我的问题是，使用drawImage方法绘制图像的最佳方式是什么？目标用途是高级的二维粒子效应(游戏开发)，其中粒子随着时间的推移而改变颜色等等。我不是问如何使整个画布变暗，而只是画出我目前的图像。
我已经得出结论，globalAlpha参数会影响当前绘制的图像。
//works with drawImage() canvas2d.globalAlpha = 0.5;
但是，如何使用任意颜色值对每个图像进行着色？如果有某种globalFillStyle或globalColor或某种事情，这将是非常棒的…
编辑：
以下是我正在使用的应用程序的屏幕截图：
http://twitpic.com/1j2aeg/full
alt text http://web20.twitpic.com/img/92485672-1d59e2f85d099210d4dafb5211bf770f.4bd804ef-scaled.png
解决方法
你有合成操作，其中之一是目的地。如果使用’context.globalCompositeOperation =“destination-atop”’将图像合成为纯色，则它将具有前景图像的alpha和背景图像的颜色。我用这个来完成一个完全有色的副本的图像，然后在原始的顶部绘制完全有色的副本，其透明度等于我想要的色彩。
以下是完整的代码：
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<title>HTML5 Canvas Test</title>
<script type="text/javascript">
var x; //drawing context
var width;
var height;
var fg;
var buffer
window.onload = function() {
var drawingCanvas = document.getElementById('myDrawing');
// Check the element is in the DOM and the browser supports canvas
if(drawingCanvas && drawingCanvas.getContext) {
// Initaliase a 2-dimensional drawing context
x = drawingCanvas.getContext('2d');
width = x.canvas.width;
height = x.canvas.height;
// grey Box grid for transparency testing
x.fillStyle = '#666666';
x.fillRect(0,width,height);
x.fillStyle = '#AAAAAA';
var i,j;
for (i=0; i<100; i++){
for (j=0; j<100; j++){
if ((i+j)%2==0){
x.fillRect(20*i,20*j,20,20);
}
}
}
fg = new Image();
fg.src = 'http://uncc.ath.cx/LayerCake/images/16/3.png';
// create offscreen buffer,buffer = document.createElement('canvas');
buffer.width = fg.width;
buffer.height = fg.height;
bx = buffer.getContext('2d');
// fill offscreen buffer with the tint color
bx.fillStyle = '#FF0000'
bx.fillRect(0,buffer.width,buffer.height);
// destination atop makes a result with an alpha channel identical to fg,but with all pixels retaining their original color *as far as I can tell*
bx.globalCompositeOperation = "destination-atop";
bx.drawImage(fg,0);
// to tint the image,draw it first
x.drawImage(fg,0);
//then set the global alpha to the amound that you want to tint it,and draw the buffer directly on top of it.
x.globalAlpha = 0.5;
x.drawImage(buffer,0);
}
}
</script>
</head>
</body>
<canvas id="myDrawing" width="770" height="400">
<p>Your browser doesn't support canvas.</p>
</canvas>
</body>
</html>
