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HTML5 Canvas 在 FireFox 4 中闪烁

发布于 2024-11-01 18:17:58 字数 2448 浏览 3 评论 0原文

我正在 HTML5 画布上进行概念验证。我能够在 Chrome 和 IE9 中像魅力一样工作，但在 Firefox 4 中，当它重新绘制画布时，我会不断闪烁。我已经尝试了该网站上提到的一些技术，例如双缓冲，但仍然出现大量闪烁。任何对此的见解将不胜感激！

<!DOCTYPE HTML>
<html>
<head>
<style type="text/css">  
body
{  
    margin:0px;  
    padding:0px;  
    text-align:center;  
} 
canvas
{  
    outline:0;  
    border:1px solid #000;  
    margin-top: 10px;
    margin-left: auto;  
    margin-right: auto;  
}  
</style>
<script type="text/javascript">
var canvasWidth = 640;
var thisXPos = 0;
var canvasHeight = 820;
var thisYPos = 0;
var canvas = null;
var context = null;
var gLoop = null;
var rain = [];
var rainImg = "images/raindrop.gif";
var bgImg = null;
var i;

for (i = 0; i < howManyLetters; i++)
{
    rain.push([Math.floor(Math.random() * canvasWidth), Math.floor(Math.random() * canvasHeight),rainImg]);
}

var DrawRain = function()
{
    for (i = 0; i < 10; i++)
    {
        thisXPos = rain[i][0];
        thisYPos = rain[i][1];
        imgSrc = rain[i][2];
        letterImg = new Image();
        letterImg.setAtX = thisXPos;
        letterImg.setAtY = thisYPos;
        letterImg.onload = function()
        {
            context.drawImage(this, this.setAtX, this.setAtY);
        }
        letterImg.src = imgSrc;
    }
};

var MoveRain = function(e)
{
    for (i = 0; i < 10; i++)
    {
        if ((rain[i][1] - 5) > canvasHeight)
        {
            randomnumber = Math.floor(Math.random()*26);

            rain[i][0] = Math.random() * canvasWidth;
            rain[i][1] = 0;
            rain[i][2] = rainImg;
        }
        else
        {
            rain[i][1] += e;
        }
    }
};

var clear = function()
{
    context.beginPath();
    context.rect(0, 0, canvasWidth, canvasHeight);
    context.closePath();

    bgImg = new Image();
    bgImg.src = "images/bg.png";
    bgImg.onload = function()
    {
        context.drawImage(bgImg,0,0);
    }
} 

var GameLoop = function()
{
    context.save();
    clear();
    MoveRain(1);
    DrawRain();
    context.restore();

    gLoop = setTimeout(GameLoop, 10);
}

function loadGame()
{
    canvas = document.getElementById("gameCanvas");
    context = canvas.getContext("2d");
    canvas.width = canvasWidth;
    canvas.height = canvasHeight;

    GameLoop();
}

</script>
</head>
<body onload="loadGame();">
    <canvas id="gameCanvas"></canvas>
</body>
</html>
原文

I'm working on a proof of concept on an HTML5 canvas. I was able to get this working like a charm in Chrome and IE9, but in Firefox 4 I'm getting constant flicker as it redraws the canvas. I've tried a few techniques mentioned on this site like double buffering but I'm still getting a large amount of flicker. Any insight on this would be appreciated!

<!DOCTYPE HTML>
<html>
<head>
<style type="text/css">  
body
{  
    margin:0px;  
    padding:0px;  
    text-align:center;  
} 
canvas
{  
    outline:0;  
    border:1px solid #000;  
    margin-top: 10px;
    margin-left: auto;  
    margin-right: auto;  
}  
</style>
<script type="text/javascript">
var canvasWidth = 640;
var thisXPos = 0;
var canvasHeight = 820;
var thisYPos = 0;
var canvas = null;
var context = null;
var gLoop = null;
var rain = [];
var rainImg = "images/raindrop.gif";
var bgImg = null;
var i;

for (i = 0; i < howManyLetters; i++)
{
    rain.push([Math.floor(Math.random() * canvasWidth), Math.floor(Math.random() * canvasHeight),rainImg]);
}

var DrawRain = function()
{
    for (i = 0; i < 10; i++)
    {
        thisXPos = rain[i][0];
        thisYPos = rain[i][1];
        imgSrc = rain[i][2];
        letterImg = new Image();
        letterImg.setAtX = thisXPos;
        letterImg.setAtY = thisYPos;
        letterImg.onload = function()
        {
            context.drawImage(this, this.setAtX, this.setAtY);
        }
        letterImg.src = imgSrc;
    }
};

var MoveRain = function(e)
{
    for (i = 0; i < 10; i++)
    {
        if ((rain[i][1] - 5) > canvasHeight)
        {
            randomnumber = Math.floor(Math.random()*26);

            rain[i][0] = Math.random() * canvasWidth;
            rain[i][1] = 0;
            rain[i][2] = rainImg;
        }
        else
        {
            rain[i][1] += e;
        }
    }
};

var clear = function()
{
    context.beginPath();
    context.rect(0, 0, canvasWidth, canvasHeight);
    context.closePath();

    bgImg = new Image();
    bgImg.src = "images/bg.png";
    bgImg.onload = function()
    {
        context.drawImage(bgImg,0,0);
    }
} 

var GameLoop = function()
{
    context.save();
    clear();
    MoveRain(1);
    DrawRain();
    context.restore();

    gLoop = setTimeout(GameLoop, 10);
}

function loadGame()
{
    canvas = document.getElementById("gameCanvas");
    context = canvas.getContext("2d");
    canvas.width = canvasWidth;
    canvas.height = canvasHeight;

    GameLoop();
}

</script>
</head>
<body onload="loadGame();">
    <canvas id="gameCanvas"></canvas>
</body>
</html>

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评论（2）

夏了南城 2024-11-08 18:17:58

我将您的示例提炼为：

http://jsfiddle.net/sPm3b/6/

并且它在 Firefox 和 Chrome 中运行得非常快。

所以我们知道问题出在图像上。

您需要优化它们的创建和加载方式。现在，每个 clear() 都会创建一个新图像并等待它加载！该图像只能在您的 loadGame() 中创建一次，然后一遍又一遍地重复使用。

与 DrawRain() 中的 letterImg 的处理完全相同。将其创建移至 loadGame()

这可能会解决问题。

编辑：

像这样：

在顶部添加：

var letterImg = new Image();
var bgImg = new Image();

然后

function loadGame()
{
    canvas = document.getElementById("gameCanvas");
    context = canvas.getContext("2d");
    canvas.width = canvasWidth;
    canvas.height = canvasHeight;

    bgImg.src = "images/bg.png";
    letterImg.src = "images/raindrop.gif";

    // optional: wait for them to load here

    GameLoop();
}

然后drawRain，例如，看起来像这样：

var DrawRain = function()
{
    for (i = 0; i < 10; i++)
    {
        thisXPos = rain[i][0];
        thisYPos = rain[i][1];
        context.drawImage(letterImg, thisXPosX, thisYPos); // letterImg was already constructed, no need to make it again
    }
};

I have distilled your example down to this:

http://jsfiddle.net/sPm3b/6/

And it works very fast in Firefox and Chrome.

So we know that the problem lies in the images.

You need to optimize how they are created and loaded. Right now, each clear() creates a new image and waits for it to load! That image should be created only once, in your loadGame() and then reused over and over.

Same exact deal with letterImg in DrawRain(). Move the creation of it to loadGame()

That will probably fix the problem.

EDIT:

like this:

At the top add:

var letterImg = new Image();
var bgImg = new Image();

Then

function loadGame()
{
    canvas = document.getElementById("gameCanvas");
    context = canvas.getContext("2d");
    canvas.width = canvasWidth;
    canvas.height = canvasHeight;

    bgImg.src = "images/bg.png";
    letterImg.src = "images/raindrop.gif";

    // optional: wait for them to load here

    GameLoop();
}

Then drawRain, for example, would look like this:

var DrawRain = function()
{
    for (i = 0; i < 10; i++)
    {
        thisXPos = rain[i][0];
        thisYPos = rain[i][1];
        context.drawImage(letterImg, thisXPosX, thisYPos); // letterImg was already constructed, no need to make it again
    }
};
回复 原文
屌丝范 2024-11-08 18:17:58

作为对西蒙·萨里斯回应的补充。我使用了“双画布”技术来避免屏幕因厚画布而闪烁。

它的工作方式是始终有 2 个版本的画布，一种在 DOM 中，一种在外部，并且总是在不在 DOM 中的画布上绘制。我将它与重绘队列一起使用。

这是工作代码的一部分

(...)
clear: function() {
    //rotating on 2 canvas, one for draw (outside DOM) one for show
    var self = this;
    if (null == self.canvasbackup) {
        var tmpcanvas = self.canvas.clone(true);
        self.canvasbackup = self.canvas;
        self.canvas=tmpcanvas;
    } else {
        var tmpcanvas = self.canvasbackup;
        self.canvasbackup = self.canvas;
        self.canvas=tmpcanvas;
    }
    self.ctx = self.canvas[0].getContext('2d');
    self.ctx.clearRect( 0, 0, self.options.width, self.options.height );
    jQuery.each(self.elements,function(idx,elt){
        // custom function: my elements need to know which canvas they depends on
        elt.reconnectCanvas(self.canvas,self.ctx);
    });
},
inDOM: function() {
    var self = this;
    if(null==self.canvasbackup) {
        //1st time need to get all things in DOM
        self.canvas.appendTo(self.div);
        self.div.appendTo(self.container);
    } else {
        // remove current shown canvas
        self.connectHuman();
        self.canvasbackup.remove();
        // loosing some events here...
        self.canvas.appendTo(self.div);
        // div is already in DOM, we are in redraw
    }
},
redraw: function() {
    var self = this;
    self.clear();
    jQuery.each(self.elements,function(idx,elt){
        elt.draw();
        elt.enddraw();
    });
    self.inDOM();
}
(...)

In complement to Simon Sarris response. I've used a 'double canvas' technique to avoid screen fickering with heavy canvas.

The way it works is always have 2 version of the canvas, one in DOM, one outside, and always draw on the one which is not in DOM. I use it with a redraw queue.

here's a part of a working code

(...)
clear: function() {
    //rotating on 2 canvas, one for draw (outside DOM) one for show
    var self = this;
    if (null == self.canvasbackup) {
        var tmpcanvas = self.canvas.clone(true);
        self.canvasbackup = self.canvas;
        self.canvas=tmpcanvas;
    } else {
        var tmpcanvas = self.canvasbackup;
        self.canvasbackup = self.canvas;
        self.canvas=tmpcanvas;
    }
    self.ctx = self.canvas[0].getContext('2d');
    self.ctx.clearRect( 0, 0, self.options.width, self.options.height );
    jQuery.each(self.elements,function(idx,elt){
        // custom function: my elements need to know which canvas they depends on
        elt.reconnectCanvas(self.canvas,self.ctx);
    });
},
inDOM: function() {
    var self = this;
    if(null==self.canvasbackup) {
        //1st time need to get all things in DOM
        self.canvas.appendTo(self.div);
        self.div.appendTo(self.container);
    } else {
        // remove current shown canvas
        self.connectHuman();
        self.canvasbackup.remove();
        // loosing some events here...
        self.canvas.appendTo(self.div);
        // div is already in DOM, we are in redraw
    }
},
redraw: function() {
    var self = this;
    self.clear();
    jQuery.each(self.elements,function(idx,elt){
        elt.draw();
        elt.enddraw();
    });
    self.inDOM();
}
(...)
回复 原文
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