how to get BitmapImage in codebehind from the image tag in xaml in wpf/silverlight

Question

i dont have a problem with binding a bitmapimage to image tag in codebehind for eg.

BitmapImage image = new BitmapImage();
imagetaginxaml.Source = image; // this         


        

Answer 1

How about using WriteableBitmap to make a copy of the image, and then using a MemoryStream to copy the original image into a copy?

// Create a WriteableBitmap from the Image control
WriteableBitmap bmp = new WriteableBitmap(imagetaginxaml, null);

// Load the contents of a MemoryStream from the WritableBitmap
MemoryStream m = new MemoryStream();
bmp.SaveJpeg(m, bmp.PixelWidth, bmp.PixelHeight, 0, 100);

// Read from the stream into a new BitmapImage object
m.Position = 0;
BitmapImage image = new BitmapImage();
image.SetSource(m);

// do something with the new BitmapImage object
// (for example, load another image control)
anotherimagetaginxaml.Source = image;

Answer 2

Well, Image.Source is of type ImageSource, there is no quarantee that it will be a BitmapImage, it may be though. If the source is created by the XAML parser it will be a BitmapFrameDecode (which is an internal class). Anyway, the only save assignment is:

ImageSource source = img.Source;

otherwise you need to cast:

BitmapImage source = (BitmapImage)img.Source;

which will throw an exception if the Source is not of this type. So you can either save-cast or try-catch:

//(Possibly check for img.Source != null first)
BitmapImage source = img.Source as BitmapImage;
if (source != null)
{
     //If img.Source is not null the cast worked.
}

try
{
    BitmapImage source = (BitmapImage)img.Source;
    //If this line is reached it worked.
}
catch (Exception)
{
    //Cast failed
}

You could also check the type beforehand using img.SourceisBitmapImage.