【C#/WPF】Bitmap、BitmapImage、ImageSource 、byte[]轉換問題

C#/WPF項目中，用到圖像相關的功能時，涉及到多種圖像數據類型的相互轉換問題，這里做了個整理。包含的內容如下：

• Bitmap和BitmapImage相互轉換。
• RenderTargetBitmap –> BitmapImage
• ImageSource –> Bitmap
• BitmapImage和byte[]相互轉換。
• byte[] –> Bitmap

---

StackOverflow上有很多解決方案，這里選擇了試過可行的方法：

• Bitmap和BitmapImage相互轉換
• 谷歌上搜關鍵字 C# WPF Convert Bitmap BitmapImage

// Bitmap --> BitmapImage
public static BitmapImage BitmapToBitmapImage(Bitmap bitmap)
{
    using (MemoryStream stream = new MemoryStream())
    {
        bitmap.Save(stream, ImageFormat.Png); // 坑點：格式選Bmp時，不帶透明度

        stream.Position = 0;
        BitmapImage result = new BitmapImage();
        result.BeginInit();
        // According to MSDN, "The default OnDemand cache option retains access to the stream until the image is needed."
        // Force the bitmap to load right now so we can dispose the stream.
        result.CacheOption = BitmapCacheOption.OnLoad;
        result.StreamSource = stream;
        result.EndInit();
        result.Freeze();
        return result;
    }
}


// BitmapImage --> Bitmap
public static Bitmap BitmapImageToBitmap(BitmapImage bitmapImage)
{
    // BitmapImage bitmapImage = new BitmapImage(new Uri("../Images/test.png", UriKind.Relative));

    using (MemoryStream outStream = new MemoryStream())
    {
        BitmapEncoder enc = new BmpBitmapEncoder();
        enc.Frames.Add(BitmapFrame.Create(bitmapImage));
        enc.Save(outStream);
        Bitmap bitmap = new Bitmap(outStream);

        return new Bitmap(bitmap);
    }
}

• RenderTargetBitmap –> BitmapImage

// RenderTargetBitmap --> BitmapImage
public static BitmapImage ConvertRenderTargetBitmapToBitmapImage(RenderTargetBitmap wbm)
{
    BitmapImage bmp = new BitmapImage();
    using (MemoryStream stream = new MemoryStream())
    {
        BmpBitmapEncoder encoder = new BmpBitmapEncoder();
        encoder.Frames.Add(BitmapFrame.Create(wbm));
        encoder.Save(stream);
        bmp.BeginInit();
        bmp.CacheOption = BitmapCacheOption.OnLoad;
        bmp.CreateOptions = BitmapCreateOptions.PreservePixelFormat;
        bmp.StreamSource = new MemoryStream(stream.ToArray()); //stream;
        bmp.EndInit();
        bmp.Freeze();
    }
    return bmp;
}


// RenderTargetBitmap --> BitmapImage
public static BitmapImage RenderTargetBitmapToBitmapImage(RenderTargetBitmap rtb)
{
    var renderTargetBitmap = rtb;
    var bitmapImage = new BitmapImage();
    var bitmapEncoder = new PngBitmapEncoder();
    bitmapEncoder.Frames.Add(BitmapFrame.Create(renderTargetBitmap));

    using (var stream = new MemoryStream())
    {
        bitmapEncoder.Save(stream);
        stream.Seek(0, SeekOrigin.Begin);

        bitmapImage.BeginInit();
        bitmapImage.CacheOption = BitmapCacheOption.OnLoad;
        bitmapImage.StreamSource = stream;
        bitmapImage.EndInit();
    }

    return bitmapImage;
}

• ImageSource –> Bitmap

// ImageSource --> Bitmap
public static System.Drawing.Bitmap ImageSourceToBitmap(ImageSource imageSource)
{
    BitmapSource m = (BitmapSource)imageSource;

    System.Drawing.Bitmap bmp = new System.Drawing.Bitmap(m.PixelWidth, m.PixelHeight, System.Drawing.Imaging.PixelFormat.Format32bppPArgb); // 坑點：選Format32bppRgb將不帶透明度

    System.Drawing.Imaging.BitmapData data = bmp.LockBits(
    new System.Drawing.Rectangle(System.Drawing.Point.Empty, bmp.Size), System.Drawing.Imaging.ImageLockMode.WriteOnly, System.Drawing.Imaging.PixelFormat.Format32bppPArgb);

    m.CopyPixels(Int32Rect.Empty, data.Scan0, data.Height * data.Stride, data.Stride);
    bmp.UnlockBits(data);

    return bmp;
}

• BitmapImage和byte[]相互轉換

// BitmapImage --> byte[]
public static byte[] BitmapImageToByteArray(BitmapImage bmp)
{
    byte[] bytearray = null;
    try
    {
        Stream smarket = bmp.StreamSource; ;
        if (smarket != null && smarket.Length > 0)
        {
            //設置當前位置
            smarket.Position = 0;
            using (BinaryReader br = new BinaryReader(smarket))
            {
                bytearray = br.ReadBytes((int)smarket.Length);
            }
        }
    }
    catch (Exception ex)
    {
        Console.WriteLine(ex);
    }
    return bytearray;
}


// byte[] --> BitmapImage
public static BitmapImage ByteArrayToBitmapImage(byte[] array)
{
    using (var ms = new System.IO.MemoryStream(array))
    {
        var image = new BitmapImage();
        image.BeginInit();
        image.CacheOption = BitmapCacheOption.OnLoad; // here
        image.StreamSource = ms;
        image.EndInit();
        image.Freeze();
        return image;
    }
}

• byte[] –> Bitmap

public static System.Drawing.Bitmap ConvertByteArrayToBitmap(byte[] bytes)
{
    System.Drawing.Bitmap img = null;
    try
    {
        if (bytes != null && bytes.Length != 0)
        {
            MemoryStream ms = new MemoryStream(bytes);
            img = new System.Drawing.Bitmap(ms);
        }
    }
    catch (Exception ex)
    {
        Console.WriteLine(ex);
    }
    return img;
}