image file thumb

gistfile1.txt

    class Program
    {
        public static void GenerateImageFileThumb(string file, string outputFile, float width, float height, ThumbOption option)
        {
            if (option == ThumbOption.Scale)
            {
                using (Bitmap image = new Bitmap(file))
                {
                    float scale = Math.Min(width / image.Width, height / image.Height);
                    var scaleWidth = (int)(image.Width * scale);
                    var scaleHeight = (int)(image.Height * scale);

                    var bmp = new Bitmap(scaleWidth, scaleHeight);
                    var graph = Graphics.FromImage(bmp);

                    var brush = new SolidBrush(Color.Transparent);
                    graph.FillRectangle(brush, new RectangleF(0, 0, scaleWidth, scaleHeight));
                    graph.DrawImage(image, new Rectangle(0, 0, scaleWidth, scaleHeight), 0, 0, image.Width, image.Height, GraphicsUnit.Pixel);
                    bmp.Save(outputFile);
                }
            }
            else if (option == ThumbOption.FillTransparency)
            {
                using (Bitmap image = new Bitmap(file))
                {
                    float scale = Math.Min(width / image.Width, height / image.Height);
                    var scaleWidth = (int)(image.Width * scale);
                    var scaleHeight = (int)(image.Height * scale);

                    var bmp = new Bitmap((int)width, (int)height);
                    var graph = Graphics.FromImage(bmp);

                    var brush = new SolidBrush(Color.Transparent);
                    graph.FillRectangle(brush, new RectangleF(0, 0, width, height));
                    var startX = (int)(Math.Abs(width - scaleWidth) / 2);
                    var startY = (int)(Math.Abs(height - scaleHeight) / 2);
                    graph.DrawImage(image, new Rectangle(startX, startY, scaleWidth, scaleHeight), 0, 0, image.Width, image.Height, GraphicsUnit.Pixel);
                    bmp.Save(outputFile);
                }
            }
            else
            {
                using (Bitmap image = new Bitmap(file))
                {
                    float scale = Math.Min(image.Width / width, image.Height / height);
                    var scaleWidth = (int)(image.Width / scale);
                    var scaleHeight = (int)(image.Height / scale);

                    var bmp = new Bitmap((int)width, (int)height);
                    var graph = Graphics.FromImage(bmp);

                    var brush = new SolidBrush(Color.Transparent);
                    graph.FillRectangle(brush, new RectangleF(0, 0, width, height));
                    var startX = (int)((width - scaleWidth) / 2);
                    var startY = (int)((height - scaleHeight) / 2);
                    graph.DrawImage(image, new Rectangle(startX, startY, scaleWidth, scaleHeight), 0, 0, image.Width, image.Height, GraphicsUnit.Pixel);
                    bmp.Save(outputFile);
                }
            }
        }
   }
   
    public enum ThumbOption
    {
        Scale,
        FillTransparency,
        Cover
    }