5 Working with Metadata in Images

5.4.1 EXIF

The Exchangeable Image File Format (EXIF) is the standard for image file storage for digital still cameras. It was developed by the Japan Electronic Industry Development Association (JEIDA) as a standard way of storing images created by digital cameras as well as metadata about the images. EXIF image metadata can be stored in TIFF and JPEG format images. interMedia supports the extraction of EXIF metadata from TIFF and JPEG file formats.

5.4.2 IPTC–IIM

The International Press Telecommunications Council-Information Interchange Model (IPTC-IIM) Version 4 is a standard developed jointly by the International Press Telecommunications Council and the Newspaper Association of America. This metadata standard is designed to capture information that is important to the activities of news gathering, reporting, and publishing. These information records are commonly referred to as IPTC tags.

The use of embedded IPTC tags in image file formats became widespread with the use of the Adobe Photoshop tool for image editing. IPTC metadata can be stored in TIFF and JPEG format images. interMedia supports the extraction of IPTC metadata from TIFF and JPEG file formats.

5.4.3 XMP

The Extensible Metadata Platform (XMP) is a standard metadata format, developed by Adobe, for the creation, processing, and interchange of metadata in a variety of applications. XMP uses Resource Description Framework (RDF) technology for data modeling. XMP also defines how the data model is serialized (converted to a byte stream), and embedded within an image file. interMedia supports the extraction of XMP metadata from GIF, TIFF, and JPEG file formats. interMedia also supports writing XMP data packets into GIF, TIFF, and JPEG file formats.

For more information about XMP, see the Adobe Systems Incorporated Web site at

http://www.adobe.com/

For more information about RDF, see the Resource Description Framework Web page on the World Wide Web Consortium Web site at

http://www.w3.org/RDF/

5.6.1 Creating a Table for Metadata Storage

Before you can extract or embed metadata, you must create the table and columns where the metadata will be stored. The following PL/SQL code segment creates the photos table with four XMLTYPE columns (metaORDImage, metaEXIF, metaIPTC, and metaXMP) to store each type of image metadata, and two ORDIMAGE columns (image and thumb) for the original image and the thumbnail image, respectively. Each metadata column is bound to its corresponding metadata schema. For example, the metaEXIF column is bound to the XML schema stored at http://xmlns.oracle.com/ord/meta/exif, and is defined as the XML element exifMetadata.

For ease of reference, the code statements where the image metadata columns are defined and bound to XML schemas are highlighted in bold.

--
-- Create the PHOTOS table
--
CREATE TABLE photos( id           NUMBER PRIMARY KEY,
                     description  VARCHAR2(40) NOT NULL,
                     metaORDImage XMLTYPE,
                     metaEXIF     XMLTYPE,
                     metaIPTC     XMLTYPE,
                     metaXMP      XMLTYPE,
                     image        ORDSYS.ORDIMAGE,
                     thumb        ORDSYS.ORDIMAGE )
LOB(image.source.localdata)  -- storage images with 32K chunk
  STORE AS (chunk 32k)
LOB(thumb.source.localdata)  -- but the thumbnails with only 16k
  STORE AS (chunk 16k)
-- and bind the XMLType columns to the interMedia metadata schemas
XMLType COLUMN metaORDImage
  XMLSCHEMA "http://xmlns.oracle.com/ord/meta/ordimage"
  ELEMENT "ordImageAttributes"
XMLType COLUMN metaEXIF
  XMLSCHEMA "http://xmlns.oracle.com/ord/meta/exif"
  ELEMENT "exifMetadata"
XMLType COLUMN metaIPTC
  XMLSCHEMA "http://xmlns.oracle.com/ord/meta/iptc"
  ELEMENT "iptcMetadata"
XMLType COLUMN metaXMP
  XMLSCHEMA "http://xmlns.oracle.com/ord/meta/xmp"
  ELEMENT "xmpMetadata";

5.6.2 Extracting Image Metadata

The following PL/SQL procedure extracts metadata from an image and stores it in the specified columns in the photos table you created. This procedure demonstrates the getMetadata( ) method, which returns an array of XML documents. The root element of each document is examined to determine the metadata type. The UPDATE statement stores the documents in the corresponding columns in the photos table.

For ease of reference, the code statement where the getMetadata( ) method is called is highlighted in bold.

--
-- fetch the metadata and sort the results
--
PROCEDURE extractMetadata(inID IN INTEGER)
IS
  img ORDSYS.ORDIMAGE;
  metav XMLSequenceType;
  meta_root VARCHAR2(40);
  xmlORD XMLType;
  xmlXMP XMLType;
  xmlEXIF XMLType;
  xmlIPTC XMLType;
 
BEGIN
 
-- select the image
SELECT image
INTO img
FROM PHOTOS
WHERE id = inID;

-- extract all the metadata
metav := image.getMetadata( 'ALL' );
 
-- process the result array to discover what types of metadata were
returned
FOR i IN 1..metav.count() LOOP
  meta_root := metav(i).getRootElement();
  CASE meta_root
    WHEN 'ordImageAttributes' THEN xmlORD := metav(i);
    WHEN 'xmpMetadata' THEN xmlXMP := metav(i);
    WHEN 'iptcMetadata' THEN xmlIPTC := metav(i);
    WHEN 'exifMetadata' THEN xmlEXIF := metav(i);
    ELSE NULL;
  END CASE;
END LOOP;

-- Update metadata columns
--
UPDATE photos
SET metaORDImage = xmlORD,
    metaEXIF = xmlEXIF,
    metaIPTC = xmlIPTC,
    metaXMP = xmlXMP
WHERE id = inID;
 
END extractMetadata;

5.6.3 Embedding Image Metadata

The following PL/SQL procedure demonstrates the putMetadata( ) method. This procedure accepts six arguments. The entry_id argument identifies the image in the photos table to be updated. The remaining arguments (title, creator, date, description, and copyright) are strings that will be formatted into an XMP packet and embedded within the target image.

This example creates an XML document instance based on the interMedia XML schema for XMP metadata. (This schema is preregistered with Oracle XML DB. See Oracle XML DB Developer's Guide for more information.) The schema for XMP metadata defines a single, global element <xmpMetadata>. The <xmpMetadata> element contains a single, well-formed RDF document. The RDF document contains a single <RDF> element, which is derived from the rdf namespace. This RDF document is constructed using elements defined by the Dublin Core Schema.

The call to the putMetadata( ) method embeds the metadata document into the image file. The UPDATE statement stores the new image and the new metadata back in the photos table.

For ease of reference, the code statement where the putMetadata( ) method is called is highlighted in bold.

--
-- write the metadata to the image
--
PROCEDURE write_metadata( entry_id IN VARCHAR2,
                          title IN VARCHAR2,
                          creator IN VARCHAR2,
                          date IN VARCHAR2,
                          description IN VARCHAR2,
                          copyright IN VARCHAR2 )
IS
  img ORDSYS.ORDImage;
  xmp XMLType;
  buf VARCHAR2(5000);
BEGIN
-- select the image
SELECT image
INTO img
FROM PHOTOS
WHERE id = entry_id FOR UPDATE;

-- Create the XMP packet it must be schema valid
-- to "http://xmlns.oracle.com/ord/meta/xmp"
-- and contain an <RDF> element. This example uses
-- the Dublin Core schema.

/* An example XML instance document
 
<xmpMetadata xmlns="http://xmlns.oracle.com/ord/meta/xmp" 
              xsi:schemaLocation="http://xmlns.oracle.com/ord/meta/xmp 
              http://xmlns.oracle.com/ord/meta/xmp" 
              xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
 
  <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
    <rdf:Description about="" xmlns:dc="http://purl.org/dc/elements/1.1/">
      <dc:title>A Winter Day<dc:title>
      <dc:creator>Frosty S. Man</dc:creator>
      <dc:date>21-Dec-2004</dc:date>
      <dc:description>a sleigh ride</dc:description>
      <dc:copyright>North Pole Inc.</dc:copyright>
    </rdf:Description>
  </rdf:RDF>
</xmpMetadata>
 
*/
 
buf := '<xmpMetadata xmlns="http://xmlns.oracle.com/ord/meta/xmp"
         xsi:schemaLocation="http://xmlns.oracle.com/ord/meta/xmp
         http://xmlns.oracle.com/ord/meta/xmp"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" >
  <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
  <rdf:Description about="" xmlns:dc="http://purl.org/dc/elements/1.1/">';
 
IF title IS NOT NULL THEN
  buf := buf || '<dc:title>' || htf.escape_sc(title) || '</dc:title>';
END IF;
 
IF creator IS NOT NULL THEN
  buf := buf || '<dc:creator>' || htf.escape_sc(creator)
             || '</dc:creator>';
END IF;
IF date IS NOT NULL THEN
  buf := buf || '<dc:date>' || htf.escape_sc(date)
             || '</dc:date>';
END IF;
IF description IS NOT NULL THEN
  buf := buf || '<dc:description>' || htf.escape_sc(description)
             || '</dc:description>';
END IF;
IF copyright IS NOT NULL THEN
  buf := buf || '<dc:copyright>' || htf.escape_sc(copyright)
             || '</dc:copyright>';
END IF;
 
buf := buf || '
  </rdf:Description>
  </rdf:RDF>
  </xmpMetadata>';

-- create the XML document
xmp := XMLType.createXML(buf, 'http://xmlns.oracle.com/ord/meta/xmp');
 
-- write the metadata
img.putMetadata( xmp, 'XMP' );
 
-- update the image
UPDATE photos
SET image = img,
    metaXMP = xmp
WHERE id = entry_id;
 
END write_Metadata;

5.10.1 Creating a Table for DICOM Metadata Storage

Before you can extract DICOM metadata, you must create the table and column where the metadata will be stored. The following PL/SQL code segment creates the medicalImages table with one XMLTYPE column (metadata) to store the DICOM image metadata, and two ORDIMAGE columns (image and thumb) for the original image and the thumbnail image, respectively. The metadata column is bound to the XML schema stored at http://xmlns.oracle.com/ord/meta/dicomImage, and is defined as the XML element DICOM_IMAGE.

For ease of reference, the code statements where the image metadata column is defined and bound to the XML schema are highlighted in bold.

create table medicalImages(id number primary key, 
                           description VARCHAR2(40),
                           metadata XMLType,
                           image ORDSYS.ORDIMAGE,
                           thumb ORDSYS.ORDIMAGE)
LOB (image.source.localdata) -- store images with 32K chunk
  STORE AS (chunk 32K)
LOB (thumb.source.localdata) -- but the thumbnails with only 16K
  STORE AS (chunk 16K)
-- and bind the XMLType columns to the interMedia metadata columns
XMLType column metadata
  XMLSCHEMA "http://xmlns.oracle.com/ord/meta/dicomImage"
  ELEMENT "DICOM_IMAGE";

5.10.2 Extracting DICOM Image Metadata

The following PL/SQL procedure extracts DICOM metadata from an image and stores it in the specified column in the medicalImages table you created. This procedure demonstrates the getDicomMetadata( ) method, which returns an XML document. The UPDATE statement stores the document in the corresponding column in the medicalImages table.

For ease of reference, the code statement where the getDicomMetadata( ) method is called is highlighted in bold.

--
PROCEDURE extractDicomMetadata(inID INTEGER)
IS
   local_image ORDSYS.ORDIMAGE;
   local_id INTEGER;
   dicom_metadata XMLType := NULL;
BEGIN 
   SELECT image INTO local_image FROM medicalImages WHERE id = inID;
   -- extract DICOM metadata
   dicom_metadata := local_image.getDicomMetadata('imageGeneral');
   IF (dicom_metadata IS NULL) THEN
      DBMS_OUTPUT.PUT_LINE('metadata is NULL');
   ELSE
      UPDATE medicalImages SET metadata = dicom_metadata where id = inID;
   END IF;
   -- let us print the namespace of the XML document containing the
   -- dicom metadata that we just extracted
   DBMS_OUTPUT.PUT_LINE('namespace: ' || dicom_metadata.getNamespace());
 
END extractDicomMetadata;
--