[C#] Image to Base64 後呈現

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2012-10-04

最近有一些圖片控管的需求跟跨 Server 傳遞問題

剛好看到點部落上面有有人發一篇文章 img base64 顯示圖片支援 IE、Firefox、Chorme

想說就順便側一下..

按下按鈕後 Server 會讀取一張根目錄下面 sample.jpg 的圖案之後轉碼為 base64 且設定為 imageSample 的 src 屬性..

將圖片轉 base64

C# Code:

/// <summary>

/// 自動判斷圖片格式

/// </summary>

/// <param name="img"></param>

/// <returns></returns>

public static System.Drawing.Imaging.ImageFormat GetImageFormat(System.Drawing.Image img)

    if (img.RawFormat.Equals(System.Drawing.Imaging.ImageFormat.Jpeg))

        return System.Drawing.Imaging.ImageFormat.Jpeg;

    if (img.RawFormat.Equals(System.Drawing.Imaging.ImageFormat.Bmp))

        return System.Drawing.Imaging.ImageFormat.Bmp;

    if (img.RawFormat.Equals(System.Drawing.Imaging.ImageFormat.Png))

        return System.Drawing.Imaging.ImageFormat.Png;

    if (img.RawFormat.Equals(System.Drawing.Imaging.ImageFormat.Emf))

        return System.Drawing.Imaging.ImageFormat.Emf;

    if (img.RawFormat.Equals(System.Drawing.Imaging.ImageFormat.Exif))

        return System.Drawing.Imaging.ImageFormat.Exif;

    if (img.RawFormat.Equals(System.Drawing.Imaging.ImageFormat.Gif))

        return System.Drawing.Imaging.ImageFormat.Gif;

    if (img.RawFormat.Equals(System.Drawing.Imaging.ImageFormat.Icon))

        return System.Drawing.Imaging.ImageFormat.Icon;

    if (img.RawFormat.Equals(System.Drawing.Imaging.ImageFormat.MemoryBmp))

        return System.Drawing.Imaging.ImageFormat.MemoryBmp;

    if (img.RawFormat.Equals(System.Drawing.Imaging.ImageFormat.Tiff))

        return System.Drawing.Imaging.ImageFormat.Tiff;

    else

        return System.Drawing.Imaging.ImageFormat.Wmf;

/// <summary>

/// 將 Image 物件轉 Base64

/// </summary>

/// <param name="image"></param>

/// <returns></returns>

public string ImageToBase64(System.Drawing.Image image)

    MemoryStream ms = new MemoryStream();

    System.Drawing.Imaging.ImageFormat format = GetImageFormat(image);

    // 將圖片轉成 byte[]

    image.Save(ms, format);

    byte[] imageBytes = ms.ToArray();

    // 將 byte[] 轉 base64

    string base64String = Convert.ToBase64String(imageBytes);

    return base64String;

讓其自動判斷格式

之後我們呼叫這 function

protected void Button1_Click(object sender, EventArgs e)

// 讀取圖片並轉為 Image 物件

var image= System.Drawing.Image.FromFile(AppDomain.CurrentDomain.BaseDirectory + "sample.jpg");

// 設定至 imgSample 並且自動判定格式

imgSample.Src = "data:image/" + GetImageFormat(image) + ";base64," + ImageToBase64(image);

// 將 base64 寫檔案 比較檔案大小

File.WriteAllText(AppDomain.CurrentDomain.BaseDirectory+"base64.txt",imgSample.Src);

看一下檔案大小

圖片從 67KB-> 89 KB 這成長量不容小覷..

Sample: