When programming with graphics in any computer language, there are certain basic ideas
which are common to all contexts. This tutorial page will tell you how to do simple
drawing in general, because each computer language and operating system has different
methods of actually doing the drawing. If you've never done graphics programming before,
this is a good place to begin.
Computer graphics use a different coordinate system than you were taught in mathematics
courses. Instead of the bottom left being the point (0,0), the top left represents
that point. Especially when you first begin to do graphics programming, this can be
confusing. One solution, if you like the "normal" system better is to write a simple
function which will convert the coordinates. Depending on the language, this can be done
with two functions, or one function (especially easy if you use pointers in C/C++).
If you want to draw anything that looks remotely nice, however, colors are important.
In general, colors are either specified using indexed color or a color system such as
RGB. Once again, the specifics depend on the language and OS. Briefly, indexed color
means that there is an enumerated index of all the available colors and the graphics
call that changes the color specifies one of these. For example, you might have 16 colors
available, and the individual numbers could correspond to system defined colors. One might
be red, and two might be orange.
With the Red-Green-Blue system, however, colors are specified according to their separate
values for each of these colors. In order to create a new color, the colors of light are
blended. If all colors of light are blended, the result is white. No intensity for each
color, predictably, give you black. Using this method, or a similar one, all colors can
be created. The limiting factors, however, are the display, video card, and also the number
of bits each color is represented with.
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