[Java] counint pixels using drawLine

[hanniph]

Hey,

I've started reading 'Computer graphics for Java programmers' and ran into this problem:

How many pixels are put on the screen by the following call?

g.drawLine (10, 20, 100, 50);

Both the answer 91 and the short explanation(100 - 10 + 1) are unclear to me. It would be great if somebody could explain it (for example, why we add 1?) or give some hints on this. I'm new to graphics

Thanks

[Reiger]

Fairly simple: consider the delta's in x and y coordinates. 90 and 30 respectively. There will be no duplicate x coordinates because 30 divides 90 cleanly (90/30 = 3).
In other words it works out as 3 to the right, per 1 down, i.e the line is approximated by placing pixels in a pattern like this where (.) is a single coloured pixel:

...
   ...
      ...

So 90 pixels to draw from (10,20) [inclusive] to (100,50) [exclusive], and one pixel to draw (100,50).

[hanniph]

Nice one. That's right, it wasn't that hard. Thanks for clearing this