我想通过计算找到弧的终点和起点。
你可以输入
Range Raduis:150
范围起始角度:60
范围结束角度:160
link to screen shot demonstrating problem
非常感谢
function draw(val,StartAngle,EndAngle,XAxis,YAxis){
var canvas = document.getElementById('canvas');
var context = canvas.getContext('2d'),
x = 200,//center raduis
y = 400;//center raduis
d = EndAngle;//End Angle
s = StartAngle;//Start angle
X_Axis = XAxis;//feature to enable to move the circle on axis X
Y_Axis = YAxis;// feature to enable to move the circle on axis Y
p ={}
p.r = val;
p.d = d*2*Math.PI/360;
p.s = s*2*Math.PI/360;
p.x = X_Axis + p.d*Math.cos(p.r);
p.y = Y_Axis + p.d*Math.sin(p.r);
p.pex = p.x + p.r*Math.cos(d);
p.pey = p.y - p.r*Math.sin(s);
p.psx = p.x - Math.sin(s) * p.r;
p.psy = p.y - Math.cos(s) * p.r ;
context.clearRect(0, 0, canvas.width, canvas.height);
context.beginPath();
context.lineWidth = 1;
context.arc(p.x ,p.y ,p.r,p.s,p.d);
context.fillStyle = 'green';
context.fillRect(x,y+val,2,2); // crnter circle
context.fillStyle = 'yellow';
context.moveTo(x-p.d,y+p.d);
context.lineTo(x+p.d,y+p.d);
context.stroke();
// line color
context.strokeStyle = 'black';
context.stroke();
// Cut off the top of the circle.
//context.clearRect(0, 0, canvas.width, y);
// This stuff's just to show some dots
context.fillStyle = 'red';
context.fillRect(x-1,y-1,2,2); // Middle
context.fillRect(p.pex,p.pey,4,4);//Target point 1
context.fillRect(p.psx,p.psy,4,4);// Target point 2
context.fillRect(x-2,y+d+val-2,4,4); // Point on circle
context.fillStyle = 'black';
}
答案 0 :(得分:4)
var r_length = ... // radius
var r_start_angle = RangeStartAngle / 360 * 2 * Math.PI; // lets convert degrees to radians
var r_end_angle = RangeEndAngle / 360 * 2 * Math.PI;
开始位置
x = circle_center_x + Math.cos(r_start_angle) * r_length;
y = circle_center_y + Math.sin(r_start_angle) * r_length;
结束职位
x = circle_center_x + Math.cos(r_end_angle) * r_length;
y = circle_center_y + Math.sin(r_end_angle) * r_length;
画弧
context.arc(circle_center_x ,circle_center_y, r_start_angle, r_end_angle);
您可能想要使用该知识重写您的功能