把圆形像素换成矩形像素

//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);