var canvas = document.getElementById("canvas");
canvas.width = 800;
canvas.height = 800;
context = canvas.getContext("2d");
context.beginPath();
context.strokeStyle = "red";
context.linewidth = 10;
context.moveTo(10, 10);
context.lineTo(50, 50);
context.stroke();
context.endPath();
canvas.width = 800;
canvas.height = 800;
context = canvas.getContext("2d");
context.beginPath();
context.strokeStyle = "red";
context.linewidth = 10;
context.moveTo(10, 10);
context.lineTo(50, 50);
context.stroke();
context.endPath();
const 繪制多邊形=(邊數,偏移橫坐標,偏移縱坐標,半徑)=>{
const 平分角度=360/邊數, 圓周率=Math.PI
for (let 索引=0;索引<邊數;索引++){
let 橫坐標=Math.cos(((90-平分角度+平分角度*索引)*圓周率)/180)*半徑+偏移橫坐標
let 縱坐標=-Math.sin(((90-平分角度+平分角度*索引)*圓周率)/180)*半徑+偏移縱坐標
ctx.lineTo(橫坐標,縱坐標)
}
}
const 平分角度=360/邊數, 圓周率=Math.PI
for (let 索引=0;索引<邊數;索引++){
let 橫坐標=Math.cos(((90-平分角度+平分角度*索引)*圓周率)/180)*半徑+偏移橫坐標
let 縱坐標=-Math.sin(((90-平分角度+平分角度*索引)*圓周率)/180)*半徑+偏移縱坐標
ctx.lineTo(橫坐標,縱坐標)
}
}
2018-10-31