This lesson will look at what is a raster image and what is a vector image. Many people get confused with the tow. A good thorough knowledge of both is essential when you are looking at working with computers and graphics. In computer graphics, a raster graphics image or bitmap is a data structure representing a rectangular grid of pixels, or points of color, viewable via a monitor, paper, or other display medium. On the other hand vector graphics files store the lines, shapes and colours that make up an image as mathematical formulas.
Here is a raster / bitmap image
This photo is a classic example of what we classify as a raster image. The image is made up of a series of dots or pixels. Raster graphics are resolution dependent. They cannot scale up to an arbitrary resolution without loss of apparent quality. This property contrasts with the capabilities of vector graphics, which easily scale up to the quality of the device rendering them. Raster graphics deal more practically than vector graphics with photographs and photo-realistic images.
Zooming in shows the pixels of a raster image
Here is a zoomed in picture of the tiger we previously looked at. You will notice that image is being displayed by pixels. This is what a raster image is composed of. Each raster image is also always a rectangle. Every notice when you scan in an image or bring in a photo? They are always some form of a rectangle.
Scanned images are bitmaps
Here is a scanned logo that is imported into CorelDraw. Becasue it was scanned it is a raster image or bitmap
Vector Illustration of a Cat
Because vector images are represented by mathematical formula than they are considered to be resolution independent. Thus if I want to make a 2 inch vector illustration 10 inches there is no loss in quality. This is not the case for a bitmap or raster image. As the image is increased in size the resolution goes down as so does the quality of the image.
Zoomed in view of the cat
Unlike the original picture of the cat (raster image) the vector image does not show any pixels as did the cat. Thus vector graphics are treated differently than raster images
High End Vector Illustration
Here is an example of a vector drawn image. Although the quality is amazing the image is still not as good a raster image – photograph.
Here is a raster / bitmap image of a ferrari
Here is a bitmap image of a ferrari better known as a photograph
Should I use a vector object or a raster object
The big question is which type of object should I use with my laser or sublimation? Well when it comes to a picture the best is going to be the raster image as this is the only way it can be printed. However when it comes to text or to most logos usually the vector object is going to produce a better image. Typically this is because there is no degradation at the edges of the image.
Here is vector logo
Here we have zoomed in on a vectored logo. You can see that the quality along the edge of the image is excellent.
Here is a raster image
Here we have zoomed in on a raster or bitmap image of the same logo. Notice the pixelation long the edge of the borders of the image.
Notice that the straight edges are alright
On a raster image the straight edges are fine it is the curves where you loose the detail
Here is the same logo and view
As you can see the vector representation of this logo is not pixelated like the raster image. So when it comes to working with images such as logos it is best to always get a vector representation of the logo. Not only because the quality will be better but also if you have to increase the size than it i will not loose its quality as it goes up. Plus if you have to have to change a colour in the image than it is easier with the vector image.
Vector lines that engrave as vectors
The real confusion for most newcomers is that a vector can laser as a vector or as a raster image. This is dependent on the line thickness of the vector. For example for my laser if the line thickness is less than .008 to hairline than it will engrave as a vector. A vector forces the laser to recreate the shape of the vector that it is mimicking.
Vector image that engraves as a raster image
Any line that is bigger than .003 in width will laser as a raster image. The reason we do this is because the laser beam is fixed in width and if we want a wide border than the only way we can achieve this is to convert the image to a raster image and laser it the same way as a raster image.