Compress and save base64 image on Windows Phone 8.1

Question

I have implemented the following solution to compress a base 64 image and get back the new base 64 string. It works fine in Windows Phone 8.0 but targeting Windows Phone 8.1

Answer 1

In WP8.1 Runtime I've used BitmapPropertySet to define a level of compression. Here below is sample code operating on Streams:

/// 

/// Method compressing image stored in stream
/// 
/// stream with the image
/// new quality of the image 0.0 - 1.0
/// 
private async Task CompressImageAsync(IRandomAccessStream sourceStream, double newQuality)
{
    // create bitmap decoder from source stream
    BitmapDecoder bmpDecoder = await BitmapDecoder.CreateAsync(sourceStream);

    // bitmap transform if you need any
    BitmapTransform bmpTransform = new BitmapTransform() { ScaledHeight = newHeight, ScaledWidth = newWidth, InterpolationMode = BitmapInterpolationMode.Cubic };

    PixelDataProvider pixelData = await bmpDecoder.GetPixelDataAsync(BitmapPixelFormat.Rgba8, BitmapAlphaMode.Straight, bmpTransform, ExifOrientationMode.RespectExifOrientation, ColorManagementMode.DoNotColorManage);
    InMemoryRandomAccessStream destStream = new InMemoryRandomAccessStream(); // destination stream

    // define new quality for the image
    var propertySet = new BitmapPropertySet();
    var quality = new BitmapTypedValue(newQuality, PropertyType.Single);
    propertySet.Add("ImageQuality", quality);

    // create encoder with desired quality
    BitmapEncoder bmpEncoder = await BitmapEncoder.CreateAsync(BitmapEncoder.JpegEncoderId, destFileStream, propertySet);
    bmpEncoder.SetPixelData(BitmapPixelFormat.Rgba8, BitmapAlphaMode.Straight, newHeight, newWidth, 300, 300, pixelData.DetachPixelData());
    await bmpEncoder.FlushAsync();
    return destStream;
}