illStyle = color;
                        ctx.fillText(char, px, py);
                    }
                }
            }

            // 圆角矩形 polyfill
            if (!CanvasRenderingContext2D.prototype.roundRect) {
                CanvasRenderingContext2D.prototype.roundRect = function (x, y, w, h, r) {
                    this.beginPath();
                    this.moveTo(x + r, y);
                    this.lineTo(x + w - r, y);
                    this.quadraticCurveTo(x + w, y, x + w, y + r);
