Black and white pictures created from C# turn black in Windows photos app (code used to work)

[evert823]

I'm having the same problem that is described here:

Pictures turning black in Photos app of Windows 11/10

If pictures are turning black after opening in the Windows Photos app, it could be because of app file corruption. Do this to fix the issue.

www.thewindowsclub.com

But I experience it specifically with black and white images created by my own C# project.
For reference I've posted the code below - it worked fine some years ago but no longer today.

Because I trust my Windows version 11 pro to be up to date and fine, I have this question:
Can I do anything from the C# code in order to fix this?

        public void SaveMazeAsImage(string pFileName)
        {
            int w = (MyMaze.MazeWidth * PixelsPerCell) + (edgemarge * 2);
            int h = (MyMaze.MazeHeight * PixelsPerCell) + (edgemarge * 2);

            Bitmap MyBitmap;
            Graphics g;

            MyBitmap = new Bitmap(w, h);
            g = Graphics.FromImage(MyBitmap);

            Pen blackPen = new Pen(Color.Black, PenWidth);

            g.DrawLine(blackPen, edgemarge, edgemarge, edgemarge, h - edgemarge);
            g.DrawLine(blackPen, edgemarge, h- edgemarge, w - edgemarge, h - edgemarge);
            g.DrawLine(blackPen, w - edgemarge, edgemarge, w - edgemarge, h - edgemarge);
            g.DrawLine(blackPen, w - edgemarge, edgemarge, edgemarge, edgemarge);

            int i;
            int j;
            
            for (i = 0; i < this.MyMaze.MazeWidth; i++)
            {
                for (j = 0; j < this.MyMaze.MazeHeight; j++)
                {
                    Surrounding MySurrounding = this.CellSurrounding(i, j);

                    if (MyMaze.CellSetColor[i, j] != MarkColor.White)
                    {
                        Rectangle rect = new Rectangle(MySurrounding.leftx + (2 * edgemarge), MySurrounding.topy + (2 * edgemarge), PixelsPerCell - (4 * edgemarge), PixelsPerCell - (4 * edgemarge));

                        SolidBrush somecolorBrush = new SolidBrush(Color.White);

                        switch (MyMaze.CellSetColor[i, j])
                        {
                            case MarkColor.Blue:
                                somecolorBrush.Color = Color.Blue;
                                break;
                            case MarkColor.Red:
                                somecolorBrush.Color = Color.Red;
                                break;
                            case MarkColor.Green:
                                somecolorBrush.Color = Color.Green;
                                break;
                            case MarkColor.Yellow:
                                somecolorBrush.Color = Color.Yellow;
                                break;
                        }


                        g.FillRectangle(somecolorBrush, rect);
                    }
                    if (i < this.MyMaze.MazeWidth - 1)
                    {
                        if (this.MyMaze.MyWallsOfCell[i, j].OpenToRight == false)
                        {
                            g.DrawLine(blackPen, MySurrounding.rightx, MySurrounding.bottomy, MySurrounding.rightx, MySurrounding.topy);
                        }
                    }
                    if (j < this.MyMaze.MazeHeight - 1)
                    {
                        if (this.MyMaze.MyWallsOfCell[i, j].OpenToTop == false)
                        {
                            g.DrawLine(blackPen, MySurrounding.leftx, MySurrounding.topy, MySurrounding.rightx, MySurrounding.topy);
                        }
                    }
                }
            }

            MyBitmap.Save(pFileName, ImageFormat.Png);
            MyBitmap.Save(pFileName + ".jpg", ImageFormat.Jpeg);
            MyBitmap.Save(pFileName + ".bmp", ImageFormat.Bmp);
        }

 

[evert823]

Solved,

A default background color must be explicitly assigned, relying on white being a default color won't work:

            MyBitmap = new Bitmap(w, h);
            g = Graphics.FromImage(MyBitmap);

            Rectangle fullrect = new Rectangle(0, 0, w, h);
            SolidBrush backgroundColorBrush = new SolidBrush(Color.White);
            g.FillRectangle(backgroundColorBrush, fullrect);