如何使用c＃将图像转换为Windows Phone 8.1中的字节数组

Question

I am using this code

MemoryStream ms = new MemoryStream();
WriteableBitmap wb = new WriteableBitmap(myimage);
wb.SaveJpeg(ms, myimage.PixelWidth, myimage.PixelHeight, 0, 100);
byte [] imageBytes = ms.ToArray();

from Convert image to byte array on Windows Phone 7 No System.Drawing Dll any other way? but WriteableBitmap does not contain SaveJpeg method in Windows phone 8.1 environment.

Answer 1

On Windows Phone 8.1 Silverlight applications your code works fine, I assume that myImage is a BitmapImage . The only thing just must do is to wait for the BitmapImage to load completly:

using System.IO;
using System.Windows.Media.Imaging;
...
myImage = new BitmapImage(new Uri("http://i.stack.imgur.com/830Ke.jpg?s=128&g=1", UriKind.Absolute));
myImage.CreateOptions = BitmapCreateOptions.None;
myImage.ImageOpened += myImage_ImageOpened;
...
void myImage_ImageOpened(object sender, RoutedEventArgs e)
{
    MemoryStream ms = new MemoryStream();
    WriteableBitmap wb = new WriteableBitmap(myImage);
    wb.SaveJpeg(ms, myImage.PixelWidth, myImage.PixelHeight, 0, 100);
    byte[] imageBytes = ms.ToArray();
}

I just tested that code and it works perfectly on WP8.1.

But as you commented on another post you can't reference Microsoft.Phone , you are probably doing a Windows Phone 8.1 Store App, in which case you can use the following code:

using Windows.UI.Xaml.Media.Imaging;
using Windows.Storage.Streams;
using System.Runtime.InteropServices.WindowsRuntime;
...
BitmapImage bitmapImage = new BitmapImage(new Uri("http://i.stack.imgur.com/830Ke.jpg?s=128&g=1"));
RandomAccessStreamReference rasr = RandomAccessStreamReference.CreateFromUri(bitmapImage.UriSource);
var streamWithContent = await rasr.OpenReadAsync();
byte[] buffer = new byte[streamWithContent.Size];
await streamWithContent.ReadAsync(buffer.AsBuffer(), (uint)streamWithContent.Size, InputStreamOptions.None);

Answer 2

I suspect that you are targeting Windows Runtime Apps as you haven't found the namespace suggested in this answer (which will work for WP8.1 Silverlight) .

In Windows Runtime apps you can use Encoder - the sample code can look like this:

// lets assume that you have your image in WriteableBitmap yourWb
using (MemoryStream ms = new MemoryStream())
{
    var encoder = await BitmapEncoder.CreateAsync(BitmapEncoder.PngEncoderId, ms.AsRandomAccessStream());
    encoder.SetPixelData(BitmapPixelFormat.Bgra8,
        BitmapAlphaMode.Ignore,
        imageWidth,
        imageHeight,
        horizontalDPI,
        verticalDPI,
        yourWb.PixelBuffer.ToArray());

    await encoder.FlushAsync();
}

Answer 3

SaveJpeg is an extension method ( http://msdn.microsoft.com/en-US/library/windowsphone/develop/system.windows.media.imaging.extensions.savejpeg(v=vs.105).aspx ). Have you referenced Microsoft.Phone in your project references and added using System.Windows.Media.Imaging; to your .cs file?