I am working on a program that downloads images from a URL to a bitmapimageand displays it. Next I try to save the bitmapimage to the harddrive using jpegbitmapencoder. The file is successfully created but the actual jpeg image is empty or 1 black pixel.
public Guid SavePhoto(string istrImagePath)
{
ImagePath = istrImagePath;
BitmapImage objImage = new BitmapImage(
new Uri(istrImagePath, UriKind.RelativeOrAbsolute));
PictureDisplayed.Source = objImage;
savedCreationObject = objImage;
Guid photoID = System.Guid.NewGuid();
string photolocation = photoID.ToString() + ".jpg"; //file name
JpegBitmapEncoder encoder = new JpegBitmapEncoder();
encoder.Frames.Add(BitmapFrame.Create(objImage));
using (FileStream filestream = new FileStream(photolocation, FileMode.Create))
{
encoder.Save(filestream);
}
return photoID;
}
This is the function that saves and displays the photo. The photo is displayed correctly but again when it is saved I get an empty jpeg or 1 black pixel.
When you create your BitmapImage from a Uri, time is required to download the image.
If you check the following property, the value will likely be TRUE
objImage.IsDownloading
As such, you much attach a listener to the DownloadCompleted event handler and move all processing to that EventHandler.
objImage.DownloadCompleted += objImage_DownloadCompleted;
Where that handler will look something like:
private void objImage_DownloadCompleted(object sender, EventArgs e)
{
JpegBitmapEncoder encoder = new JpegBitmapEncoder();
Guid photoID = System.Guid.NewGuid();
String photolocation = photoID.ToString() + ".jpg"; //file name
encoder.Frames.Add(BitmapFrame.Create((BitmapImage)sender));
using (var filestream = new FileStream(photolocation, FileMode.Create))
encoder.Save(filestream);
}
You will likely also want to add another EventHandler for DownloadFailed in order to gracefully handle any error cases.
Edit
Added full sample class based on Ben's comment:
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
SavePhoto("http://www.google.ca/intl/en_com/images/srpr/logo1w.png");
}
public void SavePhoto(string istrImagePath)
{
BitmapImage objImage = new BitmapImage(new Uri(istrImagePath, UriKind.RelativeOrAbsolute));
objImage.DownloadCompleted += objImage_DownloadCompleted;
}
private void objImage_DownloadCompleted(object sender, EventArgs e)
{
JpegBitmapEncoder encoder = new JpegBitmapEncoder();
Guid photoID = System.Guid.NewGuid();
String photolocation = photoID.ToString() + ".jpg"; //file name
encoder.Frames.Add(BitmapFrame.Create((BitmapImage)sender));
using (var filestream = new FileStream(photolocation, FileMode.Create))
encoder.Save(filestream);
}
}