Digitized Image and Graphics
A photograph is an analog representation of an image. It is continuous across its surface, with shades of one color blending into another.
Pixels: individual dots used to represent a picture(stands for picture elements).
Resolution: the number of pixels used to represent a picture
Two techniques to represent images
Raster-graphics format: store image information pixel by pixel.
Popular file formats: bitmap (BMP), GIF, and JPEG
Vector-graphics format: describes an image in terms of lines and geometric shapes.
Be not good for representing real-world images.
Be good for line art and cartoon-style drawings.
The most popular vector format used on the Web: Flash, SVG (Scalable Vector Graphics)
A bitmap file (BMP) supports 24-bit TrueColor.
File size is large.
May be compressed using run-length encoding.
The GIF format (Graphics Interchange Format)
Developed by CompuServe in 1987
Pronounced “Giff” by some and “Jiff” by others
Uses indexed color exclusively to reduce file size, which limits the number of available colors to 256.
Lossy compression
JPEG format (pronounced “JAY-peg”)
A standard developed by the Joint Photographic
Experts Group within ISO.
Lossy compression