Raster or Vector Graphics

Your digital pictures and most of the photos you see on the internet are raster images; that is, they are made up of multitudes of squares, which make up a bitmap, or series of pixels. When you try to enlarge a digital picture, you may notice that the picture takes on a blocky or blurred appearance. Raster images need to be rescaled by a factor of 8 for the printer settings to compensate, so it is tricky to do much re-scaling with raster art. You can change tonal values, color values, and adjust the saturation settings with much more ease. When you are working on a digital picture in Photoshop you will see that when you erase something or change it, the pixels in the background change with it.

Now suppose you are working on a line drawing in one of your programs, like Corel Draw or Illustrator: You are working on a vector image which is also known as outlines, paths, or curves. Lines are connected to one another by tiny little points known as “nodes”. When you attempt to make changes to your vector drawings, you do this by manipulating the nodes. If you are a skilled graphic artist you know that if you remove or add new nodes to the outlined drawing, then you change the shape either gradually or drastically, depending on how many nodes you manipulate. However, you have great flexibility when working with vector images. As long as you have a closed path, you can fill in the shape or object with color.

Using a program like Corel Draw, you can make a raster image easier to work on by means of vector tracing. This is a simple and quick procedure depending on how many nodes comprise the picture, leaving you with a picture in vector outlined format. When I do this I use a tool called “Quick Trace”. Results can vary whether I am using Outline trace, Quick Trace, or Centerline Trace. Vector images scale well and are also used in flash animations.

Also, files can vary as well depending on whether you are using vector or raster art. Vector art is lossless meaning that file compression will not result in loss of image quality. A good example of lossless formats would be.GIF. In raster image JPEGs, permanent loss of data to reduce file size can occur. This is because JPEG format is a lossy compression… meaning that there may be some loss of image quality to be expected when the picture is compressed. This could present a problem in projects in which details are important, like spreadsheets. This type of loss is more acceptable for video and sound files, in which the loss is not significant enough to be detected.