GetImageSynchronousIgnoreDpi
(
String uriString
)
{
Debug.Assert(!String.IsNullOrEmpty(uriString));
AssertValid();
BitmapSource oBitmapSource = GetImageSynchronous(uriString);
if (oBitmapSource.DpiX != m_dScreenDpi)
{
// The DPI properties of BitmapSource are read-only. To work
// around this, copy the BitmapSource to a new BitmapSource,
// changing the DPI in the process. Wasteful, but there doesn't
// seem to be a better way.
// The formula for stride, which isn't documented in MSDN, was
// taken from here:
//
// http://social.msdn.microsoft.com/Forums/en/windowswic/thread/
// 8e2d2dbe-6819-488b-ac49-bf5235d87bc4
Int32 iStride = ((oBitmapSource.PixelWidth *
oBitmapSource.Format.BitsPerPixel) + 7) / 8;
// Also, see this:
//
// http://social.msdn.microsoft.com/Forums/en-US/wpf/thread/
// 56364b28-1277-4be8-8d45-78788cc4f2d7/
Byte [] abtPixels = new Byte[oBitmapSource.PixelHeight * iStride];
oBitmapSource.CopyPixels(abtPixels, iStride, 0);
oBitmapSource = BitmapSource.Create(oBitmapSource.PixelWidth,
oBitmapSource.PixelHeight, m_dScreenDpi, m_dScreenDpi,
oBitmapSource.Format, oBitmapSource.Palette, abtPixels, iStride
);
WpfGraphicsUtil.FreezeIfFreezable(oBitmapSource);
}
return(oBitmapSource);
}
GetImageSynchronousHttp
(
Uri uri
)
{
Debug.Assert(uri != null);
Debug.Assert(uri.Scheme == Uri.UriSchemeHttp ||
uri.Scheme == Uri.UriSchemeHttps);
AssertValid();
// Talk about inefficient...
//
// The following code uses HttpWebRequest to synchronously download the
// image into a List<Byte>, then passes that List as a MemoryStream to
// BitmapImage.StreamSource. It works, but it involves way too much
// Byte copying. There has to be a better way to do this, but so far I
// haven't found one.
//
// In the following post...
//
// http://stackoverflow.com/questions/426645/
// how-to-render-an-image-in-a-background-wpf-process
//
// ...the poster suggests feeding the WebResponse.GetResponseStream()
// indirectly to BitmapImage.StreamSource. This sometimes works but
// sometimes doesn't, which you can tell by checking
// BitmapImage.IsDownloading at the end of his code. It is true
// sometimes, indicating that the Bitmap is still downloading.
HttpWebRequest oHttpWebRequest = (HttpWebRequest)WebRequest.Create(uri);
oHttpWebRequest.Timeout = HttpWebRequestTimeoutMs;
oHttpWebRequest.CachePolicy = new RequestCachePolicy(
RequestCacheLevel.CacheIfAvailable);
WebResponse oWebResponse = oHttpWebRequest.GetResponse();
BinaryReader oBinaryReader = new BinaryReader(
oWebResponse.GetResponseStream());
List <Byte> oResponseBytes = new List <Byte>();
while (true)
{
Byte [] abtSomeResponseBytes = oBinaryReader.ReadBytes(8192);
if (abtSomeResponseBytes.Length == 0)
{
break;
}
oResponseBytes.AddRange(abtSomeResponseBytes);
}
Byte [] abtAllResponseBytes = oResponseBytes.ToArray();
oResponseBytes = null;
MemoryStream oMemoryStream = new MemoryStream(abtAllResponseBytes,
false);
BitmapImage oBitmapImage = new BitmapImage();
oBitmapImage.BeginInit();
oBitmapImage.StreamSource = oMemoryStream;
oBitmapImage.EndInit();
WpfGraphicsUtil.FreezeIfFreezable(oBitmapImage);
return(oBitmapImage);
}
GetImageSynchronous
(
String uriString
)
{
Debug.Assert(!String.IsNullOrEmpty(uriString));
AssertValid();
const Int32 ErrorImageWidthAndHeight = 52;
Uri oUri;
if (Uri.TryCreate(uriString, UriKind.Absolute, out oUri))
{
if (oUri.Scheme == Uri.UriSchemeHttp ||
oUri.Scheme == Uri.UriSchemeHttps)
{
try
{
return(GetImageSynchronousHttp(oUri));
}
catch (WebException)
{
// (These empty catch blocks cause an error image to be
// returned.)
}
catch (ArgumentException)
{
/*
* Attempting to download a possibly corrupt image from this
* Twitter URL:
*
* http://a1.twimg.com/profile_images/1112245377/
* Photo_on_2010-08-27_at_18.51_normal.jpg
*
* raised the following exception:
*
* [ArgumentException]: An invalid character was found in text
* content.
* at System.Windows.Media.Imaging.BitmapFrameDecode.
* get_ColorContexts()
* at System.Windows.Media.Imaging.BitmapImage.
* FinalizeCreation()
* at System.Windows.Media.Imaging.BitmapImage.EndInit()
*/
}
catch (IOException)
{
/*
* Attempting to download a possibly corrupt image from this
* Twitter URL:
*
* http://a2.twimg.com/profile_images/1126755034/
* 8FjbVD_normal.gif
*
* raised the following exception:
*
* [IOException]: Cannot read from the stream.
* [COMException]: Exception from HRESULT: 0x88982F72
* at System.Windows.Media.Imaging.BitmapDecoder.
* SetupDecoderFromUriOrStream(Uri uri, Stream stream,
* BitmapCacheOption cacheOption, Guid& clsId, Boolean&
* isOriginalWritable, Stream& uriStream,
* UnmanagedMemoryStream& unmanagedMemoryStream,
* SafeFileHandle& safeFilehandle)
* ...
*/
}
catch (NotSupportedException)
{
/*
* Attempting to download a possibly corrupt image from a
* Twitter URL (didn't record the URL) raised the following
* exception:
*
* [NotSupportedException]: No imaging component suitable
* to complete this operation was found.
*/
}
}
else if (oUri.Scheme == Uri.UriSchemeFile)
{
try
{
BitmapImage oBitmapImage = new BitmapImage(oUri);
WpfGraphicsUtil.FreezeIfFreezable(oBitmapImage);
return(oBitmapImage);
}
catch (IOException)
{
}
catch (NotSupportedException)
{
// Invalid image file.
}
catch (UnauthorizedAccessException)
{
// The URI is actually a folder, for example.
}
}
}
if (m_oCachedErrorImage == null)
{
m_oCachedErrorImage = CreateErrorImage(ErrorImageWidthAndHeight);
}
return(m_oCachedErrorImage);
}
