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How to Check if File is Image Using PL/SQL?

In this blog post, I am sharing a function with which you can check if a file is an image file or not using PL/SQL. The program will check the file by reading its header not the extension name of the file. Currently, the function can identify three types of images which are JPG, PNG, and GIF.

PL/SQL Function to Check if File is an Image File

The following PL/SQL function will read the file header and then will return the image type in varchar2 data type. The function get_image_type takes two arguments, and they are as follows:

  1. Oracle Directory Object (as i_dir) Learn How to Create Oracle Directory Object.
  2. Filename (as i_file) file should exist in the directory.
CREATE OR REPLACE FUNCTION get_image_type (i_dir    IN VARCHAR2,
                                           i_file   IN VARCHAR2)
   RETURN VARCHAR2
AS
   l_bfile       BFILE;
   l_blob        BLOB;
   l_file_type   VARCHAR2 (50);
BEGIN
   DBMS_LOB.createtemporary (l_blob, FALSE);
   l_bfile := BFILENAME (i_dir, i_file);
   DBMS_LOB.fileopen (l_bfile, DBMS_LOB.file_readonly);
   DBMS_LOB.loadfromfile (l_blob, l_bfile, DBMS_LOB.getlength (l_bfile));
   DBMS_LOB.fileclose (l_bfile);

   IF RAWTOHEX (DBMS_LOB.SUBSTR (l_blob, 8, 1)) = '89504E470D0A1A0A'
   THEN
      l_file_type := 'PNG';
   ELSIF DBMS_LOB.SUBSTR (l_blob, 3, 1) = '474946'
   THEN
      l_file_type := 'GIF';
   ELSIF RAWTOHEX (DBMS_LOB.SUBSTR (l_blob, 3, 1)) = 'FFD8FF'
   THEN
      l_file_type := 'JPG';
   ELSE
      l_file_type := 'The file is not an image.';
   END IF;

   RETURN l_file_type;
EXCEPTION
   WHEN OTHERS
   THEN
      IF DBMS_LOB.fileisopen (l_bfile) = 1
      THEN
         DBMS_LOB.fileclose (l_bfile);
      END IF;

      DBMS_LOB.freetemporary (l_blob);
      RETURN 'The file does not exists.';
END get_image_type;

Test

In the below PL/SQL program, change the MY_FILES Oracle directory object with your directory object and change the file name with the file available in MY_FILES directory location.

SET SERVEROUTPUT ON;

DECLARE
   i_image_type   VARCHAR2 (50);
BEGIN
   i_image_type := get_image_type ('MY_FILES', 'oracle-logo-gif-to-use.gif');

   IF i_image_type IN ('JPG', 'GIF', 'PNG')
   THEN
      DBMS_OUTPUT.put_line ('The file is a valid ' || i_image_type || ' image.');
   ELSE
      DBMS_OUTPUT.put_line (i_image_type);
   END IF;
END;
/

Output

The file is a valid GIF image.
PL/SQL procedure successfully completed.

See also: