Digital Image Metadata and Exif files - Forensics Research Paper

Digital Image Metadata and Exif files - Forensics - Research Paper Example (University of Reading, 2011) Data of raster images are represented in the form of a pixel which is the smallest part of a display screen. Each pixel represents the colour and its intensity. Raster is a display space of x and y grid for two dimension image and x, y and z coordinate for three dimension images. The raster images are difficult to modify without loosing any information as they are mapped directly to the raster space. The size of raster image files is usually far more than the size of vector image files. The most common types of raster images files include BMP, GIF, TIFF, JPEG and PNG. (Whatis.com?, 1997) Tagged Image File Format (TIFF) type of digital images contains complete information about the images and no data is lost when saved. It is generally referred as â€Å"lossless† format. Their sizes are too big to be suitable for delivery by web. (University of Reading, 2011) Joint Photographic Experts Group (JPEG) type of digital images compresses data when saved. It looses its data whenever any modification is done and therefore generally referred as â€Å"lossy† format. It is good for delivery of photographic images by web. (University of Reading, 2011) Graphical Interchange Format (GIF) type of digital images is used for icons and graphics having limited range of colours. It does not loose information when saved and therefore generally referred as â€Å"lossless† format. It is good only for some types of images and used mostly on internet. (University of Reading, 2011) Portable Network Graphics (PNG) type of digital images is added recently in graphics file types. It has better compression result and support true colours. It is high quality and small size digital image file. (University of Reading, 2011) Data of vector images on the other hand is represented by vector objects which are geometrical figures such as lines, circles, rectangles, curves and many more shapes of geometry. Scaling, transformation, resizing, and resha ping are accurately done on vector images as its data is based on mathematical instructions. The most common types of vector image files have extension of SVG. They are used in software that is dedicated towards drawing and illustration such as Adobe Flash, CorelDraw, Inkscape, ACD Canvas, etc. Figure 1 shows comparison between digital images of Raster and Vector types. (JISC Digital Media, 2009) Figure 1: Comparison of Raster Images and Vector Images (JISC Digital Media, 2009) Metadata Metadata is the digital information that describes structure and relationship amongst different contents of digital data files. Earlier databases stored metadata as headers of the actual data files. Metadata is stored in a separate database file generally referred as registry or repository. For example, Windows operating system have registry in which the structure of entire hardware, device drivers and actual data is stored. (Bargmeyer & Gillman) The simplest example of metadata is an index of a book which gives the name of the chapters in the book and page numbers where it is located. If an index is removed from the book, it becomes extremely difficult to find any chapter whenever some information is needed. Similarly, metadata helps in organizing, storing, processing, retrieving and displaying contents of a data file which is otherwise meaningless. Metadata adds meaning to a data file by interpreting its contents according to its context. Digital Image files did not have