Raster images are pixel based. Each [...]]]> When creating images – with or without layers – they are created as either a raster or a vector image or layer.  Most  graphics program are written to use  raster images and layers – with an option to create some text and object layers as vectors. So what’s the difference?

Raster Images

Raster images are pixel based. Each image is comprised of a collection of square ‘dots’ called pixels where each pixel is a colored square. If you were to zoom into a raster image you would be able to see each pixel as a colored square. When working with a raster image containing pixels you are in effect working with the whole image and anything you do affects the entire image. You know what I mean if you’ve ever tried to enlarge a raster image and ended up with an image that is out-of-focus and has jagged edges.

Vector Images

Vector images do not use pixels, but rather store the image information as a set of properties that describe the image relative to its attributes, dimensions and position inside the image. These attributes are displayed and manipulated through the use of nodes or drawing points on top of the image. You might say a vector image is a grouping of connected curves and lines that is object-oriented – kind of like a ‘connect-the-dots’ picture.

When working with vector images you have access to all of its properties with each element being independent. This means you can make changes without affecting the rest of the image. Since vector images are object-oriented, you can ‘re-size’ – or more correctly scale the image – without any loss of image quality. This makes it particularly useful for clip-art.

Not all graphics programs have the ability to work with vectors . . . so, if you are planning on working with vectors and your graphics program is not set up to specifically work with vector images – you will need to purchase a special program.

Using Raster and Vector Layers

Knowing the difference between raster and vector images/layers allows you to build images to suit your needs. Use raster layers for anything that is the correct size or can be down-sized without loosing any image quality. Use vector images for text and/or objects where you want to fill an area or focus attention. Using both raster and vector layers in an image is particularly useful for creating banner ads. However, just like oil and water don’t mix – you cannot place vector objects on individual raster layers nor can you place raster objects on individual vector layers.

For our example, we want to have a finished banner with the 5 individual layers listed below-

1. Background color
2. Logo image
3. Company name
4. Company slogan 
5. Graphic pointer 

Definition of individual layers:

1. Background color is a raster layer using a hexadecimal color (white)
2. Logo image is a raster layer using an image we could down-size  without loosing any image quality
3. Company name is a vector layer using vector text to fill in the whole top area of the banner
4. Company slogan is a raster layer using regular text
5. Graphic pointer is a vector layer where the object (arrow) was enlarged to fill in the white space drawing attention to the picture

Conclusion

Using raster and vectors by themselves or in layers to create images gives you a lot of flexibility to make your graphics look more professional and have the eye-catching appeal you want. I recently found a site that sells royalty-free graphics in the form of books and discs – best part is you can sign up and receive free graphics weekly. If you’re interested in getting on their email list visit www.doverpublications.com and click on Free Samples (at the bottom of the page).