photo is a '.png' file, which its size can vary depends upon the size of the file, and store more or less disk space in my IM_PESSOA_FISICA table column.

I need to check the allocated disk space of each photo in each one of the rows in my table PESSOA_FISICA_FOTO, so I can have the exactly disk space allocated in my table,