//圆形像素
//cxt.arc(x+j*2*(RADIUS+1)+(RADIUS+1),y+i*2*(RADIUS+1)+(RADIUS+1),RADIUS,0,2*Math.PI);
//矩形像素
cxt.moveTo(x+j*2*(RADIUS+1)+1,y+i*2*(RADIUS+1)+1);
cxt.lineTo(x+j*2*(RADIUS+1)+1+2*RADIUS,y+i*2*(RADIUS+1)+1);
cxt.lineTo(x+j*2*(RADIUS+1)+1+2*RADIUS,y+i*2*(RADIUS+1)+1+2*RADIUS);
cxt.lineTo(x+j*2*(RADIUS+1)+1,y+i*2*(RADIUS+1)+1+2*RADIUS);