What would be better than the old X eyes? The eyes following your cursor...
How to calculate where to put the inner eye
// pos1X,Y is the middle of the eye in global coordinates
var dx = cursorX - this.pos1X;
var dy = cursorY - this.pos1Y;
var distance = Math.sqrt(dx*dx+dy*dy);
var x = (distance < this.radius)? dx : dx*this.radius/distance;
var y = (distance < this.radius)? dy : dy*this.radius/distance;
// eye1X,Y is the middle of the eye in canvas coordinates
this.drawEye(this.eye1X+x, this.eye1Y+y);
The complete code, have fun:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset=utf-8>
<script src="../lib/jquery.js"></script>
<style> body { text-align: center }</style>
<title>HTML5 Demo: Canvas with Eyes</title>
<script>
window.onload = function() {
var eyes = {
drawEye: function (x, y) {
this.ctx.beginPath();
this.ctx.arc(x, y, this.radius, 0, 2*Math.PI, false);
this.ctx.fill();
this.ctx.closePath();
},
drawSmiley: function () {
// clear the canvas
this.canvas.width = this.canvas.width;
// The large circle
this.ctx.beginPath();
this.ctx.arc(this.midX,this.midY,this.midX-2,0,Math.PI*2,true);
// The mount drawn clockwise
var mouthR = Math.floor(this.midX * 2 / 3);
this.ctx.moveTo(this.midX+mouthR,this.midY);
this.ctx.arc(this.midX,this.midY,mouthR,0,Math.PI,false);
// first eye
this.ctx.moveTo(this.eye1X+this.outline,this.eye1Y);
this.ctx.arc(this.eye1X,this.eye1Y,this.outline,0,Math.PI*2,true);
// second eye
this.ctx.moveTo(this.eye2X+this.outline,this.eye2Y);
this.ctx.arc(this.eye2X,this.eye2Y,this.outline,0,Math.PI*2,true);
this.ctx.stroke();
},
lookAt: function(cursorX, cursorY) {
// calc global position for comparing with the mouse position
var pos1X = this.eye1X + this.canvas.offsetLeft;
var pos1Y = this.eye1Y + this.canvas.offsetTop;
var pos2X = this.eye2X + this.canvas.offsetLeft;
var pos2Y = this.eye2Y + this.canvas.offsetTop;
// first eye
var dx = cursorX - pos1X;
var dy = cursorY - pos1Y;
var distance = Math.sqrt(dx*dx+dy*dy);
var x = (distance < this.radius)? dx : dx*this.radius/distance;
var y = (distance < this.radius)? dy : dy*this.radius/distance;
this.drawEye(this.eye1X+x, this.eye1Y+y);
// second eye
dx = cursorX - pos2X;
dy = cursorY - pos2Y;
distance = Math.sqrt(dx*dx+dy*dy);
x = (distance < this.radius)? dx : dx*this.radius/distance;
y = (distance < this.radius)? dy : dy*this.radius/distance;
this.drawEye(this.eye2X+x, this.eye2Y+y);
},
init: function(theCanvas) {
// get a drawing context
this.canvas = theCanvas;
this.ctx = theCanvas.getContext("2d");
// calculate the middle of the canvas
this.midX = Math.floor(this.canvas.width / 2);
this.midY = Math.floor(this.canvas.height / 2);
// calculate the middle of the 2 eyes on 1/3 and 2/3 of the canvas
this.eye1X = Math.floor(this.canvas.width * 1 / 3);
this.eye1Y = Math.floor(this.canvas.height * 2 / 5);
this.eye2X = Math.floor(this.canvas.width * 2 / 3);
this.eye2Y = this.eye1Y;
// radius = iris, outline = total eye
this.radius = this.canvas.width / 20;
this.outline = this.radius * 2;
}
};
eyes.init( document.getElementById("eyes") );
eyes.drawSmiley();
document.onmousemove = function(evt) {
eyes.drawSmiley();
eyes.lookAt(evt.clientX, evt.clientY);
};
};
</script>
</head>
<body>
<header>
<h1>Canvas</h1>
</header>
<canvas width=200 height=200 id=eyes></canvas>
<p>Wie kijkt naar waar?</p>
</body>
</html>