Windows 8 如何在WinJS中显示Windows.Graphics.Imaging.BitmapDecoder？

我正在尝试制作一款应用过滤效果的应用程序。从FilePicker我可以得到一个IRandomaccesstream，我可以把它转换成位图解码器。但我不知道如何将位图数据显示为图像？我不想使用文件名或路径，只想将位图数据显示为图像。我应该在WinJS中使用什么控件以及如何使用它？

使用

MSApp.createStreamFromInputStream（）

和

URL.createObjectURL（）

将IIInputStream或IRandomAccessStream转换为图像：

HTML应该如下所示：

<img id="theImage" src="#" />

---

这些MSDN博客更详细地解释了以下过程 http://goo.gl/OLgfn

我找到了一种从位图解码器创建位图编码器的方法。该编码器可用于创建可在字段中显示的内存流

       internal async Task<InMemoryRandomAccessStream> applyFilterInternal()
    {
        inputStream = await file.OpenAsync(Windows.Storage.FileAccessMode.ReadWrite);
        decoder = await Windows.Graphics.Imaging.BitmapDecoder.CreateAsync(inputStream);

        var memStream = new Windows.Storage.Streams.InMemoryRandomAccessStream();
        var encoder = await Windows.Graphics.Imaging.BitmapEncoder.CreateForTranscodingAsync(memStream, decoder);

        encoder.BitmapTransform.ScaledWidth = 640;
        encoder.BitmapTransform.ScaledHeight = 480;
        encoder.BitmapTransform.Rotation = Windows.Graphics.Imaging.BitmapRotation.Clockwise90Degrees;

        // Fant is a relatively high quality interpolation algorithm.
        encoder.BitmapTransform.InterpolationMode = Windows.Graphics.Imaging.BitmapInterpolationMode.Fant;

        // Attempt to generate a new thumbnail from the updated pixel data.
        // Note: Only JPEG, TIFF and JPEG-XR images support encoding thumbnails.
        encoder.IsThumbnailGenerated = true;

        await encoder.FlushAsync();
        return memStream;
    }

public IAsyncOperation<InMemoryRandomAccessStream> applyFilter()
    {
        Task<InMemoryRandomAccessStream> from = applyFilterInternal();
        IAsyncOperation<InMemoryRandomAccessStream> to = from.AsAsyncOperation();
        return to;
    }

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Kiewic，我感谢你的回答。但我面临的实际问题是，我需要从BitmapDecoder对象中提取IRandomAccessStream。我尝试了提供的几种方法，但我无法做到这一点。

       internal async Task<InMemoryRandomAccessStream> applyFilterInternal()
    {
        inputStream = await file.OpenAsync(Windows.Storage.FileAccessMode.ReadWrite);
        decoder = await Windows.Graphics.Imaging.BitmapDecoder.CreateAsync(inputStream);

        var memStream = new Windows.Storage.Streams.InMemoryRandomAccessStream();
        var encoder = await Windows.Graphics.Imaging.BitmapEncoder.CreateForTranscodingAsync(memStream, decoder);

        encoder.BitmapTransform.ScaledWidth = 640;
        encoder.BitmapTransform.ScaledHeight = 480;
        encoder.BitmapTransform.Rotation = Windows.Graphics.Imaging.BitmapRotation.Clockwise90Degrees;

        // Fant is a relatively high quality interpolation algorithm.
        encoder.BitmapTransform.InterpolationMode = Windows.Graphics.Imaging.BitmapInterpolationMode.Fant;

        // Attempt to generate a new thumbnail from the updated pixel data.
        // Note: Only JPEG, TIFF and JPEG-XR images support encoding thumbnails.
        encoder.IsThumbnailGenerated = true;

        await encoder.FlushAsync();
        return memStream;
    }

public IAsyncOperation<InMemoryRandomAccessStream> applyFilter()
    {
        Task<InMemoryRandomAccessStream> from = applyFilterInternal();
        IAsyncOperation<InMemoryRandomAccessStream> to = from.AsAsyncOperation();
        return to;
    }

            filter.applyFilter().then(function (memStream) {
            var msStream = MSApp.createStreamFromInputStream("image/jpeg", memStream);
            var imageURL = URL.createObjectURL(msStream);
            id("imageInput").src = imageURL;

        });