c# - 不支持位图编码器保存

Question

我有以下代码，我看不出有什么问题，关于问题可能是什么的任何想法？

private static string SaveBaseImage( ZipArchive arc, DBImage image, int imageIndex )
{
    using (var mem = new MemoryStream(image.Data))
    {
        var bmp = BitmapFrame.Create(mem);
        //var bmp = BitmapFrame.Create(m‌​em, BitmapCreateOptions.‌​None, BitmapCacheOption.On‌​Load);
        var codex = bmp.Decoder.CodecInfo;

        var filename = $"{imageIndex}{codex.FileExtensions}";
        var imagezip = arc.CreateEntry(filename,CompressionLevel.Optimal));
        using (var imagestream = imagezip.Open())
        {
            SaveImage( bmp, imagestream);
        }
        return filename;
    }
}

private static void SaveImage(BitmapFrame data, Stream saveStream)
{
    var codex = data.Decoder.CodecInfo;
    var encoder = BitmapEncoder.Create(codex.ContainerFormat);
    encoder.Frames.Add(data);
    encoder.Save(saveStream);
}

当我运行它抛出

System.NotSupportedException occurred HResult=-2146233067

Message=Specified method is not supported. Source=PresentationCore

StackTrace: at System.Windows.Media.Imaging.BitmapEncoder.Save(Stream stream) at FileFormatters.Export.SaveImage(BitmapFrame data, Stream saveStream)

InnerException: null

MSDN页面说

NotSupportedException :The Frames value that is passed to the encoder is null.

NotSupportedException :The Frames count is less than or equal to zero.

但是帧数为 1 并且数据不为空

更多信息

arc declared as using (ZipArchive arc = new ZipArchive(stream, ZipArchiveMode.Create))
image.Data is byte[]
codex.FriendlyName = "PNG Decoder"
encoder.CodecInfo.FriendlyName = "PNG Encoder"

Answer 1

似乎有必要将图像缓冲区写入中间 MemoryStream，然后才能将其写入 ZipEntry Stream:

private static void SaveImage(BitmapFrame data, Stream saveStream)
{
    var encoder = BitmapEncoder.Create(data.Decoder.CodecInfo.ContainerFormat);
    encoder.Frames.Add(data);

    using (var memoryStream = new MemoryStream())
    {
        encoder.Save(memoryStream);
        memoryStream.Position = 0;
        memoryStream.CopyTo(saveStream);
    }
}