HTML5 Canvas动画使用88-98％的CPU [英] HTML5 Canvas animation uses 88-98% of CPU

查看：1641 发布时间：2016/11/13 3:42:48 canvas cpu-usage html5-animation

本文介绍了HTML5 Canvas动画使用88-98％的CPU的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

我试图动画一个人造像素化的世界地图，使它在不同颜色之间平滑过渡。我最初使用jquery和表，但cpu使用是非常高，所以我想我会尝试html5画布。然而，我仍然得到非常高的cpu使用这个。我想知道如果它的大数组在代码（我用来指示一个正方形应填充）。任何帮助将深深赞赏。

i'm trying to animate a faux pixelated map of the world so that it transitions between different colors smoothly. i originially did this with jquery and tables but the cpu usage was very high so i thought i'd try html5 canvas instead. However, i still get very high cpu usage for this. i'm wondering if its the large array in the code (which i use to indicate where a square should be filled). any help would be deeply appreciated.

<!DOCTYPE html>
<html>
<head>
    <title>canvas version</title>
    <script src="raphael.js"></script>
    <script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/1.4.4/jquery.min.js"></script>
</head>
<body>
<div id="canvasesdiv" style="position:relative; width:864px; height:456px">
    <canvas id="world-map" width="864" height="456" style="position:absolute; left:0px; top:0px; z-index:1;">
    </canvas>
    <canvas id="backdrop" width="864" height="456" style="position:absolute; left:0px; top:0px; z-index:0;"></canvas>
    <script type="text/javascript">
        //declare vars
        var ctx1
        var ctx2
        var layer1
        var layer2
        var red = 255;
        var dr = 1;
        //initialization
        function init() {
            layer1 = document.getElementById("backdrop");
            ctx1 = layer1.getContext("2d");
            //layer2 = document.getElementById("world-map");
            //ctx2 = layer2.getContext("2d");
            drawMap(red);
            setInterval(function(){red = drawMap(red);},1);
            }

            //LOOP THROUGH THE ARRAY IT SHOULD BE 38 ROWS EACH WITH 72 COLUMN ENTRIES make each one 12x12 and then fill according to array non zero entries
        var array = [[0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0], [0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 21.0, 22.0, 0.0, 0.0, 25.0, 26.0, 27.0, 28.0, 29.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0], [0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 18.0, 19.0, 20.0, 21.0, 22.0, 23.0, 24.0, 25.0, 26.0, 27.0, 28.0, 29.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 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            //Draw the map and animate the background in red only for now
        function drawMap(){
            ctx1.clearRect(0,0, 864, 456);
            red -= dr
            if (red < 0 || red > 255){
                dr = -dr
            }
            ctx1.fillStyle = 'rgb('+red+',0,0)';
            ctx1.strokeStyle = '#000';
            for (var row = 0; row < 38; row+=1){
                for (var col = 0; col < 72; col+=1){
                    if (array[row][col] != 0.0){
                        ctx1.fillRect(col*12,row*12,12,12);
                        ctx1.strokeRect(col*12,row*12,12,12);
                    }
                }
            }
            return red;
        }
    init();  
    </script>
    </div>
</body>
</html>

推荐答案

以下是我如何修改代码。主要更改：

Here's how I would modify your code. Major changes:

不要尽快调用 drawMap

预计算xy偏移，跳过零，只有一次。这显着缩短了在 drawMap 中循环的迭代次数。（〜970 vs.〜2700）

使用事实 drawMap 是一个闭包来修改 / code>直接而不需要返回/分配。

 
 删除 12 的硬编码，您可以在一个地方设置 squareSize ，并相应地更新您的代码和画布。
 
 将每个框架的偏移量更改为 5 而不是 1 实际上，最好的选择是指定一个redPerSecond变量，并计算 drawMap 调用之间的帧间延迟，使得颜色脉冲以相同的世界速度发生，而不管
 
 从地图数组中删除所有小数，以缩短代码，并引入合理的换行符，以便我的文本编辑器不会哭泣。
 
 否需要将 strokeStyle 设置为相同的值，每次调用 drawMap（）。



Do not call drawMap as fast as possible, instead maxing out at 30fps (and in practice slightly less).
Precalculate the xy offsets, skipping zeroes, once only. This significantly shortens the number of iterations you loop through in drawMap. (~970 vs. ~2700)
Use the fact that drawMap is a closure to modify red directly with no need to return/assign it.
Remove the hard-coding of 12, instead letting you set squareSize in one spot and have your code and canvas updated accordingly.
Change the offset per 'frame' to 5 instead of 1 to account for lower fps. In reality, the best choice would be to specify a redPerSecond variable and calculate the inter-frame delay between calls to drawMap so that the color pulsing happens at the same world speed regardless of framerate.
Remove all decimals from your map array for shorter code, and introduce reasonable linebreaks so that my text editor doesn't cry.
No need to set the strokeStyle to the same value each call to drawMap().

 
 
 
  var map = [
    [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0],
    [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,21,22,0,0,25,26,27,28,29,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0],
    [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,18,19,20,21,22,23,24,25,26,27,28,29,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0],
    [0,0,0,0,0,0,0,0,0,0,0,0,12,13,14,15,16,17,18,19,0,0,22,23,24,25,26,27,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,44,45,46,47,48,49,50,0,0,53,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0],
    [0,0,0,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,0,22,23,24,25,26,0,0,0,0,0,0,33,34,35,36,37,0,0,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,0,0,0,0,0,0,0,0,0,0,0],
    [0,0,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,0,0,22,23,0,0,0,27,28,0,0,0,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,0,0,0,0,0,0,0,0,0],
    [0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,0,0,0,0,0,0,0,0,0,0,0,0,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,0,0,0,0,0,0,0,0,0,0,0],
    [0,1,2,0,0,0,6,7,8,9,10,11,12,13,14,15,16,17,18,19,0,0,0,0,0,0,0,0,0,0,30,0,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,0,0,0,60,0,0,0,0,0,0,0,0,0,0,0],
    [0,0,0,0,0,0,6,7,8,9,10,11,12,13,14,15,16,17,18,19,0,0,0,0,0,0,0,0,0,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,0,0,60,0,0,0,0,0,0,0,0,0,0,0],
    [0,0,0,0,0,0,6,7,8,9,10,11,12,13,14,15,16,17,18,19,0,0,0,0,0,0,0,0,0,0,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,0,0,0,0,0,0,0,0,0,0,0,0,0],
    [0,0,0,0,0,5,6,7,8,9,10,11,12,13,14,15,16,17,18,0,0,0,0,0,0,0,0,0,0,0,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,0,0,0,0,0,0,0,0,0,0,0,0],
    [0,0,0,0,0,5,6,7,8,9,10,11,12,13,14,15,16,0,0,0,0,0,0,0,0,0,0,0,0,29,30,0,0,0,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,0,0,0,0,0,0,0,0,0,0,0,0],
    [0,0,0,0,0,5,6,7,8,9,10,11,12,13,14,0,0,0,0,0,0,0,0,0,0,0,0,0,0,29,0,0,0,33,34,35,0,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,0,0,0,0,0,0,0,0,0,0,0,0],
    [0,0,0,0,0,5,6,7,8,9,10,11,12,13,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,29,30,31,32,0,0,0,0,0,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,0,0,0,0,0,0,0,0,0,0,0,0],
    [0,0,0,0,0,5,6,7,8,9,10,11,12,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0],
    [0,0,0,0,0,0,6,7,8,9,0,0,0,13,0,0,0,0,0,0,0,0,0,0,0,0,0,27,28,29,30,31,32,33,34,35,36,37,0,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0],
    [0,0,0,0,0,0,6,7,8,0,0,0,12,13,14,0,0,0,0,0,0,0,0,0,0,0,0,27,28,29,30,31,32,33,34,35,36,37,0,39,40,41,42,0,0,0,46,47,48,49,50,51,52,53,54,55,56,57,0,0,0,0,0,0,0,0,0,0,0,0,0,0],
    [0,0,0,0,0,0,0,7,8,0,10,11,0,13,14,15,16,0,0,0,0,0,0,0,0,0,0,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,0,0,46,47,48,49,0,51,52,53,54,0,0,57,0,0,0,0,0,0,0,0,0,0,0,0,0,0],
    [0,0,0,0,0,0,0,0,8,9,10,11,0,0,0,0,0,17,0,0,0,0,0,0,0,25,0,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,0,0,0,0,0,47,48,0,0,51,52,53,54,0,0,57,0,0,0,0,0,0,0,0,0,0,0,0,0,0],
    [0,0,0,0,0,0,0,0,0,0,0,11,0,0,14,0,0,17,0,0,0,0,0,0,0,0,0,27,28,29,30,31,32,33,34,35,36,37,38,39,40,0,0,0,0,0,0,47,0,0,0,0,52,53,54,0,0,57,58,0,0,0,0,0,0,0,0,0,0,0,0,0],
    [0,0,0,0,0,0,0,0,0,0,0,0,12,13,14,15,16,17,0,0,0,0,0,0,0,0,0,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,0,0,0,0,0,0,48,0,0,0,52,0,0,0,0,57,58,0,0,0,0,0,0,0,0,0,0,0,0,0],
    [0,0,0,0,0,0,0,0,0,0,0,0,0,13,14,15,16,17,18,0,0,0,0,0,0,0,0,0,28,29,30,31,32,33,34,35,36,37,38,39,40,41,0,0,0,0,46,0,0,0,0,0,52,53,0,0,56,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0],
    [0,0,0,0,0,0,0,0,0,0,0,0,12,13,14,15,16,17,18,0,0,0,0,0,0,0,0,0,0,0,0,0,32,33,34,35,36,37,38,39,40,0,0,0,0,0,0,0,0,0,0,0,0,53,0,55,56,57,58,59,0,0,0,0,0,0,0,0,0,0,0,0],
    [0,0,0,0,0,0,0,0,0,0,0,0,12,13,14,15,16,17,18,19,20,0,0,0,0,0,0,0,0,0,0,0,0,33,34,35,36,37,38,39,0,0,0,0,0,0,0,0,0,0,0,0,0,53,54,55,56,57,0,59,60,61,62,0,64,0,0,0,0,0,0,0],
    [0,0,0,0,0,0,0,0,0,0,0,0,12,13,14,15,16,17,18,19,20,21,22,0,0,0,0,0,0,0,0,0,0,33,34,35,36,37,38,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,54,55,0,0,0,0,0,61,62,63,64,65,0,0,0,0,0,0],
    [0,0,0,0,0,0,0,0,0,0,0,0,0,13,14,15,16,17,18,19,20,21,22,0,0,0,0,0,0,0,0,0,0,33,34,35,36,37,38,39,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,57,58,0,0,0,0,63,64,0,66,0,0,0,0,0],
    [0,0,0,0,0,0,0,0,0,0,0,0,0,13,14,15,16,17,18,19,20,21,0,0,0,0,0,0,0,0,0,0,0,33,34,35,36,37,38,39,0,41,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,59,60,0,62,0,0,0,0,0,0,0,0,0],
    [0,0,0,0,0,0,0,0,0,0,0,0,0,0,14,15,16,17,18,19,20,21,0,0,0,0,0,0,0,0,0,0,0,33,34,35,36,37,38,0,40,41,0,0,0,0,0,0,0,0,0,0,0,0,0,55,56,57,58,59,60,61,62,0,0,0,0,67,0,69,0,71],
    [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,15,16,17,18,19,20,21,0,0,0,0,0,0,0,0,0,0,0,33,34,35,36,37,38,0,40,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,56,57,58,59,60,61,62,63,0,0,66,0,0,0,0,71],
    [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,15,16,17,18,19,20,0,0,0,0,0,0,0,0,0,0,0,0,33,34,35,36,37,0,0,40,0,0,0,0,0,0,0,0,0,0,0,0,0,0,55,56,57,58,59,60,61,62,63,0,0,0,0,0,0,0,0],
    [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,15,16,17,18,19,0,0,0,0,0,0,0,0,0,0,0,0,0,0,34,35,36,37,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,55,56,57,58,59,60,61,62,63,0,0,0,0,0,0,0,0],
    [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,15,16,17,18,19,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,35,36,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,55,56,57,58,59,60,61,62,63,0,0,0,0,0,0,0,0],
    [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,15,16,17,18,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,60,61,62,0,0,0,0,67,0,0,0,0],
    [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,15,16,17,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,60,61,0,0,0,0,66,67,0,0,0,0],
    [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,16,17,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,60,0,0,0,0,65,66,0,0,0,0,0],
    [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,16,17,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,64,0,0,0,0,0,0,0],
    [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,16,17,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0],
    [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,17,18,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
  ];
  var squareSize = 12;
  var nonZeroIndices = [];
  var rows = map.length, cols=map[0].length;
  for (var row=0; row<rows; ++row){
    for (var col=0; col<cols; ++col){
      if (map[row][col]) nonZeroIndices.push( [col*squareSize,row*squareSize] );
    }
  }
  var nonZeroes = nonZeroIndices.length;

  window.onload = function(){
    var layer1 = document.getElementById("backdrop");
    var ctx1   = layer1.getContext('2d');
    var red=255, offset=5;
    var w = layer1.width  = map[0].length * squareSize;
    var h = layer1.height = map.length    * squareSize;
    ctx1.strokeStyle = '#000';
    var drawMap = function(){
      ctx1.clearRect(0,0,w,h);
      red -= offset;
      ctx1.fillStyle = 'rgb('+red+',0,0)';
      for (var i=0; i<nonZeroes; ++i){
        var xy = nonZeroIndices[i];
        ctx1.fillRect(xy[0],xy[1],squareSize,squareSize);
        ctx1.strokeRect(xy[0],xy[1],squareSize,squareSize);
      }
      if (red<0 || red>255) offset *= -1;
    };
    setInterval( drawMap, 1000/30 );
  };
 
<div id="canvasesdiv" style="position:relative; width:864px; height:456px">
  <canvas id="world-map" width="864" height="456" style="position:absolute; left:0px; top:0px; z-index:1;"></canvas>
  <canvas id="backdrop" width="864" height="456" style="position:absolute; left:0px; top:0px; z-index:0;"></canvas>
</div>
 
 
 

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HTML5 Canvas动画使用88-98％的CPU [英] HTML5 Canvas animation uses 88-98% of CPU

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HTML5 Canvas动画使用88-98％的CPU [英] HTML5 Canvas animation uses 88-98% of CPU

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