C# GDI画图，自动识别画板空白区域并返回坐标

        /// <summary>
        /// 获取流程设计器空白区域的x,y坐标
        /// 源码来源：CSFramework.Workflow工作流引擎
        /// </summary>
        /// <param name="width">要绘制的图元宽度</param>
        /// <param name="height">要绘制的图元高度</param>
        /// <returns></returns>
        public Point GetEmptyRegion(int width, int height)
        {
            const int FrameMargin = 50;
            const int MarginLeft = 200;
            const int MarginTop = 100;
            const int offset = 3;//偏移量

            Point point = new Point(MarginLeft, MarginTop);//默认返回的坐标位置
            List<IDrawElement> elements = this.AllElements; //获取设计器所有图元

            if (elements.Count == 0) return point;

            RectangleF[] rect1Scans, rect2Scans;
            Region region1, region2;
            bool isIntersect = false;//表示是否相交

            //通过两层循环设计器的宽度和高度，每次偏移3个像素生成检测区域。
            for (int x = MarginLeft; x <= _BitmapBackground.Width - FrameMargin; x += offset)
            {
                for (int y = MarginTop; y <= _BitmapBackground.Height - FrameMargin; y += offset)
                {
                    region1 = new Region(new Rectangle(x, y, width, height));
                    rect1Scans = region1.GetRegionScans(new Matrix());
                    isIntersect = false;

                    //循环现有节点
                    foreach (var obj in elements)
                    {
                        region2 = obj.Region;
                        rect2Scans = region2.GetRegionScans(new Matrix());
                        using (Region rgnIntersect = region1.Clone())
                        {
                            rgnIntersect.Intersect(region2);//求交集
                            //获取交集的切片
                            RectangleF[] rectIntersect = rgnIntersect.GetRegionScans(new Matrix());

                            //>0:表示区域有交集
                            if (rectIntersect.Length > 0)
                            {
                                isIntersect = true;
                                break;
                            }
                        }
                    }

                    //没有交集，返回坐标
                    if (isIntersect == false)
                    {
                        return new Point(x, y);
                    }
                }
            }

            return point;
        }