Show signature from byte array on canvas

Question

Hello everyone,

 I am trying to draw a signature on canvas from byte array. Here is my code. When i am run this code, this error is come:

Error HRESULT E_FAIL has been returned from a call to a COM component.

Here is my code:

//strbase64 is base64 string

Byte[] ByteOutput = System.Text.Encoding.UTF8.GetBytes(strbase64);

            using (var stream2 = new InMemoryRandomAccessStream())
            {
                await stream2.WriteAsync(ByteOutput.AsBuffer());
                await stream2.FlushAsync();
                stream2.Seek(0);
                await _inkManager.LoadAsync(stream2);
                if (_inkManager.GetStrokes().Count > 0)
                {
                    RenderStrokes();
                }

Answer 1

Where do you get the exception?

What is strbase64? Where does it come from and are you sure it is a valid ISF file?

--Rob

Answer 2

Hello Rob, 

strbase64 is base64 string, and exception comes at This line:

await _inkManager.LoadAsync(stream2);

Answer 3

Try this.

Byte[] ByteOutput = System.Text.Encoding.UTF8.GetBytes(strbase64);
MemoryStream stream = new MemoryStream(ByteOutput);
var randomAccessStream = new MemoryRandomAccessStream(stream);
await _inkManager.LoadAsync(randomAccessStream); 

MemoryRandomAccessStream class is available here.

public class MemoryRandomAccessStream : IRandomAccessStream
{
    private Stream m_InternalStream;

    public MemoryRandomAccessStream(Stream stream)
    {
        this.m_InternalStream = stream;
    }

    public MemoryRandomAccessStream(byte[] bytes)
    {
        this.m_InternalStream = new MemoryStream(bytes);
    }

    public IInputStream GetInputStreamAt(ulong position)
    {
        this.m_InternalStream.Seek((long)position, SeekOrigin.Begin);

        return this.m_InternalStream.AsInputStream();
    }

    public IOutputStream GetOutputStreamAt(ulong position)
    {
        this.m_InternalStream.Seek((long)position, SeekOrigin.Begin);

        return this.m_InternalStream.AsOutputStream();
    }

    public ulong Size
    {
        get { return (ulong)this.m_InternalStream.Length; }
        set { this.m_InternalStream.SetLength((long)value); }
    }

    public bool CanRead
    {
        get { return true; }
    }

    public bool CanWrite
    {
        get { return true; }
    }

    public IRandomAccessStream CloneStream()
    {
        throw new NotSupportedException();
    }

    public ulong Position
    {
        get { return (ulong)this.m_InternalStream.Position; }
    }

    public void Seek(ulong position)
    {
        this.m_InternalStream.Seek((long)position, 0);
    }

    public void Dispose()
    {
        this.m_InternalStream.Dispose();
    }

    public Windows.Foundation.IAsyncOperationWithProgress<IBuffer, uint> ReadAsync(IBuffer buffer, uint count, InputStreamOptions options)
    {
        var inputStream = this.GetInputStreamAt(0);
        return inputStream.ReadAsync(buffer, count, options);
    }

    public Windows.Foundation.IAsyncOperation<bool> FlushAsync()
    {
        var outputStream = this.GetOutputStreamAt(0);
        return outputStream.FlushAsync();
    }

    public Windows.Foundation.IAsyncOperationWithProgress<uint, uint> WriteAsync(IBuffer buffer)
    {
        var outputStream = this.GetOutputStreamAt(0);
        return outputStream.WriteAsync(buffer);
    }
}

Answer 4

I have another problem, 

how to convert ioutputstream to bytearray, my code:

 Windows.Storage.Pickers.FileSavePicker save = new Windows.Storage.Pickers.FileSavePicker();
                save.SuggestedStartLocation = Windows.Storage.Pickers.PickerLocationId.PicturesLibrary;
                save.DefaultFileExtension = ".png";
                save.FileTypeChoices.Add("PNG", new string[] { ".png" });
                StorageFile filesave = await save.PickSaveFileAsync();
                IOutputStream ab = await filesave.OpenAsync(FileAccessMode.ReadWrite);

Answer 5

I successful solved my problem. There is an error during convert outputstream to byte array.