An Indexing and Querying System for Online Images Based on the PNG Format and Embedded Metadata
Jane Hunter, Zhimin Zhan · 1999
In this paper we describe an indexing, querying and browsing system for online images based on the PNG (Portable Network Graphics) image format and its ability to embed structured metadata within the image. First we describe a Java application which enables the computer-assisted generation and editing of Dublin Core-based metadata descriptions for digital images and the annotation of regions within images. This application integrates an image display window with a graphical user interface and metadata input forms generated from a hierarchical Resource Description Framework (RDF) schema. The schema definition is also used to validate the input descriptions and control the format of the output. At "Save " time, the image is converted from GIF or JPEG to PNG format and the validated metadata which has been input is embedded within the image. Secondly we describe an image-capable search engine developed through a simple code extension to DSTC's existing HotMeta web-page search engine. HotMeta crawls across the WWW extracting metatags from web pages and storing them in an indexed repository to enable searching. A simple code extension to HotMeta has enabled image search capabilities. Whenever HotMeta encounters a PNG image, it opens the image, extracts the metadata and saves this in the indexed repository. Finally we describe an improved image browsing method which exploits the metadata embedded in thumbnail PNG images.