Memory Leak in WPF Image Resizing - wpf

Question

I have following image resize and save code.
This code is executed in different thread in ASP.NET MVC Project. As
using (FileStream fs = new FileStream(file.File.FullName,
FileMode.Open, FileAccess.Read, FileShare.Read))
{
BitmapDecoder decoder = BitmapDecoder.Create(fs,
BitmapCreateOptions.PreservePixelFormat, BitmapCacheOption.None);
var img = decoder.Frames[0];
img.Freeze();
double width = Size;
double height = Size;
if (img.PixelWidth > img.PixelHeight)
{
height = (int)(((double)img.PixelHeight / (double)img.PixelWidth)
* (double)width);
}
else
{
width = (int)(((double)img.PixelWidth / (double)img.PixelHeight)
* (double)height);
}
var target = new TransformedBitmap(img,
new ScaleTransform(width / (double)img.PixelWidth, height
/ (double)img.PixelHeight, 0, 0));
RenderOptions.SetBitmapScalingMode(target, BitmapScalingMode.HighQuality);
var t = BitmapFrame.Create(target);
RenderOptions.SetBitmapScalingMode(t, BitmapScalingMode.HighQuality);
target.Freeze();
t.Freeze();
JpegBitmapEncoder enc = new JpegBitmapEncoder();
enc.Frames.Add(t);
enc.QualityLevel = 90;
using (FileStream fsout = saved.File.OpenWrite())
{
enc.Save(fsout);
}
}
I have used using around every IDisposable object, WPF objects do not implement IDisposable so I cant dispose them manually.
I read somewhere that calling Freeze will prevent memory leaks, but even after this, no improvement. Memory usage of this process keep on increasing.
What I need is, when an Image is uploaded, it has to be resized in 4 different resolutions, 150x150, 350x350, 700x700 and 1000x1000 , each of these resolutions are invoked parallely using Parallel.ForEach method.
My rest of website is just plain simple Database access using Entity Framework, which I doubt can cause any memory leak upto 3GB of memory usage.

Answer 1

I tried putting this in a loop in a stand-alone test program and followed the function with an explicit GC.Collect(). On .NET 4.5 at least, this shows that this code does not leak -- the memory stays steady after many many calls.
I think you'll need to look elsewhere in your code. You should try to profile it with Analyze > Launch Performance Wizard... and select .NET Memory Allocations and see what's using the memory.
For fun, I also tried .NET 3.5 and didn't experience a leak their either.