Commonly used Image and picture file formats
GIF-Graphic Interchange File:
GIF images are limited to 8 bits of color depth that is 2 powers 8 which equals 256 colors. This is a commercial image format developed by CompuServe information services, an online company once owned by Unisys and presently folded in to America Online. Time Warner incorporation in 1994, Unisys announced painted fee charge to all software developers who use the GIF format. GIF is preferred file format for monochrome grey scale images. The GIF compression method works, if the picture is a cartoon, line drawing, hand written text (or) X-ray which don’t have the richness of color and details of a color photographs. This format is preferred for transmitting pictures on the World Wide Web [www] as web applications and it is supported by all the web browsers. The picture quality is quite sufficient for VDUs [Visual Display Unit].
JPEG- Joint Photographic Expert Group:
It is a standard method of compressing photographic image. JPEG is the most common image format used by digital cameras and other photographic image captured devices. It is mostly used for storing and transmitting photographs on the World Wide Web. It may not suit for textual graphics or line drawing like images because its compression method performs badly on these types of images. This format is right format for those photo images which are very small in size and apt for websites and emails. A new JPEG-2000 file format is available now in many newer program versions with various file extensions normally .jp2. JPEG-2000 uses a wavelet compression method. It has a loss les option.
A Bit Map can be defined as a simple information matrix describing the individual dots on a computer screen (or) other display (or) printing device. These dots are nothing but the smallest element of resolution of the screen (or) printer. Each dot is called as a picture element (or) pixels (or) pels. For representing a black and white image (or) a monochrome image one dimensional matrix is used and the picture elements will be either ON (or) OFF i.e., 1 (or) 0 respectively. The picture elements can be represented by varying shades of colors. [4 bits= 16 colors, 8 bits= 256 colors, 16 bits = 65536 colors and 24 bits = millions of colors]. Bit Maps are used for photo realistic images and for complex drawings which require fine details. Vector drawn objects are used for lines, boxes, circles, polygons and other graphic shapes that can be filled with colors and patterns. These images/shapes can be mathematically expressed in angles. These images depend on the display resolution, computers, graphics hardware and monitor.