Graphic images that have been processed by a computer can usually be divided into two distinct categories. Such images are either bitmap files or vector graphics. If you work in prepress, you need a good comprehension on the advantages and disadvantages of both types As a general rule scanned images are bitmap files while drawings made in applications like Corel Draw or Illustrator are saved as vector graphics. But you can convert images between these two data types and it is even possible to mix them in a file. This sometimes confuses people. of data. are exactly what their name says they are: a collection of bits that form an image. The image consists of a matrix of individual dots (or pixels) that all have their own colour (described using bits, the smallest possible units of information for a computer). Here you see an image and to the right top a 250 percent enlargement. As you can see the image consists of hundreds of rows and columns of small elements that all have their own colour. One such element is called a pixel -short for picture element). The human eye is not capable of seeing each individual pixel so we perceive a picture with smooth gradations. These are images that only contain two colours, usually black and white. Sometimes these images are referred to as bitmaps because a computer has to use only 1 bit (on=black, off=white) to define each pixel. This images contain shades of two or more colours. The most popular multitone images are duotones, which usually consist of black and a second spot colour (often an Pantone colour). Bitmap data can take up a lot of room. A CMYK A4-size picture that is optimized for medium quality printing (150 lpi) takes up 40 MB. Compression can reduce the size of the file. Oone of the main disadvantages of bitmap images: once they are enlarged to much, they look unnatural and blocky. But reducing a picture too much also has a bad influence as it looses sharpness. There are hundreds of applications on the market that can be used to create or modify bitmap data. In prepress Adobe PhotoShop, are the best. versatile file format that can contain just about any type of data including complete pages, not yet widely used to exchange just images Each individual line is made up of either a vast collection of points with lines interconnecting all of them or just a few control points that are connected using so called bezier curves. It is this latter method that generates the best results and that is used by most drawing programs. Vector drawings are usually pretty small files because they only contain data about the bezier curves that form the drawing. Vector drawings can usually be scaled without any loss in quality. This makes them ideal for company logo's, maps or other objects that have to be resized frequently. Please note that not all vector drawings can be scaled as much as you like: It is fairly easy to create a vector based drawing that is very difficult to output. Especially the use of tiles (small objects that are repeated dozens or hundreds of times) and Corel Draw lens effects can lead to very complex files. There are hundreds of applications on the market that can be used to create or modify vector data. In prepress, Adobe Illustrator and Corel Draw are the most popular. Source.


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Last Modified: May 16, 2016 @ 3:03 am