tiff viewer wpf application out of memory - wpf

Question

I'm working on a Tiff Viewer project which deals with big 24bit colored tif files (>70MB).
Here is the code how I load the tif file:
TiffBitmapDecoder tbd = new TiffBitmapDecoder(new Uri(_strTiffPath),BitmapCreateOptions.DelayCreation, BitmapCacheOption.Default);
_frames = tbd.Frames;
I use the default cache option to prevent loading the whole file in memory.
My application has a side thumbnails view (vertical StackPanel with Image), and a Page view which views the selected thumbnail.
I load only visible thumbnails by this code:
internal static BitmapSource GetThumbAt(int i)
{
try
{
if (i >= _frames.Count)
return null;
BitmapFrame bf = _frames[i];
bf.Freeze();
return bf;
}
catch (Exception ex)
{
return null;
}
}
My problem is when I scroll down the thumbnails view to load the new visible pages, the memory load increases and I run into out of memory !
I tried to unload invisible pages (that were already loaded) but that doesn't help !
img.Source = null
Thank you helping me to figure this out.

Answer 1

I figured it out !
As mentioned in my previous comment, this article helped me a lot.
I just adapted it to my code and the memory is now unloading correctly.
Here are the modifications I made to my code:
internal static BitmapSource GetThumbAt(int i)
{
try
{
if (i >= _frames.Count)
return null;
BitmapFrame bf = _frames[i];
BitmapSource bs = bf.Clone() as BitmapSource; //make a copy of the original because bf is frozen and can't take any new property
BitmapUtility.AddMemoryPressure(bs);
return bs;
}
catch (Exception ex)
{
return null;
}
}