Html5 Canvas開發之畫圓（時鐘，貝塞爾曲線）和旋轉縮放

1.時鐘

<script>

window.onload = function(){
	var oC = document.getElementById('c1');
	var oGC = oC.getContext('2d');
	
	function toDraw(){
		
		var x = 200;
		var y = 200;
		var r = 150;
		
		oGC.clearRect(0,0,oC.width,oC.height);
		
		var oDate = new Date();
		var oHours = oDate.getHours();
		var oMin = oDate.getMinutes();
		var oSen = oDate.getSeconds();
		
		var oHoursValue = (-90 + oHours*30 + oMin/2) * Math.PI/180;
		var oMinValue = (-90 + oMin*6) * Math.PI/180;
		var oSenValue = (-90 + oSen*6) * Math.PI/180;
		
		
		/*oGC.moveTo(x,y);
		
		oGC.arc(x,y,r,0,6*Math.PI/180,false);
		
		oGC.moveTo(x,y);
		
		oGC.arc(x,y,r,6*Math.PI/180,12*Math.PI/180,false);*/
		
		oGC.beginPath();
		
		for(var i=0;i<60;i++){
			oGC.moveTo(x,y);
			oGC.arc(x,y,r,6*i*Math.PI/180,6*(i+1)*Math.PI/180,false);
		}
		
		oGC.closePath();
		
		oGC.stroke();
		
		
		
		oGC.fillStyle = 'white';
		
		oGC.beginPath();
		
		oGC.moveTo(x,y);
		oGC.arc(x,y,r*19/20,0,360*(i+1)*Math.PI/180,false);
		
		oGC.closePath();
		
		oGC.fill();
		
		
		oGC.lineWidth = 3;
		
		oGC.beginPath();
		
		for(var i=0;i<12;i++){
			oGC.moveTo(x,y);
			oGC.arc(x,y,r,30*i*Math.PI/180,30*(i+1)*Math.PI/180,false);
		}
		
		oGC.closePath();
		
		oGC.stroke();
		
		
		oGC.fillStyle = 'white';
		
		oGC.beginPath();
		
		oGC.moveTo(x,y);
		oGC.arc(x,y,r*18/20,0,360*(i+1)*Math.PI/180,false);
		
		oGC.closePath();
		
		oGC.fill();
		
		
		oGC.lineWidth = 5;
		
		oGC.beginPath();
		oGC.moveTo(x,y);
		
		oGC.arc(x,y,r*10/20,oHoursValue,oHoursValue,false);
		
		oGC.closePath();
		oGC.stroke();
		
		oGC.lineWidth = 3;
		oGC.beginPath();
		oGC.moveTo(x,y);
		
		oGC.arc(x,y,r*14/20,oMinValue,oMinValue,false);
		
		oGC.closePath();
		oGC.stroke();
		
		
		oGC.lineWidth = 1;
		oGC.beginPath();
		oGC.moveTo(x,y);
		
		oGC.arc(x,y,r*19/20,oSenValue,oSenValue,false);
		
		oGC.closePath();
		oGC.stroke();
		
		
	}
	
	setInterval(toDraw,1000);
	
	toDraw();
	
};

</script>

2.貝塞爾曲線

<script>

window.onload = function(){
	var oC = document.getElementById('c1');
	var oGC = oC.getContext('2d');
	
	/*oGC.moveTo(100,200);
	
	oGC.quadraticCurveTo(100,100,200,100);
	
	oGC.stroke();*/
	
	oGC.moveTo(100,200);
	
	oGC.bezierCurveTo(100,100,200,200,200,100);
	
	oGC.stroke();
	
};

</script>

3.旋轉縮放

<script>

window.onload = function(){
	var oC = document.getElementById('c1');
	var oGC = oC.getContext('2d');
	
	var num = 0;
	
	var num2 = 0;
	
	var value = 1;
	
	oGC.translate(200,200);
	
	setInterval(function(){
		
		num++;
		
		oGC.save();
		
		oGC.clearRect(0,0,oC.width,oC.height);
		
		if(num2 == 50){
			value = -1;
		}
		else if(num2 == 0){
			value = 1;
		}
		
		num2 += value;
		
		oGC.scale( num2*1/50,num2*1/50 );
		
		oGC.rotate(num*Math.PI/180);
		
		oGC.translate(-50,-50);
		
		oGC.fillRect(0,0,100,100);
		
		oGC.restore();  
		
	},30);
	
};

</script>