Gridtools maxrect with a fixed bug

using ConsoleLib.Console;
using System.Collections.Generic;

namespace Genkit
{
    public static class GridTools
    {
        public static void DrawIntGrid( int[,] Grid, Rect2D R, bool bWait = true )
        {
            // TODO:change this to not draw a dependency on Qud's display library
            ScreenBuffer SB = XRL.UI.Popup.ScrapBuffer;

            for (int x = 0; x <= Grid.GetUpperBound(0); x++)
                for (int y = 0; y <= Grid.GetUpperBound(1); y++)
                {
                    SB.Goto(x, y);
                    if( x >= R.x1 && x <= R.x2 && y >= R.y1 && y <= R.y2 )
                    {
                        SB.Write("#");
                    }
                    else
                    {
                        string hexValue = Grid[x, y].ToString("X");
                        SB.Write(hexValue);
                    }
                }

            XRL.Core.XRLCore._Console.DrawBuffer(SB);
            if( bWait ) Keyboard.getch();
        }

        public static void DrawIntGrid(int[,] Grid,bool bWait = true)
        {
            // TODO:change this to not draw a dependency on Qud's display library
            ScreenBuffer SB = XRL.UI.Popup.ScrapBuffer;
            SB.Clear();


            for (int x = 0; x <= Grid.GetUpperBound(0); x++)
                for (int y = 0; y <= Grid.GetUpperBound(1); y++)
                {
                    SB.Goto(x, y);
                    int g = Grid[x, y];
                    string hexValue = Grid[x, y].ToString("X");

                    if (g > 15)
                    {
                        g -= 16;
                        hexValue = "&G" + Grid[x, y].ToString("X");
                    }

                    if (g > 15)
                    {
                        g -= 16;
                        hexValue = "&W"+Grid[x, y].ToString("X");
                    }

                    if (g > 15)
                    {
                        g -= 16;
                        hexValue = "&R" + Grid[x, y].ToString("X");
                    }


                    SB.Write(hexValue);
                }

            XRL.Core.XRLCore._Console.DrawBuffer(SB);
            if (bWait) Keyboard.getch();
        }

        public static Rect2D MaxRectSize(int[,] Grid)
        {
            Rect2D MaxRect = Rect2D.zero;

            DrawIntGrid(Grid);
            int[,] Histogram = new int[Grid.GetUpperBound(0)+1,Grid.GetUpperBound(1)+1];

            // Generate sub-histograms per row
            for( int x=0;x<=Grid.GetUpperBound(0);x++)
            {
                int nCount = 0;
                for ( int y=0;y<=Grid.GetUpperBound(1);y++ )
                {
                    if( Grid[x,y] == 0 )
                    {
                        nCount++;
                    }
                    else
                    {
                        nCount = 0;
                    }

                    Histogram[x, y] = nCount;
                }
            }
            DrawIntGrid(Histogram);

            // Solve each histogram's rects using stack method http://stackoverflow.com/questions/4311694/maximize-the-rectangular-area-under-histogram
            Stack<int> ColumnStack = new Stack<int>();
            int[,] Area = new int[Grid.GetUpperBound(0) + 1, Grid.GetUpperBound(1) + 1];
            int[,] Left = new int[Grid.GetUpperBound(0) + 1, Grid.GetUpperBound(1) + 1];
            int[,] Right = new int[Grid.GetUpperBound(0) + 1, Grid.GetUpperBound(1) + 1];

            for (int y = 0; y <= Grid.GetUpperBound(1); y++)
            {
                int i, t;
                ColumnStack.Clear();

                for( i = 0;i<=Grid.GetUpperBound(0);i++)
                {
                    while( ColumnStack.Count > 0 )
                    {
                        if(Histogram[i,y] <= Histogram[ColumnStack.Peek(),y] )
                        {
                            ColumnStack.Pop();
                        }
                        else
                        {
                            break;
                        }
                    }

                    if( ColumnStack.Count == 0 )
                    {
                        t = -1;
                    }
                    else
                    {
                        t = ColumnStack.Peek();
                    }

                    Area[i,y] = i - t - 1;
                    Left[i, y] = i - t - 1;
                    ColumnStack.Push(i);
                }

                ColumnStack.Clear();

                for( i = Grid.GetUpperBound(0);i>=0;i--)
                {
                    while (ColumnStack.Count > 0)
                    {
                        if (Histogram[i, y] <= Histogram[ColumnStack.Peek(), y])
                        {
                            ColumnStack.Pop();
                        }
                        else
                        {
                            break;
                        }
                    }

                    if (ColumnStack.Count == 0)
                    {
                        t = Grid.GetUpperBound(0)+1;
                    }
                    else
                    {
                        t = ColumnStack.Peek();
                    }

                    Area[i,y] += t - i - 1;
                    Right[i, y] = t - i - 1;
                    ColumnStack.Push(i);
                }
            }
            DrawIntGrid(Area);

            int MaxArea = 0;

            //Calculating Area[i] and find max Area
            for (int y = 0; y <= Grid.GetUpperBound(1); y++)
            for (int i = 0; i <= Grid.GetUpperBound(0); i++)
            {
                int Width = Area[i, y] + 1;
                Area[i, y] = Histogram[i, y] * (Area[i, y] + 1);
                if( Area[i,y] > MaxArea )
                {
                    MaxRect.x1 = i - Left[i,y];
                    MaxRect.x2 = i + Right[i, y];

                    MaxRect.y2 = y;
                    MaxRect.y1 = y - (Histogram[i, y]) + 1;

                    MaxArea = Area[i, y];
                }
            }

            DrawIntGrid(Area);
            DrawIntGrid(Area,MaxRect);
            return MaxRect;
        }
    }
}