我正在制作一些非常简单的 ui(健康/能量)栏,我决定使用由两半圆(红色/蓝色)制成的径向栏。为了计算两半的 Angular ,我使用了非常简单的工具:
var radians = function(angle) {
return (Math.PI / 180) * angle;
};
我可以像这样画每一半:
ctx.arc(cvs_wc, cvs_hc, 15, radians(270), radians(90);
ctx.arc(cvs_wc, cvs_hc, 15, radians(90), radians(270);
这样我就可以毫无问题地很好地画左半边和右半边了。
然而,当我想为其应用填充时,我看到它们在两个半 Angular 点(开始半 Angular 和结束半 Angular )之间填充。看起来不太好,我该如何修改代码,使填充始终从圆心开始,而不是从一半开始。
最佳答案
添加 ctx.moveTo();
/ctx.lineTo();
它会起作用。
/* General Settings ----> */
var cvs = document.getElementById('cvs');
var ctx = cvs.getContext('2d');
var cvs_w = cvs.width = window.innerWidth;
var cvs_h = cvs.height = window.innerHeight;
var cvs_wc = cvs_w / 2;
var cvs_hc = cvs_h / 2;
/* <---- General Settings */
/* Math Tools ----> */
var radians = function(angle) {
return (Math.PI / 180) * angle;
};
var percent_of = function(current, max) {
return (current / max) * 100;
};
var percent_from = function(percent) {
return 180 * (percent / 100);
};
/* <---- Math Tools */
var max_cd = 100;
var current_cd = 50;
var max_hp = 100;
var current_hp = 50;
/* Game Loop ----> */
var animate = function() {
ctx.clearRect(0, 0, cvs_w, cvs_h);
if(current_cd < max_cd) { current_cd += 0.5; } else { current_cd = 0; }
if(current_hp < max_hp) { current_hp += 0.5; } else { current_hp = 0; }
/* Cooldown UI */
var cd_percent = percent_of(current_cd, max_cd);
var angle_from_cd = percent_from(cd_percent);
ctx.beginPath();
ctx.moveTo(cvs_wc,cvs_hc);
ctx.arc(cvs_wc, cvs_hc, 15, radians(90), radians(90 + angle_from_cd));
ctx.lineTo(cvs_wc,cvs_hc);
ctx.strokeStyle = 'blue';
ctx.lineWidth = 3;
ctx.stroke();
ctx.fillStyle = 'lightblue';
ctx.fill();
/* Health UI */
var hp_percent = percent_of(current_hp, max_hp);
var angle_from_hp = percent_from(hp_percent);
ctx.beginPath();
ctx.moveTo(cvs_wc,cvs_hc);
ctx.arc(cvs_wc, cvs_hc, 15, radians(270), radians(270 + angle_from_hp));
ctx.lineTo(cvs_wc,cvs_hc);
ctx.strokeStyle = 'red';
ctx.lineWidth = 3;
ctx.stroke();
ctx.fillStyle = 'orange';
ctx.fill();
window.requestAnimationFrame(animate);
};
window.requestAnimationFrame(animate);
/* <---- Game Loop */
canvas {
position: absolute;
top: 0;
left: 0;
}
<canvas id="cvs"></canvas>
关于javascript - 绘制两个半圆,错误的填充点,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/36199107/