Images are everywhere in our lives: on our televisions, on our computer screens, in our mail boxes, on buses, signs, lamp posts, store windows, the list can go on and on.
But as individuals that are involved in the economy of those images – designers and publishers – there are a few basic notions about these images that we need to know. The most important and basic of which is that of the raster image versus the vector image.
Within the world of images, there are two types of final products: print and digital. You can have both raster and vector images in both print and online. And since all images start out digitally these days, I am going to begin in the digital world.
A RASTER IMAGE is an image that is made up of millions and millions of tiny squares called pixels. Each one of these tiny pixels is a different color and when viewed as a whole by your eye, it all blends together to make one whole image. Figure A shows a raster image zoomed in 1200% to see a glimpse of the individual pixels (squares) that make up the picture as a whole.
Raster images provide us with the most detail as each individual square is colored with one of millions and millions of colors contained in the color spectrum of the universe. But one drawback of the raster image, is that the pixels are finite. There are only so many pixels within any given image. So while you can take away pixels (make the image smaller) without any loss of quality, you absolutely cannot add to the image (make larger) without a significant loss of quality.
The reason for this is that when you enlarge a raster image, you have to add pixels to the image. Your computer takes the original data from the image, blows it up to the size you want, and then randomly selects colors to fill in the pixel gaps that were not there in the first place. And to make matters worse, computers cannot see the image as a whole. They have no idea what a picture is. They don’t know that you might be looking at an image of a horse. They only see the data contained in each pixel. So to enlarge the image it just makes things up. It tries to do its best by sampling colors from close by, but what begins to appear is what we call image “noise”. Figure B1 shows a small image that is enlarged 550% to Figure B2. You can see the difference in quality between the original image and the upsized image.
Figure B1
Figure B2
A VECTOR IMAGE on the other hand, is an image that is made up of a mathematical formula. Meaning that the image is made up of lines, circles, squares, triangles – all basic shapes that have mathematical formulas behind them. A circle can be red, a square can be turquoise, or any other shape or color. Figure C shows two examples of vector images. Try to find the basic shapes in the images.
Because a square is a square and a circle is a circle, vector images can be resized TO ANY SIZE without any loss of quality. The formula for each image size is the same whether the image is one inch by one inch or the size of a bill board! And, VECTOR images can ALWAYS be turned into RASTER images. You can take a snapshot of a vector image and view it as millions and millions of pixels (you do that already when you view a vector image on your computer screen).
There are a few instances when you can reverse the process and turn a raster image into a vector image, but that process is much more challenging and is fretted with many different pitfalls. It is best to stay in the vector to raster direction when it comes to image conversions.
Stay tuned to the next article where I will discuss raster images more in depth as I explore the “Rules of Resolution – and why you should know!”
**All images used with permission.
