Opening a File Into WriteableBitmap

Question

This is a question that I'm sure has been asked many times before, but I still have trouble finding the answer. I have a file (*.png) that I need to open as a WriteableBitmap. I have the Uri and am able to open it as a BitmapImage, but I cannot seem to create a WriteableBitmap from it. Can anybody help me here? Thanks.

Answer 1

If you have the Uri then you can use RandomAccessStreamReference.CreateFromUri to create a stream (valid chemes are http, https, ms-appx, and ms-appdata, docs here), and read from the stream to create the WriteableBitmap.

Code sample:

private async Task<WriteableBitmap> UriToWriteableBitmap(Uri uri)  
{  
    var randomAccessStreamReference = RandomAccessStreamReference.CreateFromUri(uri);  
    using (IRandomAccessStreamWithContentType stream = await randomAccessStreamReference.OpenReadAsync())  
    {  
        return await StreamToWriteableBitmap(stream);  
    }  
}  
  
private static async Task<WriteableBitmap> StreamToWriteableBitmap(IRandomAccessStream stream)  
{  
    var decoder = await BitmapDecoder.CreateAsync(stream);  
    var writeableBitmap = new WriteableBitmap((int)decoder.PixelWidth, (int)decoder.PixelHeight);  
    stream.Seek(0);  
    await writeableBitmap.SetSourceAsync(stream);  
    return writeableBitmap;  
}  

You can use method StreamToWriteableBitmap above with StorageFile too:

using (IRandomAccessStreamWithContentType stream = await storageFile.OpenReadAsync())  
{  
    WriteableBitmap streamToWriteableBitmap = await StreamToWriteableBitmap(stream);  
}  

Here below another implementation of method StreamToWriteableBitmap that uses SoftwareBitmap class

private static async Task<WriteableBitmap> StreamToWriteableBitmap(IRandomAccessStream stream)  
{  
    var decoder = await BitmapDecoder.CreateAsync(stream);  
    using (SoftwareBitmap softwareBitmap = await decoder.GetSoftwareBitmapAsync())  
    {  
        var writeableBitmap = new WriteableBitmap(softwareBitmap.PixelWidth, softwareBitmap.PixelHeight);  
        softwareBitmap.CopyToBuffer(writeableBitmap.PixelBuffer);  
        return writeableBitmap;  
    }  
}  

Answer 2

Hi,
try following demo: