如何用动画帆布曲线的绘制？(How to animate the drawing of a Curv

我有一大堆，我想慢慢地画点的。 我尝试setTimeout和从这个效果教程 。 但是，如果没有这么多的成功。

该功能看起来是这样的

功能：

var myFunction = function(ctx, grid, points) {
                ctx.beginPath();
                ctx.moveTo(points[0].x, points[0].y);
                ctx.lineWidth = 2;
                ctx.strokeStyle = '#2068A8';
                ctx.fillStyle = '#2068A8';
                var count = 1;
                for (count = 1; count < points.length; count++) {
                    ctx.lineTo(points[count].x , points[count].y);
                }
                ctx.stroke();
            }

围绕着这个功能有一个很多其他的绘图功能，但我只是想只有一个动画。

我怎样才能慢慢画与油画的功能？

Answer 1:

有两种方法可以去这样做，我能想到的把我的头顶部。 一个基本上是绘制点和绘制其他点之前暂停一定量的时间。 这是第一个例子中，我provided.The第二种方法涉及绘制局部线到当前的目标，这获得了更平滑的图的外观。 作为一个方面说明我使用requestAnimationFrame在这两个例子中，其推荐的方法做任何类型的帆布动画。

var canvas = document.getElementById("canvas"),
    ctx = canvas.getContext("2d");

canvas.width = 400;
canvas.height = 200;

var points = [],
    currentPoint = 1,
    nextTime = new Date().getTime()+500,
    pace = 200;

// make some points
for (var i = 0; i < 50; i++) {
    points.push({
        x: i * (canvas.width/50),
        y: 100+Math.sin(i) * 10
    });
}

function draw() {

    if(new Date().getTime() > nextTime){
        nextTime = new Date().getTime() + pace;

        currentPoint++;
        if(currentPoint > points.length){
            currentPoint = 0;
        }
    }
    ctx.clearRect(0,0,canvas.width, canvas.height);
    ctx.beginPath();
    ctx.moveTo(points[0].x, points[0].y);
    ctx.lineWidth = 2;
    ctx.strokeStyle = '#2068A8';
    ctx.fillStyle = '#2068A8';
    for (var p = 1, plen = currentPoint; p < plen; p++) {
        ctx.lineTo(points[p].x, points[p].y);
    }
    ctx.stroke();

    requestAnimFrame(draw);
}

draw();

现场演示

如果您发现是有些不连贯，你可以做的就是正在绘制线条更加流畅以下

var canvas = document.getElementById("canvas"),
    ctx = canvas.getContext("2d");

canvas.width = 400;
canvas.height = 200;

var points = [],
    currentPoint = 1,
    speed = 2,
    targetX = 0,
    targetY = 0,
    x = 0,
    y = 0;

// make some points
for (var i = 0; i < 50; i++) {
    points.push({
        x: i * (canvas.width/50),
        y: 100+Math.sin(i) * 10
    });
}

// set the initial target and starting point
targetX = points[1].x;
targetY = points[1].y;
x = points[0].x;
y = points[0].y;

function draw() {
    var tx = targetX - x,
        ty = targetY - y,
        dist = Math.sqrt(tx*tx+ty*ty),
        velX = (tx/dist)*speed,
        velY = (ty/dist)*speed;

        x += velX
        y += velY;

    if(dist < 1){
        currentPoint++;

        if(currentPoint >= points.length){
            currentPoint = 1;
            x = points[0].x;
            y = points[0].y;
        }

        targetX = points[currentPoint].x;
        targetY = points[currentPoint].y;
    }

    ctx.clearRect(0,0,canvas.width, canvas.height);
    ctx.beginPath();
    ctx.moveTo(points[0].x, points[0].y);
    ctx.lineWidth = 2;
    ctx.strokeStyle = '#2068A8';
    ctx.fillStyle = '#2068A8';

    for (var p = 0, plen = currentPoint-1; p < plen; p++) {
        ctx.lineTo(points[p].x, points[p].y);
    }
    ctx.lineTo(x, y);    
    ctx.stroke();

    requestAnimFrame(draw);
}

draw();

现场演示

文章来源: How to animate the drawing of a Curve with Canvas?