I have a problem with saving an image (or a bitmapImage or a PhotoResult) to a byte[] and then converting it back to an image.
I found a lot of posts on the internet about it but they dont work. In this code I got an Unspecifed error when I do this: SetSource ( bitmapImage.SetSource(ms);) and dont know how to do that.
I also want to make a list of Devices (each with a name, id, status and an image which I will represent as a byte[]) and save it to IsolatedStorage, and then read it and list them (with an image of course.)
Here is some code I have so far:
public void photoChooserTask_Completed(object sender, PhotoResult e)
{
if (e.TaskResult == TaskResult.OK)
{
imageBytes = new byte[e.ChosenPhoto.Length];
e.ChosenPhoto.Read(imageBytes, 0, imageBytes.Length);
BitmapImage bitmapImage = new BitmapImage();
MemoryStream ms = new MemoryStream(imageBytes);
try
{
bitmapImage.SetSource(ms);
}
catch (Exception ea)
{
//
}
image1.Source = bitmapImage;
}
Have you tried the Microsoft.Phone.PictureDecoder class? It has a DecodeJpeg function that returns an instance of a WritableBitmap object.
Another solution is to use the WritableBitmapEx extension library that makes digital image processing much easier and has a very good performance. The function you need is called FromByteArray.
In both cases you'll have to use a WriteableBitmap, because BitmapImage is protected from modification. Since both BitmapImage and WriteableBitmap are subclasses of BitmapSource, you can easily display them in the image control.
Hope it helps!
Related
In an windows phone 7 application I'm populating one listbox with remote images .. since the images are not downloaded instantly I want to load a default image until the remote image are ready. What is the best way to do this?
Until now, I have the following code skelton:
public partial class RemoteImage : PhoneApplicationPage
{
ObservableCollection<Image> images = new ObservableCollection<Image> { };
public RemoteImage()
{
InitializeComponent();
listImage.ItemsSource = GetAllImages();
}
private ImageSource GetImageSource(string fileName)
{
return new BitmapImage(new Uri(fileName, UriKind.Absolute));
}
private ObservableCollection<Image> GetAllImages()
{
WebClient restClient = new WebClient();
restClient.OpenReadAsync(new Uri(#"http://www.my-api.com"));
restClient.OpenReadCompleted += new OpenReadCompletedEventHandler(onReadComplete);
return images;
}
private void onReadComplete(object sender, OpenReadCompletedEventArgs args)
{
Stream stm = args.Result;
DataContractJsonSerializer ser = new DataContractJsonSerializer(typeof(RootObject));
RootObject ro = (RootObject)ser.ReadObject(stm);
foreach (var item in ro.items)
{
images.Add(new Image{ PhotoSource = GetImageSource(item.image.link) });
}
}
}
If you know, how many images you would need, you should create first the number of default images. Load some image file directly at your project and use it as imageSource for default images. Then, when you'll finish downloading remote images, you should set the new image source for each.
When I got the similar issue, I had some problems with defining which exactly downloaded image refers to which object on page. (As you remember the WebClient objects work asynchronously, so if you have 10 images on page and download 10 remote images at once you can't say that the first downloaded image is the first on page) To solve this you could create more complicated download method (I used a delegate to transfer the id/name of image) or use recursion (Start download method for first image, download it, set source for one on page, download next one...).
I'm receiving byte[] image-data (from a webcam source, transmitted over network) and want to display it in my WPF Image control.
If I set the resolution to 160x120, I see a nice tiny image being displayed.
For any other resolution though I see nada, nothing, zilch, squat.
If I write the raw bytes to disk I can see that the data is indeed a valid jpg-image.
Just to make sure it's not jpeg-incompatibility I've tested it with png- and bmp-encoding/decoding as well with the same results; still no image.
Anyone got a bright idea ?
private bool OnImage(byte[] inJpg)
{
this.Dispatch(() =>
{
//File.WriteAllBytes("h:\\tmp\\test" + sImageNum++ + ".jpg", inJpg);
using (MemoryStream ms = new MemoryStream(inJpg))
{
BitmapDecoder decoder = new JpegBitmapDecoder(ms, BitmapCreateOptions.None, BitmapCacheOption.Default);
ImageRemoteVideo.Source = decoder.Frames[0];
}
}
);
}
Assuming ImageRemoteVideo is an instance of a WPF Image control, you may be getting bit by some lazy resolve issues. The Image control has "BeginInit" and "EndInit" methods that you should probably be using. Put the BeginInit method before you set the stream, the other after you set it. Also, if I remember right, the Image class supports a StreamSource. You could try setting your MemoryStream (without disposing of it and without using the JpegBitmapDecoder) to that Property. If that works, then see if you can dispose it after the EndInit call.
I have just found a way to make it work, but I'd love it if someone can explain WHY it works :)
First off, I'm using the raw bytestream to create a BitmapImage.
BUT - if I use a "using" clause around the MemoryStream it doesn't work, if I don't it works.
So this doesn't work :
using (MemoryStream byteStream = new MemoryStream(inJpg))
{
BitmapImage image = new BitmapImage();
image.BeginInit();
image.StreamSource = byteStream;
image.EndInit();
ImageRemoteVideo.Source = image;
}
But this does :
MemoryStream byteStream = new MemoryStream(inJpg);
BitmapImage image = new BitmapImage();
image.BeginInit();
image.StreamSource = byteStream;
image.EndInit();
ImageRemoteVideo.Source = image;
Found it. It's like Brannon said a case of delayed loading.
Specifying "CacheOption = BitmapCacheOption.OnLoad;" fixes it !
Cheers !
Working version :
MemoryStream byteStream = new MemoryStream(inJpg);
{
BitmapImage image = new BitmapImage();
image.BeginInit();
image.StreamSource = byteStream;
image.CacheOption = BitmapCacheOption.OnLoad;
image.EndInit();
ImageRemoteVideo.BeginInit();
ImageRemoteVideo.Source = image;
ImageRemoteVideo.EndInit();
}
There are a bunch of questions about this already on this site and other forums, but I've yet to find a solution that actually works.
Here's what I want to do:
In my WPF app, I want to load an image.
The image is from an arbitrary URI on the web.
The image could be in any format.
If I load the same image more than once, I want to use the standard windows internet cache.
Image loading and decoding should happen synchronously, but not on the UI Thread.
In the end I should end up with something that I can apply to an <Image>'s source property.
Things I have tried:
Using WebClient.OpenRead() on a BackgroundWorker. Works fine, but doesn't use the cache. WebClient.CachePolicy only affects that particular WebClient instance.
Using WebRequest on the Backgroundworker instead of WebClient, and setting WebRequest.DefaultCachePolicy. This uses the cache properly, but I've not seen an example that doesn't give me corrupted-looking images half the time.
Creating a BitmapImage in a BackgroundWorker, setting BitmapImage.UriSource and trying to handle BitmapImage.DownloadCompleted. This seems to use the cache if BitmapImage.CacheOption is set, but there doesn't seem to be away to handle DownloadCompleted since the BackgroundWorker returns immediately.
I've been struggling with this off-and-on for literally months and I'm starting to think it's impossible, but you're probably smarter than me. What do you think?
I have approached this problem in several ways, including with WebClient and just with BitmapImage.
EDIT: Original suggestion was to use the BitmapImage(Uri, RequestCachePolicy) constructor, but I realized my project where I tested this method was only using local files, not web. Changing guidance to use my other tested web technique.
You should run the download and decoding on a background thread because during loading, whether synchronous or after download the image, there is a small but significant time required to decode the image. If you are loading many images, this can cause the UI thread to stall. (There are a few other intricacies here like DelayCreation but they don't apply to your question.)
There are a couple ways to load an image, but I've found for loading from the web in a BackgroundWorker, you'll need to download the data yourself using WebClient or a similar class.
Note that BitmapImage internally uses a WebClient, plus it has a lot of error handling and settings of credentials and other things that we'd have to figure out for different situations. I'm providing this snippet but it has only been tested in a limited number of situations. If you are dealing with proxies, credentials, or other scenarios you'll have to massage this a bit.
BackgroundWorker worker = new BackgroundWorker();
worker.DoWork += (s, e) =>
{
Uri uri = e.Argument as Uri;
using (WebClient webClient = new WebClient())
{
webClient.Proxy = null; //avoids dynamic proxy discovery delay
webClient.CachePolicy = new RequestCachePolicy(RequestCacheLevel.Default);
try
{
byte[] imageBytes = null;
imageBytes = webClient.DownloadData(uri);
if (imageBytes == null)
{
e.Result = null;
return;
}
MemoryStream imageStream = new MemoryStream(imageBytes);
BitmapImage image = new BitmapImage();
image.BeginInit();
image.StreamSource = imageStream;
image.CacheOption = BitmapCacheOption.OnLoad;
image.EndInit();
image.Freeze();
imageStream.Close();
e.Result = image;
}
catch (WebException ex)
{
//do something to report the exception
e.Result = ex;
}
}
};
worker.RunWorkerCompleted += (s, e) =>
{
BitmapImage bitmapImage = e.Result as BitmapImage;
if (bitmapImage != null)
{
myImage.Source = bitmapImage;
}
worker.Dispose();
};
worker.RunWorkerAsync(imageUri);
I tested this in a simple project and it works fine. I'm not 100% about whether it is hitting the cache, but from what I could tell from MSDN, other forum questions, and Reflectoring into PresentationCore it should be hitting the cache. WebClient wraps WebRequest, which wraps HTTPWebRequest, and so on, and the cache settings are passed down each layer.
The BitmapImage BeginInit/EndInit pair ensures that you can set the settings you need at the same time and then during EndInit it executes. If you need to set any other properties, you should use the empty constructor and write out the BeginInit/EndInit pair like above, setting what you need before calling EndInit.
I typically also set this option, which forces it to load the image into memory during EndInit:
image.CacheOption = BitmapCacheOption.OnLoad;
This will trade off possible higher memory usage for better runtime performance. If you do this, then the BitmapImage will be loaded synchronously within EndInit, unless the BitmapImage requires async downloading from a URL.
Further notes:
BitmapImage will async download if the UriSource is an absolute Uri and is an http or https scheme. You can tell whether it is downloading by checking the BitmapImage.IsDownloading property after EndInit. There are DownloadCompleted, DownloadFailed, and DownloadProgress events, but you have to be extra tricky to get them to fire on the background thread. Since BitmapImage only exposes an asynchronous approach, you would have to add a while loop with the WPF equivalent of DoEvents() to keep the thread alive until the download is complete. This thread shows code for DoEvents that works in this snippet:
worker.DoWork += (s, e) =>
{
Uri uri = e.Argument as Uri;
BitmapImage image = new BitmapImage();
image.BeginInit();
image.UriSource = uri;
image.CacheOption = BitmapCacheOption.OnLoad;
image.UriCachePolicy = new RequestCachePolicy(RequestCacheLevel.Default);
image.EndInit();
while (image.IsDownloading)
{
DoEvents(); //Method from thread linked above
}
image.Freeze();
e.Result = image;
};
While the above approach works, it has a code smell because of DoEvents(), and it doesn't let you configure the WebClient proxy or other things that might help with better performance. The first example above is recommended over this one.
The BitmapImage needs async support for all of its events and internals. Calling Dispatcher.Run() on the background thread will...well run the dispatcher for the thread. (BitmapImage inherits from DispatcherObject so it needs a dispatcher. If the thread that created the BitmapImage doesn't already have a dispatcher a new one will be created on demand. cool.).
Important safety tip: The BitmapImage will NOT raise any events if it is pulling data from cache (rats).
This has been working very well for me....
var worker = new BackgroundWorker() { WorkerReportsProgress = true };
// DoWork runs on a brackground thread...no thouchy uiy.
worker.DoWork += (sender, args) =>
{
var uri = args.Argument as Uri;
var image = new BitmapImage();
image.BeginInit();
image.DownloadProgress += (s, e) => worker.ReportProgress(e.Progress);
image.DownloadFailed += (s, e) => Dispatcher.CurrentDispatcher.InvokeShutdown();
image.DecodeFailed += (s, e) => Dispatcher.CurrentDispatcher.InvokeShutdown();
image.DownloadCompleted += (s, e) =>
{
image.Freeze();
args.Result = image;
Dispatcher.CurrentDispatcher.InvokeShutdown();
};
image.UriSource = uri;
image.EndInit();
// !!! if IsDownloading == false the image is cached and NO events will fire !!!
if (image.IsDownloading == false)
{
image.Freeze();
args.Result = image;
}
else
{
// block until InvokeShutdown() is called.
Dispatcher.Run();
}
};
// ProgressChanged runs on the UI thread
worker.ProgressChanged += (s, args) => progressBar.Value = args.ProgressPercentage;
// RunWorkerCompleted runs on the UI thread
worker.RunWorkerCompleted += (s, args) =>
{
if (args.Error == null)
{
uiImage.Source = args.Result as BitmapImage;
}
};
var imageUri = new Uri(#"http://farm6.static.flickr.com/5204/5275574073_1c5b004117_b.jpg");
worker.RunWorkerAsync(imageUri);
so I have this function which gets called multiple times during my program.
//global variable
BitmapImage img;
private void LoadImageFile(string ImageName)
{
WebClient ImageClient = new WebClient();
ImageClient.DownloadStringCompleted += new DownloadStringCompletedEventHandler(ImageFileLoaded);
xmlClient.DownloadStringAsync(new Uri("/images/"+ImageName, UriKind.RelativeOrAbsolute));
}
void ImageFileLoaded(object sender, DownloadStringCompletedEventArgs e)
{
if (e.Error == null)
{
img.set = e.Result;
}
}
the following code uses the new value of "img" so I want it to start only after img has been assigned the new source but it seems that it runs before that happens
You want to use WebClient.OpenReadAsync() instead of WebClient.DownloadStringAsync() because you want to read a binary image, not a string.
Then when you get the stream, you call BitmapImage.SetSource() using that stream.
I would check out this blog by Jeremy Likness.
It uses corountines to help organise async requests. I have used this approach and have dealt with similar issues where I want actions to occur after several async tasks.
In WPF, the System.Windows.Clipboard.getImage() function returns a BitmapSource object. As a newbie in WPF coming from a WinForms background, its not clear to me how to save this image to a file. What are the steps I must take?
You need to use an encoder (subclass of BitmapEncoder). For instance, to save it to the PNG format, you do something like that :
public static void SaveClipboardImageToFile(string filePath)
{
var image = Clipboard.GetImage();
using (var fileStream = new FileStream(filePath, FileMode.Create))
{
BitmapEncoder encoder = new PngBitmapEncoder();
encoder.Frames.Add(BitmapFrame.Create(image));
encoder.Save(fileStream);
}
}
By the way, note that there's a bug in Clipboard.GetImage. It shouldn't be a problem if you just save the image to a file, but it will be if you want to display it.
EDIT : the bug mentioned above seems to be fixed in 4.0
This clears up the BitmapFrame.Create issue that you have.
public static void SaveClipboardImageToFile(string filePath)
{
//var image = Clipboard.GetImage();
BitmapSource image = (BitmapSource)Clipboard.GetImage();
using (var fileStream = new FileStream(filePath, FileMode.Create))
{
BitmapEncoder encoder = new PngBitmapEncoder();
//encoder.Frames.Add(BitmapFrame.Create(image));
encoder.Frames.Add(BitmapFrame.Create(image As BitmapSource));
encoder.Save(fileStream);
}
}