用H5的canvas做恐怖动画-木庄网络博客

本文摘自PHP中文网，作者php中世界最好的语言，侵删。

这次给大家带来用H5的canvas做恐怖动画，用H5的canvas做恐怖动画的注意事项有哪些，下面就是实战案例，一起来看一下。

canvas可以实现一些有趣的效果，动画实现。以一个简单的页面实现了解一下基础的画图方法。

效果

万圣节快乐

预备知识

1	`let canvas = document.getElementById('canvas');let context = canvas.getContext('2d');`

开始路径

1	`context.beginPath();`

beginPath()方法在画布上开始一条绘制路径，或重置当前的路径。

移动路径

1	`context.moveTo();`

moveTo()方法把路径移动到画布中指定点，不创建线条。

添加线条

1	`context.lineTo();`

lineTo()方法添加一个新点，在画布中创建该点到指定点的线条。

画图drawImage

1	`context.drawImage(image,x,y);`

drawImage()方法可以在画布上绘制图像、画布或视频，也可以绘制图像的某些部分，增加／减少图像的尺寸。

获取像素数据

1	`context.getImageData(x,y,width,height);`

getImageData()方法可以获取画布imageData对象，该对象指定了矩形的像素数据。

在imageData对象中每个像素都存在rgba值，以数组形式存储在data属性中。

放回像素数据

1	`context.putImageData(imageData,x,y);`

putImageData()方法将获取的图像数据放回到画布上。

实现

html

1	`<canvas id="canvas"></canvas><button id="click"` `class="switch">Click</button>`

css

html,body,canvas {    width: 100%;    height: 100%;    margin: 0;
}.switch {    position: absolute;    top: 70%;    right: 10%;    width: 50px;    height: 50px;    border-radius: 50px;    outline: none;    cursor: pointer;    animation: switch-animate alternate infinite ease 1s 0s;
}
@keyframes switch-animate {    from {        box-shadow: 0 0 30px #ece9c5;
    }    to {        box-shadow: 0 0 100px #eae5a7;
    }
}

(function () {    class Halloween {        constructor(id) {            this.canvas = document.getElementById(id);            this.ctx = this.canvas.getContext('2d');            this.w = this.canvas.width;            this.h = this.canvas.height;            this.data = [];
        }        //初始画布
        initDraw(img) {            this.w = this.canvas.width = img.width;            this.h = this.canvas.height = img.height;            this.ctx.drawImage(img, 0, 0);            this.data = this.ctx.getImageData(0, 0, this.w, this.h);
        }        //显示文字
        drawText() {            this.ctx.font = '60px Verdana';            this.ctx.fillStyle = '#ffffff';            this.ctx.fillText('万圣节快乐', 350, 280);
        }        //闪电
        lightning() {            let ctx = this.ctx;
            ctx.strokeStyle = '#fff';
            ctx.lineWidth = 2;
            ctx.beginPath();
            ctx.moveTo(800, 10);
            ctx.lineTo(600, 100);
            ctx.lineTo(500, 200);
            ctx.stroke();
            ctx.beginPath();
            ctx.moveTo(600, 100);
            ctx.lineTo(650, 170);
            ctx.stroke()
        }        //打雷
        thunder() {            let timer = Math.floor(800 * Math.random());            this.reverse();            this.lightning();            this.drawText();
            setTimeout(() => {                this.reset();
            }, timer);
        }        //反转画布
        reverse() {            let imgData = this.ctx.getImageData(0, 0, this.w, this.h);            for (var i = 0, len = imgData.data.length; i < len; i += 4) {
                imgData.data[i] = 255 - imgData.data[i];
                imgData.data[i + 1] = 255 - imgData.data[i + 1];
                imgData.data[i + 2] = 255 - imgData.data[i + 2];
                imgData.data[i + 3] = 255;
            }            this.ctx.putImageData(imgData, 0, 0);
        }        //重置画布
        reset() {            this.ctx.putImageData(this.data, 0, 0);
        }
    }    let halloween = new Halloween('canvas');    let canvas = document.getElementById('canvas');    let ctx = canvas.getContext('2d');    let img = new Image();
    img.src = '/images/halloween.png';
    img.onload = () => {
        halloween.initDraw(img);
    }    document.getElementById('click').onclick = () => {
        halloween.thunder();
    }
})();