javascript - 尝试在 html5 中创建五彩纸屑效果，如何为每个元素获得不同的填充颜色？

Question

编辑:

对于任何好奇的人，这是最终结果。

http://jsfiddle.net/Javalsu/vxP5q/743/embedded/result/

---

我正在构建我在此链接中找到的代码

http://thecodeplayer.com/walkthrough/html5-canvas-snow-effect

我想让它更像是五彩纸屑掉落的效果，而不是雪花效果，我需要为每个元素制作不同的颜色。但似乎一次性为整个 Canvas 设置了填充颜色。

有没有办法为每个元素指定不同的填充颜色，或者我是否以完全错误的方式进行处理？

谢谢

更新:如果有人需要五彩纸屑，这是成品

http://jsfiddle.net/mj3SM/6/

window.onload = function () {
//canvas init
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");

//canvas dimensions
var W = window.innerWidth;
var H = window.innerHeight;
canvas.width = W;
canvas.height = H;

//snowflake particles
var mp = 200; //max particles
var particles = [];
for (var i = 0; i < mp; i++) {
    particles.push({
        x: Math.random() * W, //x-coordinate
        y: Math.random() * H, //y-coordinate
        r: Math.random() * 15 + 1, //radius
        d: Math.random() * mp, //density
        color: "rgba(" + Math.floor((Math.random() * 255)) + ", " + Math.floor((Math.random() * 255)) + ", " + Math.floor((Math.random() * 255)) + ", 0.8)",
        tilt: Math.floor(Math.random() * 5) - 5
    });
}

//Lets draw the flakes
function draw() {
    ctx.clearRect(0, 0, W, H);



    for (var i = 0; i < mp; i++) {
        var p = particles[i];
        ctx.beginPath();
        ctx.lineWidth = p.r;
        ctx.strokeStyle = p.color; // Green path
        ctx.moveTo(p.x, p.y);
        ctx.lineTo(p.x + p.tilt + p.r / 2, p.y + p.tilt);
        ctx.stroke(); // Draw it
    }

    update();
}

//Function to move the snowflakes
//angle will be an ongoing incremental flag. Sin and Cos functions will be applied to it to create vertical and horizontal movements of the flakes
var angle = 0;

function update() {
    angle += 0.01;
    for (var i = 0; i < mp; i++) {
        var p = particles[i];
        //Updating X and Y coordinates
        //We will add 1 to the cos function to prevent negative values which will lead flakes to move upwards
        //Every particle has its own density which can be used to make the downward movement different for each flake
        //Lets make it more random by adding in the radius
        p.y += Math.cos(angle + p.d) + 1 + p.r / 2;
        p.x += Math.sin(angle) * 2;

        //Sending flakes back from the top when it exits
        //Lets make it a bit more organic and let flakes enter from the left and right also.
        if (p.x > W + 5 || p.x < -5 || p.y > H) {
            if (i % 3 > 0) //66.67% of the flakes
            {
                particles[i] = {
                    x: Math.random() * W,
                    y: -10,
                    r: p.r,
                    d: p.d,
                    color: p.color,
                    tilt: p.tilt
                };
            } else {
                //If the flake is exitting from the right
                if (Math.sin(angle) > 0) {
                    //Enter from the left
                    particles[i] = {
                        x: -5,
                        y: Math.random() * H,
                        r: p.r,
                        d: p.d,
                        color: p.color,
                        tilt: p.tilt
                    };
                } else {
                    //Enter from the right
                    particles[i] = {
                        x: W + 5,
                        y: Math.random() * H,
                        r: p.r,
                        d: p.d,
                        color: p.color,
                        tilt: p.tilt
                    };
                }
            }
        }
    }
}

//animation loop
setInterval(draw, 20);

Answer 1

像这样尝试:http://jsfiddle.net/vxP5q/

JS:

window.onload = function(){
//canvas init
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");

//canvas dimensions
var W = window.innerWidth;
var H = window.innerHeight;
canvas.width = W;
canvas.height = H;

//snowflake particles
var mp = 25; //max particles
var particles = [];
for(var i = 0; i < mp; i++)
{
    particles.push({
        x: Math.random()*W, //x-coordinate
        y: Math.random()*H, //y-coordinate
        r: Math.random()*4+1, //radius
        d: Math.random()*mp, //density
        color: "rgba(" + Math.floor((Math.random() * 255)) +", " + Math.floor((Math.random() * 255)) +", " + Math.floor((Math.random() * 255)) + ", 0.8)"
    })
}

//Lets draw the flakes
function draw()
{
    ctx.clearRect(0, 0, W, H);



    for(var i = 0; i < mp; i++)
    { 
        var p = particles[i];
        ctx.beginPath();
        ctx.fillStyle = p.color;
        ctx.moveTo(p.x, p.y);
        ctx.arc(p.x, p.y, p.r, 0, Math.PI*2, true);
        ctx.fill();
    }

    update();
}

//Function to move the snowflakes
//angle will be an ongoing incremental flag. Sin and Cos functions will be applied to it to create vertical and horizontal movements of the flakes
var angle = 0;
function update()
{
    angle += 0.01;
    for(var i = 0; i < mp; i++)
    {
        var p = particles[i];
        //Updating X and Y coordinates
        //We will add 1 to the cos function to prevent negative values which will lead flakes to move upwards
        //Every particle has its own density which can be used to make the downward movement different for each flake
        //Lets make it more random by adding in the radius
        p.y += Math.cos(angle+p.d) + 1 + p.r/2;
        p.x += Math.sin(angle) * 2;

        //Sending flakes back from the top when it exits
        //Lets make it a bit more organic and let flakes enter from the left and right also.
        if(p.x > W+5 || p.x < -5 || p.y > H)
        {
            if(i%3 > 0) //66.67% of the flakes
            {
                particles[i] = {x: Math.random()*W, y: -10, r: p.r, d: p.d, color : p.color};
            }
            else
            {
                //If the flake is exitting from the right
                if(Math.sin(angle) > 0)
                {
                    //Enter from the left
                    particles[i] = {x: -5, y: Math.random()*H, r: p.r, d: p.d, color: p.color};
                }
                else
                {
                    //Enter from the right
                    particles[i] = {x: W+5, y: Math.random()*H, r: p.r, d: p.d, color : p.color};
                }
            }
        }
    }
}

//animation loop
setInterval(draw, 33);
}

我做了什么。在生成像素的地方，我添加了一种独特的(随机)颜色。在更新的地方，我确保颜色已更改，并且我已更改它的绘制位置，以便它会为每个五彩纸屑项目创建一个独特的路径。