C# 將圖檔/Imaget轉換為byte array

以下是2種方式的測試結果，
一是使用FileStream讀入圖檔，
另一是使用System.Drawing.Image讀入圖檔。
           

        // 先將圖檔讀到FileStream, 再轉換為byte array。

        private static void ToBinaryByFileStream(string imageFile)

        {

            FileStream fs = new FileStream(imageFile, FileMode.Open);

            byte[] buffer = new byte[fs.Length];

            fs.Read(buffer, 0, buffer.Length);

            fs.Close();

        }

        // 先將圖檔讀到Image object, 再轉換為byte array。

        private static void ToBinaryByImageObj(string imageFile)

        {

            System.Drawing.Image image = System.Drawing.Image.FromFile(imageFile);

            MemoryStream mr = new MemoryStream();

            image.Save(mr, System.Drawing.Imaging.ImageFormat.Png);

            byte[] binaryImage = mr.ToArray();

            mr.Dispose();

            image.Dispose();

        }

// 測試method。 

public static void ConvertImageToBinary()

        {

            Console.WriteLine("=== Convert the image file to the binary object. ===");

            string imageFolder = @"D:\Images";

            // 測試的image數量。

            int sampleCount = 100;

            string[] imagePaths = Directory.GetFiles(imageFolder, "*.png");

            if (0 == imagePaths.Length)

            {

                Console.WriteLine("No image found.");

                return;

            }

            Stopwatch sw = new Stopwatch();

            sw.Reset();

            sw.Start();

            for (int i = 0; i < sampleCount; i++)

            {

                ToBinaryByFileStream(imagePaths[i]);

            }

            sw.Stop();

            Console.WriteLine("By FileStream: {0} ms.",

                sw.ElapsedMilliseconds);

            sw.Reset();

            sw.Start();

            for (int i = 0; i < sampleCount; i++)

            {

                ToBinaryByImageObj(imagePaths[i]);

            }

            sw.Stop();

            Console.WriteLine("By System.Drawing.Image: {0} ms.",
                sw.ElapsedMilliseconds);

        }

測試100張圖檔的結果

Unit: ms
By FileStream	152
By System.Drawing.Image	2692

Image object會讀取圖檔的相關資訊，
相對地，FileStream只作資料的搬移，所以效能上會快很多。