function drawChessman(i,j,type){
var img = new Image();
img.onload = function(){
cxt.drawImage(img, w*i-10,w*j-10);
//检查是否已经赢了
checkWin();
};
if(type){//是黑子
img.src="b.png";
}else{
img.src="w.png";
}