BrightIdeasSoftware.ObjectListView.MakeSortIndicatorImages C# (CSharp) Method

        protected virtual void MakeSortIndicatorImages()
        {
            // Don't mess with the image list in design mode
            if (this.DesignMode)
                return;

            ImageList il = this.SmallImageList;
            if (il == null) {
                il = new ImageList();
                il.ImageSize = new Size(16, 16);
                il.ColorDepth = ColorDepth.Depth32Bit;
            }

            // This arrangement of points works well with (16,16) images, and OK with others
            int midX = il.ImageSize.Width / 2;
            int midY = (il.ImageSize.Height / 2) - 1;
            int deltaX = midX - 2;
            int deltaY = deltaX / 2;

            if (il.Images.IndexOfKey(SORT_INDICATOR_UP_KEY) == -1) {
                Point pt1 = new Point(midX - deltaX, midY + deltaY);
                Point pt2 = new Point(midX, midY - deltaY - 1);
                Point pt3 = new Point(midX + deltaX, midY + deltaY);
                il.Images.Add(SORT_INDICATOR_UP_KEY, this.MakeTriangleBitmap(il.ImageSize, new Point[] { pt1, pt2, pt3 }));
            }

            if (il.Images.IndexOfKey(SORT_INDICATOR_DOWN_KEY) == -1) {
                Point pt1 = new Point(midX - deltaX, midY - deltaY);
                Point pt2 = new Point(midX, midY + deltaY);
                Point pt3 = new Point(midX + deltaX, midY - deltaY);
                il.Images.Add(SORT_INDICATOR_DOWN_KEY, this.MakeTriangleBitmap(il.ImageSize, new Point[] { pt1, pt2, pt3 }));
            }

            this.SmallImageList = il;
        }