I have a PDF Export in my Application (migradoc). To avoid freezing the GUI i want to run this Export as seperate Thread.
The PDF has also Charts embedded in it. To make those Charts look like the ones i use in my application i create and render them in Code. (visifire)
My Thread is already STA, but i get an Exception when running the WPF render Commands:
The calling thread cannot access this object because a different thread owns it
My Code:
chart.Measure(new Size(311, 180));
chart.Arrange(new Rect(0, 0, 311, 180));
chart.UpdateLayout();
ExportToPng(new Uri("C:\\" + i + "c.png"), chart);
public void ExportToPng(Uri path, Chart surface)
{
if (path == null) return;
// Save current canvas transform
Transform transform = surface.LayoutTransform;
// reset current transform (in case it is scaled or rotated)
surface.LayoutTransform = null;
// Create a render bitmap and push the surface to it
var renderBitmap =
new RenderTargetBitmap(
(int) surface.Width,
(int) surface.Height,
96d,
96d,
PixelFormats.Pbgra32);
renderBitmap.Render(surface);
// Create a file stream for saving image
using (var outStream = new FileStream(path.LocalPath, FileMode.Create))
{
// Use png encoder for our data
var encoder = new PngBitmapEncoder();
// push the rendered bitmap to it
encoder.Frames.Add(BitmapFrame.Create(renderBitmap));
// save the data to the stream
encoder.Save(outStream);
}
// Restore previously saved layout
surface.LayoutTransform = transform;
}
I already tried to dispatch this Commands, but i still keep getting the same Error.
DispatcherHelper.UIDispatcher.BeginInvoke((Action)(() =>
{
chart.Measure(new Size(311, 180));
chart.Arrange(new Rect(0, 0, 311, 180));
chart.UpdateLayout();
ExportToPng(new Uri("C:\\" + i + "c.png"), chart);
}));
you need to pass copy of any object which is the part of GUI thread as the GUI thread own them and that's why they can't be access in other thread. like you chart object you need to create a copy of chart object and then pass it into the thread so the owner of the object is your new thread.
If you need to render these on the same GUI thread then only chance is to render these on the same thread and wait to operation to complete.
Related
Context
I have a Basler camera that throw an event when a new image is captured.
In the event arg, I can get the image grabbed as a byte array.
I have to do computation on this image and then show it in a WPF application. The camera refresh rate is up to 40FPS.
Issue and found solution
A solution to convert a byte array to a WPF image can be found here : Convert byte array to image in wpf
This solution is great to convert only one time the byte array, however I feel like there is a lot of memory loss to do it at 40FPS. A new BitmapImage() is created every time and can't be disposed.
Would there be a better solution to display in WPF a byte array that changes up to 40 FPS ? (the way the problem is handled can be completely rethought)
Code
This solution to show the camera stream in WPF works, but the BitmapImage image = new BitmapImage(); line doesn't look good to me.
private void OnImageGrabbed(object sender, ImageGrabbedEventArgs e)
{
// Get the result
IGrabResult grabResult = e.GrabResult;
if (!grabResult.GrabSucceeded)
{
throw new Exception($"Grab error: {grabResult.ErrorCode} {grabResult.ErrorDescription}");
}
// Make process on the image
imageProcessor.Process(grabResult);
// Convert grabResult in BGR 8bit format
using Bitmap bitmap = new Bitmap(grabResult.Width, grabResult.Height, PixelFormat.Format32bppRgb);
BitmapData bmpData = bitmap.LockBits(new Rectangle(0, 0, bitmap.Width, bitmap.Height), ImageLockMode.ReadWrite, bitmap.PixelFormat);
IntPtr ptrBmp = bmpData.Scan0;
converter.Convert(ptrBmp, bmpData.Stride * bitmap.Height, grabResult);
bitmap.UnlockBits(bmpData);
// Creat the BitmapImage
BitmapImage image = new BitmapImage(); // <-- never Disposed !
using (MemoryStream memory = new MemoryStream())
{
bitmap.Save(memory, ImageFormat.Bmp);
memory.Position = 0;
image.BeginInit();
image.StreamSource = memory;
image.CacheOption = BitmapCacheOption.OnLoad;
image.EndInit();
image.Freeze();
}
LastFrame = image; // View is binded to LastFrame
}
I would suggest that you use a WriteableBitmap to display the result. This avoids the need to reallocate the UI image. If the pixel format in your source matches the one in the bitmap you can simply use WritePixels to update the image.
Note that you can only modify WriteableBitmap from the main thread, and the ImageGrabbed event will be raised on a background thread. And the grabResult will be disposed of once the event handler returns. So you will need to ask the UI thread to do the actual updating, and you will need a intermediate buffer for this. But this buffer can be pooled if needed.
An alternative might be to write your own loop, calling RetrieveResult repeatedly, this would let you dispose the grab results manually, after the UI has been updated. It might also be possible to keep a pool of WriteableBitmaps, I guess it should be safe to write to if it is not actually used by the UI.
On each frame, you are
creating a Bitmap
encoding it into a MemoryStream
creating a BitmapImage
decoding the MemoryStream into the BitmapImage
Better create a WritableBitmap once, and repeatedly call its WritePixels method.
You may still need to convert the raw buffer, since WPF does not seem to have an equivalent for PixelFormat.Format32bppRgb - or it is perhaps PixelFormats.Bgr32.
var wb = LastFrame as WriteableBitmap;
if (wb == null)
{
wb = new WriteableBitmap(
grabResult.Width, grabResult.Height,
96, 96, PixelFormats.Bgr32, null);
LastFrame = wb;
}
wb.WritePixels(...);
I am in a similar situation: Pulling live images off a camera and dumping them to the UI for "live" view. I spent a good deal of time trying to find the most efficient solution. For me, the turned out to be BitmapSource.Create. I take the raw array of bytes (plus a structure describing image characteristics like width, height, etc) and use one function call to convert it to a BitmapSource.
Now in my case, the images are greyscale, 8-bit images so if you're trying to show colors, your arguments would be different. But here's a snippet of what I do.
public class XimeaCameraImage : ICameraImage
{
public unsafe XimeaCameraImage(byte[] imageData, ImgParams imageParams)
{
Data = imageData;
var fmt = PixelFormats.Gray8;
var width = imageParams.GetWidth();
var bitsPerPixel = 8; // TODO: Get ready for other image formats
var height = imageParams.GetHeight();
var stride = (((bitsPerPixel * width) + 31) / 32) * 4;
var dpi = 96.0;
// Copy the raw, unmanaged, image data from the Sdk.Image object.
Source = BitmapSource.Create(
width,
height,
dpi,
dpi,
fmt,
BitmapPalettes.Gray256,
imageData,
stride);
Source.Freeze();
}
public byte[] Data { get; }
public BitmapSource Source { get; }
}
I'm trying to do the following:
Create a Livechart Cartesian chart in memory
Add the chart to a grid
Add Labels to the same grid
Add the grid to a Viewbox
Render the Viewbox as a PNG
Save the PNG to disk
The above should be run from a different thread in the background in order to allow UI reponsiveness.
However simple this may seem, I've been struggling to get a proper working solution. The following issues are relevant:
The Livechart (which is inside the Viewbox) takes time to render
Thus the chart needs to be given time to complete rendering before trying to save it as an image
I have found code which makes use of HwndSource, however it is not working all the time (works about 95% of the time). Without the HwndSource modification it NEVER works (always gets a chart with nothing on it)
Running the Run() function in a different UI thread does not work, as I get the following error message: WPF Dispatcher {“The calling thread cannot access this object because a different thread owns it.”}
So my questions are:
What is the right way to wait for the Livechart/Grid/ViewBox combination to finish rendering before saving it as an image? Maybe make use of the Loaded event? Note that I have tried to impelment it but cannot get it to work as I hit the 'threading' issue.
How can I run the entire process in a different UI thread?
See below for code
public void Run()
(
//Create Livechart which is a child of a Grid control
Grid gridChart = Charts.CreateChart();
//Creates a ViewBox control which has the grid as its child
Viewbox viewBox = WrapChart(gridChart,1400,700);
//Creates and saves the image
CreateAndSaveImage(viewBox ,path,name);
)
Below is the function which creates the Viewbox and add the grid as a child
public Viewbox viewBox WrapChart(Grid grid,int width,int height)
{
chart.grid.Width = width;
chart.grid.Height = height;
viewbox.Child = chart.grid;
viewbox.Width = width;
viewbox.Height = height;
viewbox.Measure(new System.Windows.Size(width, height));
viewbox.Arrange(new Rect(0, 0, width, height));
viewbox.UpdateLayout();
}
Function below creates and saves the image
public void CreateAndSaveImage(Viewbox viewbox,string folderPath,string fileName)
{
var x = HelperFunctions.GetImage(viewbox);
System.IO.FileStream stream = System.IO.File.Create(folderPath + fileName);
HelperFunctions.SaveAsPng(x, stream);
stream.Close();
}
The following code renders the viewbox to an image. Note that this is the only code that I could find which waits for the chart to finish loading. I have no idea how it works, but it works 95% of the time. Sometimes a chart still does not finish loading.
public static RenderTargetBitmap GetImage(Viewbox view)
{
using (new HwndSource(new HwndSourceParameters())
{
RootVisual =
(VisualTreeHelper.GetParent(view) == null
? view
: null)
})
{
Size size = new Size(view.ActualWidth, view.ActualHeight);
if (size.IsEmpty)
return null;
int actualWidth = Convert.ToInt32(size.Width);
int requiredWidth = Convert.ToInt32(size.Width * 1);
int actualHeight = Convert.ToInt32(size.Height);
int requiredHeight = Convert.ToInt32(size.Height * 1);
// Flush the dispatcher queue
view.Dispatcher.Invoke(DispatcherPriority.SystemIdle, new Action(() => { }));
var renderBitmap = new RenderTargetBitmap(requiredWidth, requiredHeight,
96d * requiredWidth / actualWidth, 96d * requiredHeight / actualHeight,
PixelFormats.Pbgra32);
DrawingVisual drawingvisual = new DrawingVisual();
using (DrawingContext context = drawingvisual.RenderOpen())
{
context.DrawRectangle(new VisualBrush(view), null, new Rect(new Point(), size));
context.Close();
}
renderBitmap.Render(view);
renderBitmap.Freeze();
return renderBitmap;
}
}
The following code saves the bitmap as a picture to file
public static void SaveAsPng(BitmapSource src, Stream outputStream)
{
PngBitmapEncoder encoder = new PngBitmapEncoder();
encoder.Frames.Add(BitmapFrame.Create(src));
encoder.Save(outputStream);
}
The following code is what I use to run the entire thing in a different thread. Note that it is not working, as I get the following error message:
WPF Dispatcher {“The calling thread cannot access this object because
a different thread owns it.”}.
Note that if I execute Run() normally (without any separate threads) it works, however sometimes the chart does not render properly (as explained previously).
Thread thread = new Thread(() =>
{
Run();
System.Windows.Threading.Dispatcher.Run();
});
thread.SetApartmentState(ApartmentState.STA);
thread.Start();
Try call this line for the chart:
this.chart.Model.Updater.Run(false, true);
This line updates the chart and always is visible when save to image.
I have written a small tool that creates screenshots of a number of STLs from different camera angles. vtkWindowToImageFilterconverts the contents of the vtkWin32OpenGLRenderWindowto an image, after which vtkPngWriteris used to write the image to a file.
I have noticed that the memory usage of the tool keeps rising with every screenshot it makes. After some debugging, I found out that the line of code that causes a rise in memory that is not freed at some point is
windowToImageFilter.Update();
Does anyone know if I should free some memory used by vtkWindowToImageFilter?
This is the complete function that creates the screenshots from different camera angles, for one set of STLs.
public void makeImage(vtkRenderWindow window, vtkRenderer renderer, string filePrefix="")
{
if (_parts.Count == 0)
return;
// Make cameras
Cameras cameras = new Cameras(_axial, _coronal, _sagittal, _parts[0].center, _parts[0].zoomfactor);
// VTK
// Setup vtkPNGwriter
vtkPNGWriter writer = vtkPNGWriter.New();
// Setup window to image filter
vtkWindowToImageFilter windowToImageFilter = vtkWindowToImageFilter.New();
windowToImageFilter.SetInput(window);
windowToImageFilter.SetMagnification(2); // set the resolution of the output image (3 times the current resolution of vtk render window)
foreach (string camName in cameraNames)
{
vtkCamera cam = cameras.getCameraByName(camName);
if (cam == null)
continue;
// Skip already created screenshots
if (File.Exists(getFilename(camName,filePrefix)))
continue;
// Clear renderer
renderer.RemoveAllViewProps();
// Show parts
this.show(renderer);
// Set camera
renderer.SetActiveCamera(cam);
renderer.GetActiveCamera().SetClippingRange(1.0, 1000);
window.Render();
// Update window to image filter
windowToImageFilter.Update();
// Write to png
writer.SetFileName(tempFile);
writer.SetInput(windowToImageFilter.GetOutput());
writer.Write();
// Crop png image
Bitmap img = new Bitmap(tempFile);
Bitmap imgCrop = cropImage(img);
imgCrop.MakeTransparent(Color.White);
imgCrop.Save(getFilename(camName,filePrefix));
// Dispose images (necessary to avoid memory filling)
img.Dispose();
imgCrop.Dispose();
// Delete temporary file
File.Delete(tempFile);
}
}
Because I noticed that the tool created several screenshots from the same camera viewpoint (caused by the SetInput method of vtkWindowToImageFilter being used outside the loop), I rewrote the code to create a vtkWindowToImageFilter and a vtkPngWriter inside the foreach loop. This allowed me to dispose them after they have been used, freeing up the memory.
Note that in the previous version of the code, I also tried to dispose the vtkWindowToImageFilter and vtkPngWriter right after the end of the loop, but this did not seem to free up any memory. Unfortunately, it is not clear to me why this would not work.
The current version of the code looks like this and does not cause a memory leak, as stated before.
public void makeImage(vtkRenderWindow window, vtkRenderer renderer,string filePrefix="")
{
if (_parts.Count == 0)
return;
// Make cameras
Cameras cameras = new Cameras(_axial, _coronal, _sagittal, _parts[0].center, _parts[0].zoomfactor);
foreach (string camName in cameraNames)
{
vtkCamera cam = cameras.getCameraByName(camName);
if (cam == null)
continue;
// Skip already created screenshots
if (File.Exists(getFilename(camName, filePrefix)))
continue;
// Clear renderer
renderer.RemoveAllViewProps();
// Show parts
this.show(renderer);
// Set camera
renderer.SetActiveCamera(cam);
renderer.GetActiveCamera().SetClippingRange(1.0, 1000);
window.Render();
// Update window to image filter
vtkWindowToImageFilter windowToImageFilter = vtkWindowToImageFilter.New();
windowToImageFilter.SetMagnification(4); // set the resolution of the output image (3 times the current resolution of vtk render window)
windowToImageFilter.SetInput(window);
// Write to png
vtkPNGWriter writer = vtkPNGWriter.New();
writer.SetInputConnection(windowToImageFilter.GetOutputPort());
writer.SetFileName(tempFile);
writer.Write();
// Dispose pipeline parts
windowToImageFilter.Dispose();
writer.Dispose();
// Crop png image
Bitmap img = new Bitmap(tempFile);
Bitmap imgCrop = cropImage(img, squareImages);
imgCrop.MakeTransparent(Color.White);
imgCrop.Save(getFilename(camName,filePrefix));
// Dispose images (necessary to avoid memory filling)
img.Dispose();
imgCrop.Dispose();
// Delete temporary file
File.Delete(tempFile);
}
}
I am having a problem with EmguCV. I used a demo application, and edited it to my needs.
It involves the following function:
public override Image<Gray, byte> DetectSkin(Image<Bgr, byte> Img, IColor min, IColor max)
{
Image<Hsv, Byte> currentHsvFrame = Img.Convert<Hsv, Byte>();
Image<Gray, byte> skin = new Image<Gray, byte>(Img.Width, Img.Height);
skin = currentHsvFrame.InRange((Hsv)min,(Hsv)max);
return skin;
}
In the demo application, the Image comes from a video. The frame is capured from the video like this:
Image<Bgr, Byte> currentFrame;
grabber = new Emgu.CV.Capture(#".\..\..\..\M2U00253.MPG");
grabber.QueryFrame();
currentFrame = grabber.QueryFrame();
In my application, the Image comes from a microsoft kinect stream.
I use the following function:
private void SensorColorFrameReady(object sender, ColorImageFrameReadyEventArgs e)
{
using (ColorImageFrame colorFrame = e.OpenColorImageFrame())
{
if (colorFrame != null)
{
// Copy the pixel data from the image to a temporary array
colorFrame.CopyPixelDataTo(this.colorPixels);
// Write the pixel data into our bitmap
this.colorBitmap.WritePixels(
new Int32Rect(0, 0, this.colorBitmap.PixelWidth, this.colorBitmap.PixelHeight),
this.colorPixels,
this.colorBitmap.PixelWidth * sizeof(int),
0);
Bitmap b = BitmapFromWriteableBitmap(this.colorBitmap);
currentFrame = new Image<Bgr, byte>(b);
currentFrameCopy = currentFrame.Copy();
skinDetector = new YCrCbSkinDetector();
Image<Gray, Byte> skin = skinDetector.DetectSkin(currentFrame, YCrCb_min, YCrCb_max);
}
}
}
private static System.Drawing.Bitmap BitmapFromWriteableBitmap(WriteableBitmap writeBmp)
{
System.Drawing.Bitmap bmp;
using (System.IO.MemoryStream outStream = new System.IO.MemoryStream())
{
BitmapEncoder enc = new BmpBitmapEncoder();
enc.Frames.Add(BitmapFrame.Create((BitmapSource)writeBmp));
enc.Save(outStream);
bmp = new System.Drawing.Bitmap(outStream);
}
return bmp;
}
Now, the demo application works, and mine doesn't. Mine gives the following exception:
And, the image here, contains the following:
I really don't understand this exception. And, now, when I run the demo, working aplication, the image, contains:
Which is, in my eyes, exactly the same. I really don't understand this. Help is very welcome!
To make things easier I've uploaded a working WPF solution for you to the code reference sourceforge page I've been building:
http://sourceforge.net/projects/emguexample/files/Capture/Kinect_SkinDetector_WPF.zip/download
https://sourceforge.net/projects/emguexample/files/Capture/
This was designed and tested using EMGU x64 2.42 so in the Lib folder of the project you will find the referenced dlls. If you are using a different version you will need to delete the current references and replace them with the version you're using.
Secondly the project is design like all projects from the code reference library to be built from the Emgu.CV.Example folder into the ..\EMGU 2.X.X.X\bin.. global bin directory where the opencv compiled libraries are within a folder either x86 or x64.
If you struggle to get the code working I can provide all components but I hate redistributing all the opencv files that you already have so let me know if you want this.
You will need to resize the Mainwindow manually to display both images as I didn't spend to much time playing with layout.
So the code...
In the form initialisation method I check for the kinect sensor and set up the eventhandlers for the frames ready. I have left the original threshold values and skinDetector type although I don't use the EMGU version I just forgot to remove it. You will need to play with the threshold values and so on.
//// Look through all sensors and start the first connected one.
//// This requires that a Kinect is connected at the time of app startup.
//// To make your app robust against plug/unplug,
//// it is recommended to use KinectSensorChooser provided in Microsoft.Kinect.Toolkit (See components in Toolkit Browser).
foreach (var potentialSensor in KinectSensor.KinectSensors)
{
if (potentialSensor.Status == KinectStatus.Connected)
{
this.KS = potentialSensor;
break;
}
}
//If we have a Kinect Sensor we will set it up
if (null != KS)
{
// Turn on the color stream to receive color frames
KS.ColorStream.Enable(ColorImageFormat.RgbResolution640x480Fps30);
//Turn on the depth stream to recieve depth frames
KS.DepthStream.Enable(DepthImageFormat.Resolution640x480Fps30);
//Start the Streaming process
KS.Start();
//Create a link to a callback to deal with the frames
KS.AllFramesReady += new EventHandler<AllFramesReadyEventArgs>(KS_AllFramesReady);
//We set up a thread to process the image/disparty map from the kinect
//Why? The kinect AllFramesReady has a timeout if it has not finished the streams will simply stop
KinectBuffer = new Thread(ProcessBuffer);
hsv_min = new Hsv(0, 45, 0);
hsv_max = new Hsv(20, 255, 255);
YCrCb_min = new Ycc(0, 131, 80);
YCrCb_max = new Ycc(255, 185, 135);
detector = new AdaptiveSkinDetector(1, AdaptiveSkinDetector.MorphingMethod.NONE);
skinDetector = new YCrCbSkinDetector();
}
I always play with the kinect data in a new thread for speed but you may want to advanced this to a Background worker if you plan to do any more heavy processing so it is better managed.
The thread calls the ProcessBuffer() method you can ignore all the commented code as this is the remanence of the code used to display the depth image. Again I'm using the Marshall copy method to keep things fast but the thing to look for is the Dispatcher.BeginInvoke in WPF that allows the images to be displayed from the Kinect thread. This is required as I'm not processing on the main thread.
//This takes the byte[] array from the kinect and makes a bitmap from the colour data for us
byte[] pixeldata = new byte[CF.PixelDataLength];
CF.CopyPixelDataTo(pixeldata);
System.Drawing.Bitmap bmap = new System.Drawing.Bitmap(CF.Width, CF.Height, System.Drawing.Imaging.PixelFormat.Format32bppRgb);
BitmapData bmapdata = bmap.LockBits(new System.Drawing.Rectangle(0, 0, CF.Width, CF.Height), ImageLockMode.WriteOnly, bmap.PixelFormat);
IntPtr ptr = bmapdata.Scan0;
Marshal.Copy(pixeldata, 0, ptr, CF.PixelDataLength);
bmap.UnlockBits(bmapdata);
//display our colour frame
currentFrame = new Image<Bgr, Byte>(bmap);
Image<Gray, Byte> skin2 = skinDetector.DetectSkin(currentFrame, YCrCb_min, YCrCb_max);
ExtractContourAndHull(skin2);
DrawAndComputeFingersNum();
//Display our images using WPF Dispatcher Invoke as this is a sub thread.
Dispatcher.BeginInvoke((Action)(() =>
{
ColorImage.Source = BitmapSourceConvert.ToBitmapSource(currentFrame);
}), System.Windows.Threading.DispatcherPriority.Render, null);
Dispatcher.BeginInvoke((Action)(() =>
{
SkinImage.Source = BitmapSourceConvert.ToBitmapSource(skin2);
}), System.Windows.Threading.DispatcherPriority.Render, null);
I hope this helps I will at some point neaten up the code I uploaded,
Cheers
I have a fair few images that I'm loading into a ListBox in my WPF application. Originally I was using GDI to resize the images (the originals take up far too much memory). That was fine, except they were taking about 400ms per image. Not so fine. So in search of another solution I found a method that uses TransformedBitmap (which inherits from BitmapSource). That's great, I thought, I can use that. Except I'm now getting memory leaks somewhere...
I'm loading the images asynchronously using a BackgroundWorker like so:
BitmapSource bs = ImageUtils.ResizeBitmapSource(ImageUtils.GetImageSource(photo.FullName));
//BitmapSource bs = ImageUtils.GetImageSource(photo.FullName);
bs.Freeze();
this.dispatcher.Invoke(new Action(() => { photo.Source = bs; }));
GetImageSource just gets the Bitmap from the path and then converts to BitmapSource.
Here's the code snippet for ResizeBitmapSource:
const int thumbnailSize = 200;
int width;
int height;
if (bs.Width > bs.Height)
{
width = thumbnailSize;
height = (int)(bs.Height * thumbnailSize / bs.Width);
}
else
{
height = thumbnailSize;
width = (int)(bs.Width * thumbnailSize / bs.Height);
}
BitmapSource tbBitmap = new TransformedBitmap(bs,
new ScaleTransform(width / bs.Width,
height / bs.Height, 0, 0));
return tbBitmap;
That code is essentially the code from:
http://rongchaua.net/blog/c-wpf-fast-image-resize/
Any ideas what could be causing the leak?
edit:
Here's the code for GetImageSource, as requested
using (var stream = new FileStream(path, FileMode.Open, FileAccess.Read))
{
using (var bmp = Image.FromStream(stream, false, false))
{
// Use WPF to resize
var bitmapSource = ConvertBitmapToBitmapSource(bmp);
bitmapSource = ResizeBitmapSource(bitmapSource);
return bitmapSource;
}
}
I think you misunderstood how the TransformedBitmap works. It holds onto a reference to the source bitmap, and transforms it in memory. Maybe you could encode the transformed bitmap into a memory stream, and read it right back out. I'm not sure how fast this would be, but you wouldn't then be holding on to the full sized bitmap.
I found this blog post that returned a WriteableBitmap with the TransformedBitmap as the source. The WriteableBitmap will copy the pixel data to a memory buffer in the initializer, so it doesn't actually hold on to a reference to the TransformedBitmap, or the full sized image.
At a guess, from looking at your code you might need to dispose of the bitmap returned by the call to ImageUtils.GetImageSource(photo.FullName).
I have also noted on the blog you pointed out that the author has added an update (11th of March) about inserting a using statement to prevent memory leaks.