# Graphics 101

### Image-based vs. Object-based Graphics

in Tutorials
There’s a very basic distinction in kinds of pictures (and therefore kinds of graphics) we use with computers. The difference is really simple, but very difficult to describe precisely. In fact, we don’t even have great words for the two categories. In the old days, they referred to the two types as “raster” and “vector”. I prefer “image-based” and “object-based”. Here’s a first attempt at the definitions: An image-based (or raster) graphic represents the pictures by measuring the color at a pre-determined set of locations (usually a grid). Read more…

### Color: Initial Answers to a Practical Question

in Tutorials
Color is complicated. There is a ton of stuff to learn. Later in class, we’ll discuss color more – and just scratch the surface of its complexity. But, between now and then you need to make pictures and you will want to specify what colors are in them. So here’s a short version… Can I really represent Color as 3 Numbers? In terms of the physics of light: you cannot. In terms of the perceptual science (psychology): in theory, 3 numbers are sufficient to capture what people can see. Read more…

### Points, Vectors and Coordinate Systems

in Tutorials
It always bugged me that math books made a big deal of the difference between points and vectors. They’re both just a list of numbers, right? In practice, yes, they are both lists of numbers. But getting an idea of what the difference is helps develop the intuition of coordinate system. To describe this, let me use an analogy/example: describing walking in a room. Assume that you know which way is north. Read more…

### What is a Pixel? (and what is a point sample?)

in Tutorials
When we talk about image-based graphics, we talk about it being a regular collection (usually a grid) of samples (or pixels). It’s time to be a little more precise about this. The term pixel is (I’m told) short for the term “picture element.” (Wikipedia, of course talks about this) Unfortunately, there is an ambiguity when we talk about a grid. And for reasons that we become clearer later, it is better to think about pixels one way rather than the other. Read more…