Use Canvas to imitate the method of loading small balls on Baidu Tieba client-H5 Tutorial-php.cn

Use Canvas to imitate the method of loading small balls on Baidu Tieba client

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Release： 2018-07-03 10:50:29

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This article mainly introduces to you the implementation method of using Canvas to imitate Baidu Tieba client loading ball. The correlation after implementation is very similar. The article gives detailed sample code for your reference and study, which has certain benefits for everyone. It has reference value. Friends who need it can come and study together.

Preface

I recently saw two interesting demos, the renderings are as follows:

Today I took advantage of the free time on the weekend and imitated it using H5 Canvas. This article only implements the first rendering.

This is the effect I achieved:

Principle of implementation

The implementation principle is based on the article in the brief book and will not be repeated here. Now let's achieve this effect step by step.

Step 0: Draw a circle

The source code is as follows:

The running effect is as follows:

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>百度贴吧客户端Loading小球</title>
    <style>
        canvas {
            border: 1px solid #ccc;
        }
    </style>
</head>
<body>
<canvas id="canvas" width="500" height="500"></canvas>
<script>
    var canvas = document.getElementById(&#39;canvas&#39;)
    var ctx = canvas.getContext(&#39;2d&#39;)
    canvas.width = 500
    canvas.height = 500

    var grid = canvas.width / 4
    var cx = canvas.width / 2 // 圆中心点 x 坐标
    var cy = canvas.height / 2 // 圆中心点 y 坐标

    function circle() {
        ctx.beginPath()
        ctx.arc(cx, cy, grid / 2, 0, 2 * Math.PI)
    }

    circle()
    ctx.stroke()
</script>
</body>
</html>

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This demo only involves the simplest usage of Canvas.

Step 1: Draw the blue word "Post"

Use ctx.fillText to draw a blue in the center of the circle The word "post". Text is bold and centered horizontally.

The code is as follows:

function text(fillStyle) {
    var fontSize = size / 250 * 120
    ctx.font = &#39;bold &#39; + fontSize + &#39;px Arial&#39;
    ctx.textAlign = &#39;center&#39;
    ctx.fillStyle = fillStyle
    ctx.fillText(&#39;贴&#39;, cx, cy + fontSize * 0.3)
}

text(&#39;#29a3fe&#39;)

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The effect is as follows:

Step 2: Draw blue waves

var waveSize = size / 6 // 波浪大小
var x = 0 // 波浪位置偏移大小

function curve() {
    ctx.beginPath()
    ctx.moveTo(cx - size + x + size / 2, cy)
    ctx.quadraticCurveTo(cx - size + size / 4 + x + size / 2, cy - waveSize, cx - size + size / 2 + x + size / 2, cy)
    ctx.quadraticCurveTo(cx - size + size * 3 / 4 + x + size / 2, cy + waveSize, cx - size + size + x + size / 2, cy)

    ctx.quadraticCurveTo(cx + size / 4 + x + size / 2, cy - waveSize, cx + size / 2 + x + size / 2, cy)
    ctx.quadraticCurveTo(cx + size * 3 / 4 + x + size / 2, cy + waveSize, cx + size + x + size / 2, cy)
    ctx.lineTo(cx + size + x + size / 2, canvas.height)
    ctx.lineTo(cx - size + x + size / 2, canvas.height)
    ctx.lineTo(cx - size + x + size / 2, cy)
    ctx.closePath()
}

ctx.fillStyle = &#39;#29a3fe&#39;
curve()
ctx.fill()

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The effect is as follows:

# #Step 3: Draw the white word "sticker"

curve()
ctx.clip()
text(&#39;#f00&#39;)

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The first sentence of code

curve() creates a The difference between the wavy path and the third step is that ctx.fill() is not used to fill the path, but ctx.clip() is used to clip the path, so If so, the path drawn later (including text) can only be displayed within the clipping area.

In order to distinguish it from the background color, I changed the word "post" to red.

The effect is as follows:

Step 4: Draw moving waves

function loop(){
    ctx.clearRect(0, 0, canvas.width, canvas.height)

    x -= 1.5
    x = x % size

    ctx.save()

    circle()
    ctx.stroke()
 
    ctx.fillStyle = &#39;#29a3fe&#39;
    curve()
    ctx.fill()

    ctx.restore()

    requestAnimationFrame(loop)
}
loop()

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The effect is as follows:

Step 5: Integrate the previous content

The effect is as follows:

Step 6: Cut the circle

Put the step 0:

circle()
ctx.stroke()

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Change to:

circle()
ctx.clip()

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This way you can cut out the outer shape of the circle, and then you're done.

Finally, the complete source code is attached:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        html,
        body {
            height: 100%;
        }
        canvas {
            border: 1px solid #ccc;
        }
    </style>
</head>
<body>
<canvas id="canvas" width="500" height="500"></canvas>
<script>
    var canvas = document.getElementById(&#39;canvas&#39;)
    var ctx = canvas.getContext(&#39;2d&#39;)
    canvas.width = 500
    canvas.height = 500

    var size = canvas.width / 4 // 圆的大小
    var cx = canvas.width / 2 // 圆中心点 x 坐标
    var cy = canvas.height / 2 // 圆中心点 y 坐标
    var waveSize = size / 6 // 波浪大小
    var x = 0 // 波浪位置偏移大小

    function circle() {
        ctx.beginPath()
        ctx.arc(cx, cy, size / 2, 0, 2 * Math.PI)
    }

    function curve() {
        ctx.beginPath()
        ctx.moveTo(cx - size + x + size / 2, cy)
        ctx.quadraticCurveTo(cx - size + size / 4 + x + size / 2, cy - waveSize, cx - size + size / 2 + x + size / 2, cy)
        ctx.quadraticCurveTo(cx - size + size * 3 / 4 + x + size / 2, cy + waveSize, cx - size + size + x + size / 2, cy)

        ctx.quadraticCurveTo(cx + size / 4 + x + size / 2, cy - waveSize, cx + size / 2 + x + size / 2, cy)
        ctx.quadraticCurveTo(cx + size * 3 / 4 + x + size / 2, cy + waveSize, cx + size + x + size / 2, cy)
        ctx.lineTo(cx + size + x + size / 2, canvas.height)
        ctx.lineTo(cx - size + x + size / 2, canvas.height)
        ctx.lineTo(cx - size + x + size / 2, cy)
        ctx.closePath()
    }

    function text(fillStyle) {
        var fontSize = size / 250 * 120
        ctx.font = &#39;bold &#39; + fontSize + &#39;px Arial&#39;
        ctx.textAlign = &#39;center&#39;
        ctx.fillStyle = fillStyle
        ctx.fillText(&#39;贴&#39;, cx, cy + fontSize * 0.3)
    }

    function loop(){
        ctx.clearRect(0, 0, canvas.width, canvas.height)

        x -= 1.5
        x = x % size

        ctx.save()

        circle()
        ctx.clip()

        text(&#39;#29a3fe&#39;)

        ctx.fillStyle = &#39;#29a3fe&#39;
        curve()
        ctx.fill()

        curve()
        ctx.clip()

        text(&#39;#fff&#39;)

        ctx.restore()

        requestAnimationFrame(loop)
    }
    loop()
</script>
</body>
</html>

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