C＃UWP10中WriteableBitmap中的不正確Byte []

Question

我想從WriteableBitmap獲取base64字符串。 我相信byte []是不正確的。

因為：

從base64創建圖像的代碼正在運行。 從文件發送base64字符串時進行了測試。 但是，當我將我的函數用於WriteableBitmap到base64時，我什么也看不到。

到目前為止我的嘗試。

   public static string GetByteArrayFromImage(WriteableBitmap writeableBitmap)
        {
             Stream stream = writeableBitmap.PixelBuffer.AsStream();
             MemoryStream memoryStream = new MemoryStream();
             stream.CopyTo(memoryStream);
             Byte[] bytes = memoryStream.ToArray();
             return Convert.ToBase64String(bytes);
        }

   public static string GetByteArrayFromImage(WriteableBitmap writeableBitmap)
        {
             Byte[] bytes = writeableBitmap.PixelBuffer.ToArray();
             return Convert.ToBase64String(bytes);
        }

測試例：

   public static async Task<string> GetBase64StringFromFileAsync(StorageFile storageFile)
        {
            Stream ms = await storageFile.OpenStreamForReadAsync();
            byte[] bytes = new byte[(int)ms.Length];
            ms.Read(bytes, 0, (int)ms.Length);
            return Convert.ToBase64String(bytes);
        }

byte []的格式是否錯誤？ 如果是這樣，我該如何糾正？

我的新嘗試

        Stream stream = writeableBitmap.PixelBuffer.AsStream();
        byte[] pixels = new byte[(uint)stream.Length];
        await stream.ReadAsync(pixels, 0, pixels.Length);

        using (var writeStream = new InMemoryRandomAccessStream())
        {
            var encoder = await BitmapEncoder.CreateAsync(BitmapEncoder.PngEncoderId, writeStream);
            encoder.SetPixelData(BitmapPixelFormat.Bgra8, BitmapAlphaMode.Premultiplied, (uint)writeableBitmap.PixelWidth, (uint)writeableBitmap.PixelHeight, 96, 96, pixels);
            await encoder.FlushAsync();
        }
        return Convert.ToBase64String(pixels);

這種嘗試不會將我的byte []更改為正確的fromat。

Answer 1

下面的方法創建一個在InMemoryRandomAccessStream上運行的BitmapEncoder ，添加一個從WriteableBitmap創建的SoftwareBitmap ，將流內容讀取到一個字節數組，最后將該字節數組轉換為base64字符串：

public async Task<string> ToBase64String(WriteableBitmap writableBitmap)
{
    using (var stream = new InMemoryRandomAccessStream())
    {
        var encoder = await BitmapEncoder.CreateAsync(BitmapEncoder.PngEncoderId, stream);

        encoder.SetSoftwareBitmap(SoftwareBitmap.CreateCopyFromBuffer(
            writableBitmap.PixelBuffer,
            BitmapPixelFormat.Bgra8,
            writableBitmap.PixelWidth,
            writableBitmap.PixelHeight));

        await encoder.FlushAsync();

        var bytes = new byte[stream.Size];
        await stream.AsStream().ReadAsync(bytes, 0, bytes.Length);

        return Convert.ToBase64String(bytes);
    }
}

Answer 2

如果要將圖像轉換為base64流，最好的方法是首先對其進行編碼。

public static string GetByteArrayFromImage(BitmapSource writeableBitmap)
{
    JpegBitmapEncoder encoder = new JpegBitmapEncoder();
    encoder.Frames.Add(BitmapFrame.Create(writeableBitmap));
    MemoryStream stream = new MemoryStream();
    encoder.Save(stream);
    Byte[] bytes = stream.ToArray();
    return Convert.ToBase64String(bytes);
}

public static BitmapSource GetImageFromByteArray(string base64String)
{
    byte[] bytes = Convert.FromBase64String(base64String);
    MemoryStream stream = new MemoryStream(bytes);
    JpegBitmapDecoder decoder = new JpegBitmapDecoder(stream, 
        BitmapCreateOptions.None, BitmapCacheOption.Default);
    return decoder.Frames[0];
}

測試用例以證明其有效：

BitmapImage originalImage = new BitmapImage(new Uri(@"Path to any picture", UriKind.Absolute));

string encoded = GetByteArrayFromImage(originalImage);
BitmapSource decoded = GetImageFromByteArray(encoded);

image1.Source = decoded;