Be Excellent To Each Other

So, imagine you've got a big old grid of little squares. Some might even call them pixels.

All these pixels are labelled grid-reference style, so top left is 0:0, top right is 0:100, middle is 50:50, etc (this assumes an overall size of 100x100, obviously).

So, say someone picks one of these points, maybe 21:45. How do I work out which pixelsI have to recolour to draw a 5 pixel radius circle around the chosen one?

I can do diamonds. Diamonds are easy. And squares and shit. I like right angles.

I can also do drinking. Maybe this will be easier in the morning.

It would be double easier if one of you tells me.

I asked paint.net and it said:

hmm, bit small.
Try this:



(obviously that's a non blended or anti-aliased one.)

So two rectangles then.

Cheap way (i.e easy for a computer to calculate)...
Process a square around the center point +/- the radius.
For each pixel, work out...
(x - center_x)*(x - center_x) + (y - center_y)*(y - center_y) - radius*radius
If this us <0 then fill it with the colour, otherwise leave it alone.
Huzzah for Pythagoras!

en.m.wikipedia.org/wiki/Midpoint_circle_algorithm

Midpoint Circle Algorithm might be your chum here!

You need to invent the squircle.

I realised that you asked for 5px radius, and this is 5px diameter. BAD. If I could be bothered I'd load up paint.net and use a size-9 brush and do the same. But that's less trivial. Just use the x^2+y^2-r=0 given above.

I'm sorry, I'm really not that into Pokemon.