JAVASCRIPT
window.onload = function(){
var flag = document.getElementById('flag');
drawFlag( flag, 320, 0, 80 );
flag.style.marginLeft = -(flag.width/2)+'px';
flag.style.marginTop = -(flag.height/2)+'px';
var timer = waveFlag( flag, 20, 10, 150, 200, -0.1 );
};
function drawFlag( canvas, width, padX, padY ){
if (!padX) padX = 0;
if (!padY) padY = 0;
var a = width / 1.9;
var b = width;
var c = 7*a/13;
var d = 0.76*a;
var e = 0.054*a;
var g = 0.063*a;
var k = 0.0616*a;
var l = a / 13;
canvas.width = b+2*padX;
canvas.height = a+2*padY;
var ctx = canvas.getContext('2d');
// Stripes
ctx.fillStyle = "#118806";
ctx.fillRect(5,25,300,50);
ctx.fillStyle = "#118806";
ctx.fillRect(5,75,300,50);
ctx.fillStyle = "#118806";
ctx.fillRect(5,125,300,50);
}
function waveFlag( canvas, wavelength, amplitude, period, shading, squeeze ){
if (!squeeze) squeeze = 0;
if (!shading) shading = 100;
if (!period) period = 200;
if (!amplitude) amplitude = 10;
if (!wavelength) wavelength = canvas.width/10;
var fps = 30;
var ctx = canvas.getContext('2d');
var w = canvas.width, h = canvas.height;
var od = ctx.getImageData(0,0,w,h).data;
// var ct = 0, st=new Date;
return setInterval(function(){
var id = ctx.getImageData(0,0,w,h);
var d = id.data;
var now = (new Date)/(period);
for (var y=0;y<h;++y){
var lastO=0,shade=0;
var sq = (y-h/2)*squeeze;
for (var x=0;x<w;++x){
var px = (y*w + x)*4;
var pct = x/w;
var o = Math.sin(x/wavelength-now)*amplitude*pct;
var y2 = y + (o+sq*pct)<<0;
var opx = (y2*w + x)*4;
shade = (o-lastO)*shading;
d[px ] = od[opx ]+shade;
d[px+1] = od[opx+1]+shade;
d[px+2] = od[opx+2]+shade;
d[px+3] = od[opx+3];
lastO = o;
}
}
ctx.putImageData(id,0,0);
// if ((++ct)%100 == 0) console.log( 1000 * ct / (new Date - st));
},1000/fps);
}
