Concepts of raster and vector graphics

 

Raster graphics or bitmap is collection of data representing a rectangle net of pixels or colored points on a graphic output device like monitor or on paper. Pixel is abbreviation for Picture Element, representing one point on graphics. Monitors show picture by dividing whole screen on thousands (or millions) of pixels organized in rows and columns. Since pixels are very small, they look connected.

 

Number of bits used to represent one pixel determines how many colors can be shown. Each color of an individual pixel is particularly defined, so RGB (Red, Green, Blue) pictures contain three bytes per pixel, while each byte contains one particularly defined color.

 

Quality of a raster image is determined by total number of pixels (resolution) and by the number of values for every single pixel (color depth). If color depth is bigger, more tones can be shown meaning that you get a better picture and higher quality view. Resolution refers to sharpness and clarity of an image. Term resolution is most oftenly used to describe characteristics of monitors, printers and raster graphics.

 

File size wise, bitmap files are not compressed, so an optimal image format should be chosen. Bitmap graphics can be compressed by saving them in JPG format, which reduces colors on pictures, decreases the file size, and ireversibly loses information. Bitmap graphics can be saved in any of the following formats: GIF, JPG, TIFF, BMP, PICT, PNG i PCX.

 

Raster graphics can not be increased to higher resolution without quality loss, which is not case for vector graphics. Raster graphics is more practicle than vector graphics for photographers and common users. Vector graphics is used by graphic designers and DTP editors. Previous monitors could show from 72 to 130 pixels per inch (PPI), while current printers can print 2400 points per inch (DPI).

 

Vector graphics or geometric modeling is a way of showing an image by using geometric shapes like points, lines, curves and polygons, all based on mathematic equations.

 

It is much easier to remember vector graphics than demanding raster (bitmap) pictures. Almost all nowadays computer graphic views convert vector image to raster format. Raster picture is kept in memory and contains data for each single pixel of a picture. Term vector graphics is used in context of two-dimensional computer graphics.