在畫布上繪制隨機彩色圓圈
[英]Draw random coloured circles on canvas
問題描述
我正在嘗試創建一個動畫，其中圓圈從右向左運行。 圓圈的顏色由功能隨機選擇。 我創造了一個小提琴 ，其中一個圓圈從右到左。 現在我的函數創建了一個隨機顏色。 此功能每秒執行一次，圓圈每秒更改一次顏色，而不是創建隨機拾取顏色的新圓圈。 如何更改它以便在畫布上每秒繪制一個新圓圈並且不僅會更改圓圈的顏色？
這是我的功能：
function getRandomElement(array) {
if (array.length == 0) {
return undefined;
}
return array[Math.floor(Math.random() * array.length)];
}
var circles = [
'#FFFF00',
'#FF0000',
'#0000FF'
];
function drawcircles() {
ctx.beginPath();
ctx.arc(ballx * 108, canvasHeight / 2, x*5, 0, 2*Math.PI, false);
ctx.fillStyle = getRandomElement(circles);
ctx.fill();
ctx.closePath;
}
1 個解決方案
解決方案1
1 已采納 2015-09-27 16:42:30
對您的問題的評論：
您正在將fillStyle的顏色更改為每幀的隨機顏色。 這就是它保持“改變”顏色的原因。 將其設置為圓的顏色：
context.fillStyle = circle.color;
- 使用數組制作具有x，y，直徑，彈力，速度和顏色的圓圈
- 使用requestAnimationFrame繪制並更新它們（我的是自定義函數）
我的答案：
我昨晚做了這個，其中一些圓圈跟隨光標並從屏幕邊緣“彈跳”。 我測試了代碼，它的工作原理。
我可能會在以后發布一個鏈接，但現在這里是所有代碼......
<!DOCTYPE html>
<html>
<body>
<canvas id="canvas"></canvas>
<script>
var lastTime = 0;
function requestMyAnimationFrame(callback, time)
{
var t = time || 16;
var currTime = new Date().getTime();
var timeToCall = Math.max(0, t - (currTime - lastTime));
var id = window.setTimeout(function(){ callback(currTime + timeToCall); }, timeToCall);
lastTime = currTime + timeToCall;
return id;
}
var canvas = document.getElementById("canvas");
var context = canvas.getContext("2d");
canvas.width = window.innerWidth - 20;
canvas.height = window.innerHeight - 20;
canvas.style.width = canvas.width + "px";
canvas.style.height = canvas.height + "px";
var circles = [];
var mouse =
{
x: 0,
y: 0
}
function getCoordinates(x, y)
{
return "(" + x + ", " + y + ")";
}
function getRatio(n, d)
{
// prevent division by 0
if (d === 0 || n === 0)
{
return 0;
}
else
{
return n/d;
}
}
function Circle(x,y,d,b,s,c)
{
this.x = x;
this.y = y;
this.diameter = Math.round(d);
this.radius = Math.round(d/2);
this.bounciness = b;
this.speed = s;
this.color = c;
this.deltaX = 0;
this.deltaY = 0;
this.drawnPosition = "";
this.fill = function()
{
context.beginPath();
context.arc(this.x+this.radius,this.y+this.radius,this.radius,0,Math.PI*2,false);
context.closePath();
context.fill();
}
this.clear = function()
{
context.fillStyle = "#ffffff";
this.fill();
}
this.draw = function()
{
if (this.drawnPosition !== getCoordinates(this.x, this.y))
{
context.fillStyle = this.color;
// if commented, the circle will be drawn if it is in the same position
//this.drawnPosition = getCoordinates(this.x, this.y);
this.fill();
}
}
this.keepInBounds = function()
{
if (this.x < 0)
{
this.x = 0;
this.deltaX *= -1 * this.bounciness;
}
else if (this.x + this.diameter > canvas.width)
{
this.x = canvas.width - this.diameter;
this.deltaX *= -1 * this.bounciness;
}
if (this.y < 0)
{
this.y = 0;
this.deltaY *= -1 * this.bounciness;
}
else if (this.y+this.diameter > canvas.height)
{
this.y = canvas.height - this.diameter;
this.deltaY *= -1 * this.bounciness;
}
}
this.followMouse = function()
{
// deltaX/deltaY will currently cause the circles to "orbit" around the cursor forever unless it hits a wall
var centerX = Math.round(this.x + this.radius);
var centerY = Math.round(this.y + this.radius);
if (centerX < mouse.x)
{
// circle is to the left of the mouse, so move the circle to the right
this.deltaX += this.speed;
}
else if (centerX > mouse.x)
{
// circle is to the right of the mouse, so move the circle to the left
this.deltaX -= this.speed;
}
else
{
//this.deltaX = 0;
}
if (centerY < mouse.y)
{
// circle is above the mouse, so move the circle downwards
this.deltaY += this.speed;
}
else if (centerY > mouse.y)
{
// circle is under the mouse, so move the circle upwards
this.deltaY -= this.speed;
}
else
{
//this.deltaY = 0;
}
this.x += this.deltaX;
this.y += this.deltaY;
this.x = Math.round(this.x);
this.y = Math.round(this.y);
}
}
function getRandomDecimal(min, max)
{
return Math.random() * (max-min) + min;
}
function getRoundedNum(min, max)
{
return Math.round(getRandomDecimal(min, max));
}
function getRandomColor()
{
// array of three colors
var colors = [];
// go through loop and add three integers between 0 and 255 (min and max color values)
for (var i = 0; i < 3; i++)
{
colors[i] = getRoundedNum(0, 255);
}
// return rgb value (RED, GREEN, BLUE)
return "rgb(" + colors[0] + "," + colors[1] + ", " + colors[2] + ")";
}
function createCircle(i)
{
// diameter of circle
var minDiameter = 25;
var maxDiameter = 50;
// bounciness of circle (changes speed if it hits a wall)
var minBounciness = 0.2;
var maxBounciness = 0.65;
// speed of circle (how fast it moves)
var minSpeed = 0.3;
var maxSpeed = 0.45;
// getRoundedNum returns a random integer and getRandomDecimal returns a random decimal
var x = getRoundedNum(0, canvas.width);
var y = getRoundedNum(0, canvas.height);
var d = getRoundedNum(minDiameter, maxDiameter);
var c = getRandomColor();
var b = getRandomDecimal(minBounciness, maxBounciness);
var s = getRandomDecimal(minSpeed, maxSpeed);
// create the circle with x, y, diameter, bounciness, speed, and color
circles[i] = new Circle(x,y,d,b,s,c);
}
function makeCircles()
{
var maxCircles = getRoundedNum(2, 5);
for (var i = 0; i < maxCircles; i++)
{
createCircle(i);
}
}
function drawCircles()
{
var ii = 0;
for (var i = 0; ii < circles.length; i++)
{
if (circles[i])
{
circles[i].draw();
ii++;
}
}
}
function clearCircles()
{
var ii = 0;
for (var i = 0; ii < circles.length; i++)
{
if (circles[i])
{
circles[i].clear();
ii++;
}
}
}
function updateCircles()
{
var ii = 0;
for (var i = 0; ii < circles.length; i++)
{
if (circles[i])
{
circles[i].keepInBounds();
circles[i].followMouse();
ii++;
}
}
}
function update()
{
requestMyAnimationFrame(update,10);
updateCircles();
}
function draw()
{
requestMyAnimationFrame(draw,1000/60);
context.clearRect(0,0,canvas.width,canvas.height);
drawCircles();
}
function handleError(e)
{
//e.preventDefault();
//console.error(" ERROR ------ " + e.message + " ------ ERROR ");
}
window.addEventListener("load", function()
{
window.addEventListener("error", function(e)
{
handleError(e);
});
window.addEventListener("resize", function()
{
canvas.width = window.innerWidth - 20;
canvas.height = window.innerHeight - 20;
});
window.addEventListener("mousemove", function(e)
{
mouse.x = e.layerX || e.offsetX;
mouse.y = e.layerY || e.offsetY;
});
makeCircles();
update();
draw();
});
</script>
</body>
</html>
用js在html畫布上繪制隨機彩色圓圈？
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