Source -> http://stackoverflow.com/questions/10322341/simple-algorithm-for-drawing-filled-ellipse-in-c-c

/// <summary>
        /// Draws a filled Ellipse.
        /// </summary>
        /// <param name="image">
        /// The destination image.
        /// </param>
        /// <param name="x">
        /// The x left most position of the ellipse.
        /// </param>
        /// <param name="y">
        /// The y top most position of the ellipse.
        /// </param>
        /// <param name="width">
        /// The width of the ellipse.
        /// </param>
        /// <param name="height">
        /// The height of the ellipse.
        /// </param>
        /// <param name="color">
        /// The color to use.
        /// </param>
        public static void FillEllipse<T>(this GenericImage<T> image, int x, int y, int width, int height, T color)
        {
            width = width / 2;
            height = height / 2;
            var centerX = x + width;
            var centerY = y + height;

            // source -> http://stackoverflow.com/questions/10322341/simple-algorithm-for-drawing-filled-ellipse-in-c-c
            for (var indexY = -height; indexY <= height; indexY++)
            {
                for (var indexX = -width; indexX <= width; indexX++)
                {
                    var dx = indexX / (double)width;
                    var dy = indexY / (double)height;
                    if (dx * dx + dy * dy <= 1)
                    {
                        image[centerX + indexX, centerY + indexY] = color;
                    }
                }
            }
        }