MapTileBitmapRequest.PixelData Propriété

Définition

Espace de noms:

Windows.UI.Xaml.Controls.Maps

Obtient les données bitmap pour CustomMapTileDataSource.

public:
 property IRandomAccessStreamReference ^ PixelData { IRandomAccessStreamReference ^ get(); void set(IRandomAccessStreamReference ^ value); };

IRandomAccessStreamReference PixelData();

void PixelData(IRandomAccessStreamReference value);

public IRandomAccessStreamReference PixelData { get; set; }

var iRandomAccessStreamReference = mapTileBitmapRequest.pixelData;
mapTileBitmapRequest.pixelData = iRandomAccessStreamReference;

Public Property PixelData As IRandomAccessStreamReference

Valeur de propriété

IRandomAccessStreamReference

Données bitmap.

Remarques

CustomMapTileDataSource prend en charge le dessin de vignettes en mémoire et leur retour sous forme de flux de pixels. L’exemple de code suivant illustre une approche pour dessiner des vignettes en mémoire.

// Create new custom tile source
CustomMapTileDataSource customDataSource = new CustomMapTileDataSource();
customDataSource.BitmapRequested += customDataSource_BitmapRequestedAsync;
customTileSource = new MapTileSource(customDataSource);

/// <summary>
/// BitmapRequested event handler for CustomMapTileDataSource.BitmapRequested event
/// </summary>
/// <param name="sender">sender</param>
/// <param name="args">args for ZoomLevel, X, Y and the PixelData</param>
private async void customDataSource_BitmapRequestedAsync(CustomMapTileDataSource sender, MapTileBitmapRequestedEventArgs args)
{
    var deferral = args.Request.GetDeferral();
    args.Request.PixelData = await CreateBitmapAsStreamAsync();
    deferral.Complete();
}

/// <summary>
/// Create memory buffer with length of 256 * 256 * 4.  
/// This memory buffer is holding 256 * 256 pixels
/// </summary>
/// <returns>memory buffer that fills with red opaque pixels.</returns>
private async Task<Windows.Storage.Streams.RandomAccessStreamReference> CreateBitmapAsStreamAsync()
{
    int pixelHeight = 256;
    int pixelWidth = 256;
    int bpp = 4;

    byte[] bytes = new byte[pixelHeight * pixelWidth * bpp];

    for (int y = 0; y < pixelHeight; y++)
    {
        for (int x = 0; x < pixelWidth; x++)
        {
            int pixelIndex = y * pixelWidth + x;
            int byteIndex = pixelIndex * bpp;

            bytes[byteIndex] = 0xff;        // Red
            bytes[byteIndex + 1] = 0x00;    // Green
            bytes[byteIndex + 2] = 0x00;    // Blue
            bytes[byteIndex + 3] = 0x80;    // Alpha (0xff = fully opaque)
        }
    }

    // Create RandomAccessStream from byte array
    InMemoryRandomAccessStream randomAccessStream = new InMemoryRandomAccessStream();
    IOutputStream outputStream = randomAccessStream.GetOutputStreamAt(0);
    DataWriter writer = new DataWriter(outputStream);
    writer.WriteBytes(bytes);
    await writer.StoreAsync();
    await writer.FlushAsync();
    return RandomAccessStreamReference.CreateFromStream(randomAccessStream);
}

Windows::Foundation::IAsyncOperation<Windows::Storage::Streams::InMemoryRandomAccessStream> TileSources::CustomRandomAccessStreamAsync()
{
    const int pixelHeight{ 256 };
    const int pixelWidth{ 256 };
    const int bpp{ 4 };

    std::array<byte, pixelHeight * pixelWidth * bpp> bytes;

    for (int y = 0; y < pixelHeight; ++y)
    {
        for (int x = 0; x < pixelWidth; ++x)
        {
            int pixelIndex = y * pixelWidth + x;
            int byteIndex = pixelIndex * bpp;

            // Set current pixel bytes
            bytes[byteIndex] = (byte)(std::rand() % 256);        // Red
            bytes[byteIndex + 1] = (byte)(std::rand() % 256);    // Green
            bytes[byteIndex + 2] = (byte)(std::rand() % 256);    // Blue
            bytes[byteIndex + 3] = (byte)((std::rand() % 56) + 200);    // Alpha (0xff = fully opaque)
        }
    }

    // Create RandomAccessStream from byte array
    Windows::Storage::Streams::InMemoryRandomAccessStream randomAccessStream;
    Windows::Storage::Streams::IOutputStream outputStream{ randomAccessStream.GetOutputStreamAt(0) };
    Windows::Storage::Streams::DataWriter writer{ outputStream };
    writer.WriteBytes(bytes);

    co_await writer.StoreAsync();
    co_await writer.FlushAsync();

    co_return randomAccessStream;
}

InMemoryRandomAccessStream^ TileSources::CustomRandomAccessStream::get()
{
       int pixelHeight = 256;
       int pixelWidth = 256;
       int bpp = 4;

       Array<byte>^ bytes = ref new Array<byte>(pixelHeight * pixelWidth * bpp);

       for (int y = 0; y < pixelHeight; y++)
       {
              for (int x = 0; x < pixelWidth; x++)
              {
                     int pixelIndex = y * pixelWidth + x;
                     int byteIndex = pixelIndex * bpp;

                     // Set current pixel bytes
                     bytes[byteIndex] = (byte)(std::rand() % 256);        // Red
                     bytes[byteIndex + 1] = (byte)(std::rand() % 256);    // Green
                     bytes[byteIndex + 2] = (byte)(std::rand() % 256);    // Blue
                     bytes[byteIndex + 3] = (byte)((std::rand() % 56) + 200);    // Alpha (0xff = fully opaque)
              }
       }

       // Create RandomAccessStream from byte array
       InMemoryRandomAccessStream^ randomAccessStream = ref new InMemoryRandomAccessStream();
       IOutputStream^ outputStream = randomAccessStream->GetOutputStreamAt(0);
       DataWriter^ writer = ref new DataWriter(outputStream);
       writer->WriteBytes(bytes);

       create_task(writer->StoreAsync()).then([writer](unsigned int)
       {
              create_task(writer->FlushAsync());
       });

       return randomAccessStream;
}

Voir aussi

• Superposer des images sous forme de vignettes sur une carte