Canvas动画转视频-前段框架whammy

叁歲伎倆 2024-04-17 22:19 55阅读 0赞

# Canvas动画转视频-前段框架whammy #

> whammy是在前端将canvas动画转视频，它的github地址为：https://github.com/antimatter15/whammy  
> 由于英文比较晦涩难懂，接下来就实践一下体会whammy的用法。

## 写一个时钟动画 ##

我直接在官网的demo基础上改了一些。

<canvas id="canvas" width="150" height="150"></canvas>
    <script>
        
        function clock(time){
            var now = new Date();
            now.setTime(time);
            var ctx = document.getElementById('canvas').getContext('2d');
            ctx.save();
            ctx.fillStyle = 'white'
            ctx.fillRect(0,0,150,150); // videos cant handle transprency
            ctx.translate(75,75);
            ctx.scale(0.4,0.4);
            ctx.rotate(-Math.PI/2);
            ctx.strokeStyle = "black";
            ctx.fillStyle = "white";
            ctx.lineWidth = 8;
            ctx.lineCap = "round";
            
            // Hour marks
            ctx.save();
            for (var i=0;i<12;i++){
                ctx.beginPath();
                ctx.rotate(Math.PI/6);
                ctx.moveTo(100,0);
                ctx.lineTo(120,0);
                ctx.stroke();
            }
            ctx.restore();
            
            // Minute marks
            ctx.save();
            ctx.lineWidth = 5;
            for (i=0;i<60;i++){
                if (i%5!=0) {
                    ctx.beginPath();
                    ctx.moveTo(117,0);
                    ctx.lineTo(120,0);
                    ctx.stroke();
                }
                ctx.rotate(Math.PI/30);
            }
            ctx.restore();
            
            var sec = now.getSeconds();
            var min = now.getMinutes();
            var hr  = now.getHours();
            hr = hr>=12 ? hr-12 : hr;
            
            ctx.fillStyle = "black";
            
            // write Hours
            ctx.save();
            ctx.rotate( hr*(Math.PI/6) + (Math.PI/360)*min + (Math.PI/21600)*sec )
            ctx.lineWidth = 14;
            ctx.beginPath();
            ctx.moveTo(-20,0);
            ctx.lineTo(80,0);
            ctx.stroke();
            ctx.restore();
            
            // write Minutes
            ctx.save();
            ctx.rotate( (Math.PI/30)*min + (Math.PI/1800)*sec )
            ctx.lineWidth = 10;
            ctx.beginPath();
            ctx.moveTo(-28,0);
            ctx.lineTo(112,0);
            ctx.stroke();
            ctx.restore();
            
            // Write seconds
            ctx.save();
            ctx.rotate(sec * Math.PI/30);
            ctx.strokeStyle = "#D40000";
            ctx.fillStyle = "#D40000";
            ctx.lineWidth = 6;
            ctx.beginPath();
            ctx.moveTo(-30,0);
            ctx.lineTo(83,0);
            ctx.stroke();
            ctx.beginPath();
            ctx.arc(0,0,10,0,Math.PI*2,true);
            ctx.fill();
            ctx.beginPath();
            ctx.arc(95,0,10,0,Math.PI*2,true);
            ctx.stroke();
            ctx.fillStyle = "#555";
            ctx.arc(0,0,3,0,Math.PI*2,true);
            ctx.fill();
            ctx.restore();
            
            ctx.beginPath();
            ctx.lineWidth = 14;
            ctx.strokeStyle = '#325FA2';
            ctx.arc(0,0,142,0,Math.PI*2,true);
            ctx.stroke();
            
            ctx.restore();
            
            return ctx;
        }
    
    var last_time = +new Date;
    
    
    var progress = 1;
    
    function next(){
        progress++;
        clock(last_time += 1000);
        if(progress<100){
    
    
    -->
    
    
    
    
    requestAnimationFrame(next);
        }else{
          
        }
    }
    
    next();
        
    </script>

## 如何转视频 ##

1.  引入whammy.js的库，下载whammy.js，路径需要在同一级。 `<script src="whammy.js"></script>`
2.  引入Whammy的viedo对象 `var video = new Whammy.Video(15);`
3.  每一个画布对象添加进来 `video.add(context);`
4.  动画结束时生成视频，交给框架`requestAnimationFrame(finalizeVideo);`

完整代码如下

<canvas id="canvas" width="150" height="150"></canvas>
    <a style="display:none" id="download" download="clock.webm">Download video</a>
    <script src="whammy.js"></script>
    
    <script>
        
        function clock(time){
            var now = new Date();
            now.setTime(time);
            var ctx = document.getElementById('canvas').getContext('2d');
            ctx.save();
            ctx.fillStyle = 'white'
            ctx.fillRect(0,0,150,150); // videos cant handle transprency
            ctx.translate(75,75);
            ctx.scale(0.4,0.4);
            ctx.rotate(-Math.PI/2);
            ctx.strokeStyle = "black";
            ctx.fillStyle = "white";
            ctx.lineWidth = 8;
            ctx.lineCap = "round";
            
            // Hour marks
            ctx.save();
            for (var i=0;i<12;i++){
                ctx.beginPath();
                ctx.rotate(Math.PI/6);
                ctx.moveTo(100,0);
                ctx.lineTo(120,0);
                ctx.stroke();
            }
            ctx.restore();
            
            // Minute marks
            ctx.save();
            ctx.lineWidth = 5;
            for (i=0;i<60;i++){
                if (i%5!=0) {
                    ctx.beginPath();
                    ctx.moveTo(117,0);
                    ctx.lineTo(120,0);
                    ctx.stroke();
                }
                ctx.rotate(Math.PI/30);
            }
            ctx.restore();
            
            var sec = now.getSeconds();
            var min = now.getMinutes();
            var hr  = now.getHours();
            hr = hr>=12 ? hr-12 : hr;
            
            ctx.fillStyle = "black";
            
            // write Hours
            ctx.save();
            ctx.rotate( hr*(Math.PI/6) + (Math.PI/360)*min + (Math.PI/21600)*sec )
            ctx.lineWidth = 14;
            ctx.beginPath();
            ctx.moveTo(-20,0);
            ctx.lineTo(80,0);
            ctx.stroke();
            ctx.restore();
            
            // write Minutes
            ctx.save();
            ctx.rotate( (Math.PI/30)*min + (Math.PI/1800)*sec )
            ctx.lineWidth = 10;
            ctx.beginPath();
            ctx.moveTo(-28,0);
            ctx.lineTo(112,0);
            ctx.stroke();
            ctx.restore();
            
            // Write seconds
            ctx.save();
            ctx.rotate(sec * Math.PI/30);
            ctx.strokeStyle = "#D40000";
            ctx.fillStyle = "#D40000";
            ctx.lineWidth = 6;
            ctx.beginPath();
            ctx.moveTo(-30,0);
            ctx.lineTo(83,0);
            ctx.stroke();
            ctx.beginPath();
            ctx.arc(0,0,10,0,Math.PI*2,true);
            ctx.fill();
            ctx.beginPath();
            ctx.arc(95,0,10,0,Math.PI*2,true);
            ctx.stroke();
            ctx.fillStyle = "#555";
            ctx.arc(0,0,3,0,Math.PI*2,true);
            ctx.fill();
            ctx.restore();
            
            ctx.beginPath();
            ctx.lineWidth = 14;
            ctx.strokeStyle = '#325FA2';
            ctx.arc(0,0,142,0,Math.PI*2,true);
            ctx.stroke();
            
            ctx.restore();
            
            return ctx;
        }
    
    
    var video = new Whammy.Video(15);
    
    var last_time = +new Date;
    
    var progress = 1;
    
    function next(){
        progress++;
        var context = clock(last_time += 1000);
    
        video.add(context);
        if(progress<100){
    
    
    -->
    
    
    
    
    requestAnimationFrame(next);
        }else{
    
          requestAnimationFrame(finalizeVideo);
        }
    }
    
    function finalizeVideo(){
        var start_time = +new Date;
        video.compile(false, function(output){
                      
                      var end_time = +new Date;
                      var url = webkitURL.createObjectURL(output);
                      console.log("url:"+url);
                      document.getElementById('download').style.display = '';
                      document.getElementById('download').href = url;
                      });
    }
    
    next();
        
    </script>