这段就写在主帧上:
function clickHandler(e:MouseEvent):void
{
    var bitmapdata:BitmapData = new BitmapData(video.width, video.height);
    bitmapdata.draw(video);
    var jpgEncoder:JPGEncoder = new JPGEncoder(100);//图片质量
    var jpgStream:ByteArray = jpgEncoder.encode(bitmapdata);
    var header:URLRequestHeader = new URLRequestHeader ("Content-type", "application/octet-stream");
    var jpgURLRequest:URLRequest = new URLRequest ("http://192.168.0.87/php.php?name=camera.jpg");
    jpgURLRequest.requestHeaders.push(header);
    jpgURLRequest.method = URLRequestMethod.POST;
    jpgURLRequest.data = jpgStream;
    navigateToURL(jpgURLRequest, "_blank");
}
var video:Video = new Video;
addChild(video);
video.attachCamera(Camera.getCamera());
var btn:Sprite = new Sprite;
btn.graphics.beginFill(0,1);
btn.graphics.drawRoundRect(0,0,100,25,10);
btn.x = 110;
btn.y = 250;
btn.buttonMode = true;
btn.addEventListener(MouseEvent.CLICK, clickHandler);
addChild(btn);

要用到的库文件:

php文件：
if ( isset ( $GLOBALS["HTTP_RAW_POST_DATA"] )) {
    $im = $GLOBALS["HTTP_RAW_POST_DATA"];
    header('Content-Type: image/jpeg');
    header("Content-Disposition: attachment; filename=".$_GET['name']);
    echo $im;
}  else echo '不可预料的错误！';
?>