dested/bezier.html

## bezier.html
<html>
   <head>
      <title>Bezier</title>
   </head>
   <body>
      <canvas id="canvas" width="1500" height="1200"></canvas>
      <input type="range" value="0.5" oninput="updateBezier(this.value)" min="0" max="1" step="0.005" style="position:absolute; width:98%; left:0; top:0;" />
      <script type="text/javascript">
         function Point(x, y) {
         this.x = x;
         this.y = y;
         }

         function Line(p1, p2) {
         this.Point1 = p1;
         this.Point2 = p2;
         }

         Line.prototype.lerp = function(f) {
         return new Point(lerp(this.Point1.x, this.Point2.x, f), lerp(this.Point1.y, this.Point2.y, f));
         }

         var canvas = document.getElementById('canvas');
         var context = canvas.getContext('2d');


         var circleRadius = 10;
         var rangeStep = 0.005;
         var scale = 2;
         var currentAnimateOffset = 0.5;

         var p1 = new Point(250, 300);
         var p2 = new Point(350, 300);

         var p1Handle = new Point(100, 50);
         var p2Handle = new Point(500, 50);


         var bezierPoints = [];
         var l1, l2, l3;

         function calculateBezier() {

         l1 = new Line(p1, p1Handle);
         l2 = new Line(p1Handle, p2Handle);
         l3 = new Line(p2Handle, p2);
         bezierPoints = [];

         for (var f = 0; f <= 1; f += rangeStep) {

             bezierPoints.push(calcBezierLerp(f));

         };

         }

         function calcBezierLerp(f) {
         var pl1 = l1.lerp(f);
         var pl2 = l2.lerp(f);
         var pl3 = l3.lerp(f);

         var bpl1 = new Line(pl1, pl2);
         var bpl2 = new Line(pl2, pl3);

         var cpl1 = bpl1.lerp(f);
         var cpl2 = bpl2.lerp(f);

         var dpl = new Line(cpl1, cpl2);
         var p = dpl.lerp(f);

         return {
             pl1: pl1,
             pl2: pl2,
             pl3: pl3,
             bpl1: bpl1,
             bpl2: bpl2,
             cpl1: cpl1,
             cpl2: cpl2,
             dpl: dpl,
             p: p
         };

         }

         function draw() {
         canvas.width = canvas.width;
         context.save();
         context.scale(scale, scale)

         context.save();
         context.lineWidth = 5;
         context.beginPath();
         context.moveTo(bezierPoints[0].p.x, bezierPoints[0].p.y);
         for (var i = 1; i < bezierPoints.length; i++) {
             context.lineTo(bezierPoints[i].p.x, bezierPoints[i].p.y);
         };
         context.stroke();
         context.restore();


         context.save();
         context.beginPath();
         context.moveTo(l1.Point1.x, l1.Point1.y);
         context.lineTo(l1.Point2.x, l1.Point2.y);
         context.stroke();
         context.restore();

         context.save();
         context.setLineDash([4, 4])
         context.beginPath();
         context.moveTo(l2.Point1.x, l2.Point1.y);
         context.lineTo(l2.Point2.x, l2.Point2.y);
         context.stroke();
         context.restore();

         context.save();
         context.beginPath();
         context.moveTo(l3.Point1.x, l3.Point1.y);
         context.lineTo(l3.Point2.x, l3.Point2.y);
         context.stroke();
         context.restore();

         context.save();
         drawCircle(p1Handle, circleRadius, 5);
         drawCircle(p2Handle, circleRadius, 5);


         drawCircle(p1, circleRadius, 5);
         drawCircle(p2, circleRadius, 5);
         context.restore();

         context.restore();

         drawLerp(currentAnimateOffset);
         }


         function drawLine(point1, point2, width) {
         context.save();
         context.lineWidth = width;
         context.beginPath();
         context.moveTo(point1.x, point1.y);
         context.lineTo(point2.x, point2.y);
         context.stroke();
         context.restore();
         }

         function drawLerp(f) {
         context.save();
         context.scale(scale, scale);

         var bp = bezierPoints[(1 / rangeStep * f) | 0];


         drawLine(bp.pl1, bp.pl2, 1);
         drawLine(bp.pl2, bp.pl3, 1);
         drawCircle(bp.pl1, 5, 3);
         drawCircle(bp.pl2, 5, 3);
         drawCircle(bp.pl3, 5, 3);


         drawLine(bp.cpl1, bp.cpl2, 1);
         drawCircle(bp.cpl1, 3, 2);
         drawCircle(bp.cpl2, 3, 2);


         drawCircle(bp.p, 6, 1, 'red');

         context.restore();
         }


         function drawCircle(point, radius, lineWidth, color) {
         var centerX = point.x;
         var centerY = point.y;
         color = color || 'green';
         context.save();
         context.beginPath();
         context.arc(centerX, centerY, radius, 0, 2 * Math.PI, false);
         context.fillStyle = color;
         context.fill();
         context.lineWidth = lineWidth;
         context.strokeStyle = '#003300';
         context.stroke();
         context.restore();
         }


         function lerp(a, b, f) {
         return a + f * (b - a);
         }

         function pointInCircle(point, centerOfCircle, radius) {
         var x = point.x;
         var y = point.y;
         var centerX = centerOfCircle.x;
         var centerY = centerOfCircle.y;
         return Math.pow((x - centerX), 2) + Math.pow((y - centerY), 2) <= Math.pow(radius, 2);
         }

         var selectPoint;

         canvas.onmousedown = function(e) {
         var ePoint = new Point(e.x / scale, e.y / scale);

         if (pointInCircle(ePoint, p1, circleRadius)) {
             selectPoint = p1;
         } else if (pointInCircle(ePoint, p2, circleRadius)) {
             selectPoint = p2;
         } else if (pointInCircle(ePoint, p1Handle, circleRadius)) {
             selectPoint = p1Handle;
         } else if (pointInCircle(ePoint, p2Handle, circleRadius)) {
             selectPoint = p2Handle;
         }
         }
         canvas.onmouseup = function(e) {
         selectPoint = undefined;
         }

         canvas.onmousemove = function(e) {
         if (!selectPoint) return;

         var ePoint = new Point(e.x / scale, e.y / scale);

         selectPoint.x = ePoint.x;
         selectPoint.y = ePoint.y;


         calculateBezier();
         draw();


         return false;
         }

         function updateBezier(f) {
         currentAnimateOffset = f;
         draw();
         }

         calculateBezier();
         draw();
      </script>
   </body>
</html>
	<html>
	<head>
	<title>Bezier</title>
	</head>
	<body>
	<canvas id="canvas" width="1500" height="1200"></canvas>
	<input type="range" value="0.5" oninput="updateBezier(this.value)" min="0" max="1" step="0.005" style="position:absolute; width:98%; left:0; top:0;" />
	<script type="text/javascript">
	function Point(x, y) {
	this.x = x;
	this.y = y;
	}

	function Line(p1, p2) {
	this.Point1 = p1;
	this.Point2 = p2;
	}

	Line.prototype.lerp = function(f) {
	return new Point(lerp(this.Point1.x, this.Point2.x, f), lerp(this.Point1.y, this.Point2.y, f));
	}

	var canvas = document.getElementById('canvas');
	var context = canvas.getContext('2d');



	var circleRadius = 10;
	var rangeStep = 0.005;
	var scale = 2;
	var currentAnimateOffset = 0.5;

	var p1 = new Point(250, 300);
	var p2 = new Point(350, 300);

	var p1Handle = new Point(100, 50);
	var p2Handle = new Point(500, 50);


	var bezierPoints = [];
	var l1, l2, l3;

	function calculateBezier() {

	l1 = new Line(p1, p1Handle);
	l2 = new Line(p1Handle, p2Handle);
	l3 = new Line(p2Handle, p2);
	bezierPoints = [];

	for (var f = 0; f <= 1; f += rangeStep) {

	bezierPoints.push(calcBezierLerp(f));

	};

	}

	function calcBezierLerp(f) {
	var pl1 = l1.lerp(f);
	var pl2 = l2.lerp(f);
	var pl3 = l3.lerp(f);

	var bpl1 = new Line(pl1, pl2);
	var bpl2 = new Line(pl2, pl3);

	var cpl1 = bpl1.lerp(f);
	var cpl2 = bpl2.lerp(f);

	var dpl = new Line(cpl1, cpl2);
	var p = dpl.lerp(f);

	return {
	pl1: pl1,
	pl2: pl2,
	pl3: pl3,
	bpl1: bpl1,
	bpl2: bpl2,
	cpl1: cpl1,
	cpl2: cpl2,
	dpl: dpl,
	p: p
	};

	}

	function draw() {
	canvas.width = canvas.width;
	context.save();
	context.scale(scale, scale)

	context.save();
	context.lineWidth = 5;
	context.beginPath();
	context.moveTo(bezierPoints[0].p.x, bezierPoints[0].p.y);
	for (var i = 1; i < bezierPoints.length; i++) {
	context.lineTo(bezierPoints[i].p.x, bezierPoints[i].p.y);
	};
	context.stroke();
	context.restore();


	context.save();
	context.beginPath();
	context.moveTo(l1.Point1.x, l1.Point1.y);
	context.lineTo(l1.Point2.x, l1.Point2.y);
	context.stroke();
	context.restore();

	context.save();
	context.setLineDash([4, 4])
	context.beginPath();
	context.moveTo(l2.Point1.x, l2.Point1.y);
	context.lineTo(l2.Point2.x, l2.Point2.y);
	context.stroke();
	context.restore();

	context.save();
	context.beginPath();
	context.moveTo(l3.Point1.x, l3.Point1.y);
	context.lineTo(l3.Point2.x, l3.Point2.y);
	context.stroke();
	context.restore();

	context.save();
	drawCircle(p1Handle, circleRadius, 5);
	drawCircle(p2Handle, circleRadius, 5);


	drawCircle(p1, circleRadius, 5);
	drawCircle(p2, circleRadius, 5);
	context.restore();

	context.restore();

	drawLerp(currentAnimateOffset);
	}


	function drawLine(point1, point2, width) {
	context.save();
	context.lineWidth = width;
	context.beginPath();
	context.moveTo(point1.x, point1.y);
	context.lineTo(point2.x, point2.y);
	context.stroke();
	context.restore();
	}

	function drawLerp(f) {
	context.save();
	context.scale(scale, scale);

	var bp = bezierPoints[(1 / rangeStep * f) \| 0];


	drawLine(bp.pl1, bp.pl2, 1);
	drawLine(bp.pl2, bp.pl3, 1);
	drawCircle(bp.pl1, 5, 3);
	drawCircle(bp.pl2, 5, 3);
	drawCircle(bp.pl3, 5, 3);



	drawLine(bp.cpl1, bp.cpl2, 1);
	drawCircle(bp.cpl1, 3, 2);
	drawCircle(bp.cpl2, 3, 2);



	drawCircle(bp.p, 6, 1, 'red');

	context.restore();
	}



	function drawCircle(point, radius, lineWidth, color) {
	var centerX = point.x;
	var centerY = point.y;
	color = color \|\| 'green';
	context.save();
	context.beginPath();
	context.arc(centerX, centerY, radius, 0, 2 * Math.PI, false);
	context.fillStyle = color;
	context.fill();
	context.lineWidth = lineWidth;
	context.strokeStyle = '#003300';
	context.stroke();
	context.restore();
	}



	function lerp(a, b, f) {
	return a + f * (b - a);
	}

	function pointInCircle(point, centerOfCircle, radius) {
	var x = point.x;
	var y = point.y;
	var centerX = centerOfCircle.x;
	var centerY = centerOfCircle.y;
	return Math.pow((x - centerX), 2) + Math.pow((y - centerY), 2) <= Math.pow(radius, 2);
	}

	var selectPoint;

	canvas.onmousedown = function(e) {
	var ePoint = new Point(e.x / scale, e.y / scale);

	if (pointInCircle(ePoint, p1, circleRadius)) {
	selectPoint = p1;
	} else if (pointInCircle(ePoint, p2, circleRadius)) {
	selectPoint = p2;
	} else if (pointInCircle(ePoint, p1Handle, circleRadius)) {
	selectPoint = p1Handle;
	} else if (pointInCircle(ePoint, p2Handle, circleRadius)) {
	selectPoint = p2Handle;
	}
	}
	canvas.onmouseup = function(e) {
	selectPoint = undefined;
	}

	canvas.onmousemove = function(e) {
	if (!selectPoint) return;

	var ePoint = new Point(e.x / scale, e.y / scale);

	selectPoint.x = ePoint.x;
	selectPoint.y = ePoint.y;


	calculateBezier();
	draw();


	return false;
	}

	function updateBezier(f) {
	currentAnimateOffset = f;
	draw();
	}

	calculateBezier();
	draw();
	</script>
	</body>
	</html>