# Adding Colors to Disappearing Dots

## July 30, 2012

This is a second iteration to the disappering dots.
As the title says, I’m adding colors to dots.
How about some nice color variations in blue.

I found a very minimum implementation of HSV to RGV conversion here: http://spphire9.wordpress.com/2011/03/03/javascript%E3%81%A7hsv%E3%81%8B%E3%82%89rgb%E5%A4%89%E6%8F%9B/

Hue is a random value from 200 to 240.
Saturation is between 50 to 100.
Value is also between 50 to 100.

Size of circles is also randomized this time.

Use of HSV, I learned from this lecture notes: http://yoppa.org/cuc_prog12/3766.html
It’s all in Japanese but code is in processing, so you don’t really need to read Japanese.

```window.onload = (function(win, doc) {
var c,
TWOPI = 2*Math.PI,
last = +(new Date()),
// a bit slower fading out
MY_BLACK = "rgba(0, 0, 0, 0.4)",
WIDTH = 400,
HEIGHT = 400;

var hsva(h, s, v, a) {
var f = h/60,
i = f^0,
m = v-v*s,
k = v*s*(f-i),
p = v-k,
q = k+m;
return 'rgba('
+[[v,p,m,m,q,v][i]*255^0,
[q,v,v,p,m,m][i]*255^0,
[m,m,q,v,v,p][i]*255^0,a].join(',')
+')';
}

function randomWithin(a, b) {
var diff = b - a;
var val = Math.floor(Math.random() * diff + a);
return val;
}

var randomPoint = function() {
return Math.floor(Math.random() * WIDTH  + 1);
}

var draw = function() {
var now = +(new Date());
c.fillStyle = MY_BLACK;
c.fillRect(0, 0, WIDTH, HEIGHT);
if (now - last > 1000) {
// hue being 200 to 240 generates bluish color variations
c.fillStyle = hsva(randomWithin(200, 240),
randomWithin(50, 100)/100,
randomWithin(50, 100)/100,
.5);
c.beginPath();
c.arc(randomPoint(), randomPoint(), 5, 0, TWOPI, true);
c.fill();
last = now;
}
win.requestAnimationFrame(draw);
}

var init = function() {
var canvas = doc.getElementById("ground");

c = canvas.getContext("2d");
c.fillStyle = "#000";
c.fillRect(0, 0, WIDTH, HEIGHT);

win.requestAnimationFrame(draw);
};

return init;
}(window, document));
```