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var map:BitmapData = new BitmapData(w, h, false, 0xFF808080);
map.lock();
var center:Point = new Point(w / 2, h / 2);
var rmax:Number = Math.sqrt(Math.pow(center.x, 2) + Math.pow(center.y, 2));

for (var x:int = 0; x < w; x++) {
	for (var y:int = 0; y < h; y++) {
		var xpos:Number = center.x - x;
		var ypos:Number = center.y - (h-y);
		var radius:Number = Math.sqrt(xpos * xpos + ypos * ypos);

		var theta:Number = 0;
		if (xpos != 0) {
			theta = Math.atan(ypos / xpos);
			if (xpos < 0) theta = theta + Math.PI;
		} else if (ypos != 0) {
			theta = 2 * Math.atan(1) - Math.atan(xpos / ypos);
		}

		var r:Number = 0x7f * (theta / (Math.PI * 2)) + 0x80;
		var g:Number = 0x80;
		// TODO 色の変換が間違ってるっぽい
		var b:Number = 0xFF * (radius / rmax);
		var color:Number = r << 16 | g << 8 | b;

		map.setPixel(x, y, color);
	}
}
map.unlock();