private void pbBackground_Click(object sender, EventArgs e)
        {
            PickImagePopup frm = new PickImagePopup(ImageTarget.Background, FillType.Image, Ap.BoardTheme.BoardBackgroundImage);

            if (frm.ShowDialog() == DialogResult.OK)
            {
                switch (frm.FillType)
                {
                case FillType.Color:
                    Ap.BoardTheme.BoardBackgroundColor   = frm.SelectedColor;
                    Ap.BoardTheme.IsBoardBackgroundImage = false;
                    LoadColors();
                    break;

                case FillType.Image:
                    Ap.BoardTheme.BoardBackgroundImage   = frm.SelectedImage;
                    Ap.BoardTheme.IsBoardBackgroundImage = true;
                    LoadColors();
                    break;

                default:
                    break;
                }
            }
        }
        private void pbDarkSquares_Click(object sender, EventArgs e)
        {
            PickImagePopup frm = new PickImagePopup(ImageTarget.DarkSquare, FillType.Image, Ap.BoardTheme.DarkSquaresImage);

            if (frm.ShowDialog() == DialogResult.OK)
            {
                SetCustomTheme();
                switch (frm.FillType)
                {
                case FillType.Color:
                    Ap.BoardTheme.DarkSquaresColor = frm.SelectedColor;
                    Ap.BoardTheme.IsSquareImage    = false;
                    LoadColors();
                    break;

                case FillType.Image:
                    Ap.BoardTheme.DarkSquaresImage = frm.SelectedImage;
                    Ap.BoardTheme.IsSquareImage    = true;
                    LoadColors();
                    break;

                default:
                    break;
                }
            }
        }