Parasitemia/Parasitemia/GUI/GUI.fs

   1 module Parasitemia.GUI.Main
   2
   3 open System
   4 open System.IO
   5 open System.Linq
   6 open System.Windows
   7 open System.Windows.Media
   8 open System.Windows.Markup
   9 open System.Windows.Shapes
  10 open System.Windows.Controls
  11 open System.Diagnostics
  12 open Microsoft.Win32 // For the common dialogs.
  13
  14 open Emgu.CV.WPF
  15
  16 open Config
  17 open Types
  18
  19 let run (defaultConfig: Config) =
  20     let app = new Application()
  21     let mainWindow = Views.MainWindow()
  22     let ctrl (name: string): 'a =
  23         mainWindow.Root.FindName(name) :?> 'a
  24
  25     let colorRBCHealthy = Brushes.YellowGreen
  26     let colorRBCInfected = Brushes.Red
  27
  28     let state = State.State()
  29     let mutable currentScale = 1.
  30     let mutable displayHealthy = false
  31
  32     let menuExit: MenuItem = ctrl "menuExit"
  33     let menuSaveFile: MenuItem = ctrl "menuSave"
  34     let menuLoadFile: MenuItem = ctrl "menuOpen"
  35     let menuNewFile: MenuItem = ctrl "menuNew"
  36     let menuAddSourceImage: MenuItem = ctrl "menuAddSourceImage"
  37     let menuStartAnalysis: MenuItem = ctrl "menuStartAnalysis"
  38     let menuHightlightRBC: MenuItem = ctrl "menuHightlightRBC"
  39
  40     let txtPatient: TextBox = ctrl "txtPatient"
  41     let txtGlobalParasitemia: TextBox = ctrl "txtGlobalParasitemia"
  42
  43     let stackPreviews: StackPanel = ctrl "stackPreviews"
  44
  45     let scrollViewCurrentImage: ScrollViewer = ctrl "scrollViewCurrentImage"
  46     let borderCurrentImage: Border = ctrl "borderCurrentImage"
  47     let canvasCurrentImage: Canvas = ctrl "canvasCurrentImage"
  48     let txtImageInformation: TextBlock = ctrl "txtImageInformation"
  49
  50     let scrollRBC: ScrollViewer = ctrl "scrollRBC"
  51     let stackRBC: StackPanel = ctrl "stackRBC"
  52
  53     // Initializations.
  54     menuHightlightRBC.IsChecked <- displayHealthy
  55
  56     // Utils.
  57     let extractRBCPreview (img: Emgu.CV.Image<Emgu.CV.Structure.Bgr, byte>) (rbc: RBC) : Emgu.CV.Image<Emgu.CV.Structure.Bgr, byte> =
  58         let rbcWidth = rbc.size.Width
  59         let rbcHeight = rbc.size.Height
  60         let x = rbc.center.X - rbcWidth / 2. |> Utils.roundInt
  61         let y = rbc.center.Y - rbcHeight / 2. |> Utils.roundInt
  62         let w = Utils.roundInt rbcWidth
  63         let h = Utils.roundInt rbcHeight
  64         //Utils.dprintfn "w: %A, h: %A, cx: %A, cy: %A, img.w: %A, img.h: %A" w h x y img.Width img.Height
  65         img.GetSubRect(System.Drawing.Rectangle(System.Drawing.Point((if x < 0 then 0 else x), (if y < 0 then 0 else y)),
  66                                                 System.Drawing.Size((if x + w >= img.Width then img.Width - x else w),
  67                                                                     (if y + h >= img.Height then img.Height - y else h))))
  68
  69     let setRBCFrameStyle (rbc: RBC) (frame: Views.RBCFrame) =
  70         frame.Opacity <- if displayHealthy || rbc.setManually || rbc.infected then 1. else 0.
  71         let color = if rbc.infected then colorRBCInfected else colorRBCHealthy
  72         frame.manuallyAdded.Visibility <- if rbc.setManually then Visibility.Visible else Visibility.Hidden
  73         frame.manuallyAdded.Fill <- color
  74         frame.border.Stroke <- color
  75
  76     let RBCFrameFromExisting (rbc: RBC) (frame: Views.RBCFrame) : Views.RBCFrame =
  77         frame.Visibility <- Visibility.Visible
  78         frame.Height <- rbc.size.Height
  79         frame.Width <- rbc.size.Width
  80         frame.Tag <- rbc
  81         setRBCFrameStyle rbc frame
  82         frame.border.StrokeThickness <- 1.
  83         frame.txtRBCNumber.Text <- rbc.num.ToString()
  84         frame
  85
  86     let highlightRBCFrame (frame: Views.RBCFrame) (highlight: bool) =
  87         let rbc = frame.Tag :?> RBC
  88         if highlight
  89         then
  90             frame.border.StrokeThickness <- 3.
  91             if not rbc.infected && not rbc.setManually && not displayHealthy then frame.Opacity <- 1.
  92         else
  93             frame.border.StrokeThickness <- 1.
  94             if not rbc.infected && not rbc.setManually && not displayHealthy then frame.Opacity <- 0.
  95
  96     let zoomToRBC (rbc: RBC) =
  97         scrollViewCurrentImage.ScrollToHorizontalOffset(rbc.center.X * currentScale - scrollViewCurrentImage.ViewportWidth / 2. + borderCurrentImage.BorderThickness.Left)
  98         scrollViewCurrentImage.ScrollToVerticalOffset(rbc.center.Y * currentScale - scrollViewCurrentImage.ViewportHeight / 2. + borderCurrentImage.BorderThickness.Top)
  99
 100     let parasitemiaText (nbTotal: int, nbInfected: int) : string =
 101         if nbTotal = 0
 102         then
 103             ""
 104         else
 105             let percent = 100. * (float nbInfected) / (float nbTotal)
 106             sprintf "%.1f %% (%d / %d)" percent nbInfected nbTotal
 107
 108     let updateCurrentImageInformation () =
 109         match state.CurrentImage with
 110         | Some srcImg ->
 111             let parasitemiaStr = parasitemiaText (state.ImageParasitemia srcImg)
 112             txtImageInformation.Inlines.Clear()
 113             txtImageInformation.Inlines.Add(Documents.Run("Parasitemia: ", FontWeight = FontWeights.Bold))
 114             txtImageInformation.Inlines.Add(parasitemiaStr)
 115             txtImageInformation.Inlines.Add(Documents.LineBreak())
 116
 117             txtImageInformation.Inlines.Add(Documents.Run("Average erytrocyte diameter: ", FontWeight = FontWeights.Bold))
 118             txtImageInformation.Inlines.Add(Documents.Run(string (Utils.roundInt <| 2. * srcImg.rbcRadius)))
 119             txtImageInformation.Inlines.Add(Documents.Run(" px"))
 120             txtImageInformation.Inlines.Add(Documents.LineBreak())
 121
 122             txtImageInformation.Inlines.Add(Documents.Run("Last analysis: ", FontWeight = FontWeights.Bold))
 123             txtImageInformation.Inlines.Add(Documents.Run(if srcImg.dateLastAnalysis.Ticks = 0L then "<Never>" else srcImg.dateLastAnalysis.ToLocalTime().ToString()))
 124         | _ -> ()
 125
 126     let updateGlobalParasitemia () =
 127         txtGlobalParasitemia.Text <- parasitemiaText state.GlobalParasitemia
 128
 129     let updateViewportPreview () =
 130         for preview in stackPreviews.Children |> Seq.cast<Views.ImageSourcePreview> do
 131             let srcImg = preview.Tag :?> SourceImage
 132             if Some srcImg = state.CurrentImage then
 133                 preview.viewport.Visibility <- Visibility.Visible
 134
 135                 let canvasWidth = canvasCurrentImage.ActualWidth * currentScale
 136                 let canvasHeight = canvasCurrentImage.ActualHeight * currentScale
 137                 let previewWidth = (preview.ActualWidth - preview.BorderThickness.Left - preview.BorderThickness.Right)
 138                 let previewHeight = (preview.ActualHeight - preview.BorderThickness.Top - preview.BorderThickness.Bottom)
 139
 140                 let marginLeft = previewWidth * (scrollViewCurrentImage.HorizontalOffset - borderCurrentImage.BorderThickness.Left) / canvasWidth - 2.
 141                 let marginRight = previewWidth * (canvasWidth - (scrollViewCurrentImage.HorizontalOffset - borderCurrentImage.BorderThickness.Right) - scrollViewCurrentImage.ViewportWidth) / canvasWidth - 2.
 142                 let marginTop = previewHeight * (scrollViewCurrentImage.VerticalOffset - borderCurrentImage.BorderThickness.Top) / canvasHeight - 2.
 143                 let marginBottom = previewHeight * (canvasHeight - (scrollViewCurrentImage.VerticalOffset - borderCurrentImage.BorderThickness.Bottom) - scrollViewCurrentImage.ViewportHeight) / canvasHeight - 2.
 144
 145                 preview.viewport.Margin <-
 146                     Thickness(
 147                         marginLeft,
 148                         marginTop,
 149                         marginRight,
 150                         marginBottom)
 151             else
 152                 preview.viewport.Visibility <- Visibility.Hidden
 153
 154     let rec setAsInfected (rbc: RBC) (infected: bool) =
 155         state.SetAsInfected rbc infected
 156         canvasCurrentImage.Children
 157         |> Seq.cast<Views.RBCFrame>
 158         |> Seq.iter
 159             (fun frame ->
 160                 if (frame.Tag :?> RBC) = rbc
 161                 then
 162                     setRBCFrameStyle rbc frame)
 163         updateRBCFramesPreview ()
 164         updateCurrentImageInformation ()
 165         updateGlobalParasitemia ()
 166
 167     and RBCFrame (rbc: RBC) : Views.RBCFrame =
 168         let frame = RBCFrameFromExisting rbc (Views.RBCFrame())
 169         frame.SetValue(Panel.ZIndexProperty, Int32.MaxValue - rbc.num) // To be sure the
 170         frame.menuRBCSetAsHealthy.Click.AddHandler(fun obj args -> setAsInfected (frame.Tag :?> RBC) false)
 171         frame.menuRBCSetAsInfected.Click.AddHandler(fun obj args -> setAsInfected (frame.Tag :?> RBC) true)
 172         frame.ContextMenuOpening.AddHandler(
 173             fun obj args ->
 174                 if (frame.Tag :?> RBC).infected
 175                 then
 176                     frame.menuRBCSetAsHealthy.Visibility <- Visibility.Visible
 177                     frame.menuRBCSetAsInfected.Visibility <- Visibility.Collapsed
 178                 else
 179                     frame.menuRBCSetAsHealthy.Visibility <- Visibility.Collapsed
 180                     frame.menuRBCSetAsInfected.Visibility <- Visibility.Visible)
 181
 182         frame.ContextMenuClosing.AddHandler(fun obj args -> if not frame.IsMouseOver then highlightRBCFrame frame false )
 183         frame.MouseEnter.AddHandler(fun obj args -> highlightRBCFrame frame true)
 184         frame.MouseLeave.AddHandler(fun obj args -> if not frame.grid.ContextMenu.IsOpen then highlightRBCFrame frame false)
 185         frame
 186
 187     and updateRBCFramesPreview () =
 188         match state.CurrentImage with
 189         | Some srcImg ->
 190             let mutable currentPreview = 0
 191             for rbc in srcImg.rbcs |> List.filter (fun rbc -> displayHealthy || rbc.infected) do
 192                 let previewInfected =
 193                     if currentPreview < stackRBC.Children.Count
 194                     then
 195                         RBCFrameFromExisting rbc (stackRBC.Children.[currentPreview] :?> Views.RBCFrame)
 196                     else
 197                         let f = RBCFrame rbc
 198                         f.MouseLeftButtonUp.AddHandler(fun obj args -> zoomToRBC (f.Tag :?> RBC))
 199                         stackRBC.Children.Add(f) |> ignore
 200                         f
 201
 202                 currentPreview <- currentPreview + 1
 203
 204                 previewInfected.Height <- stackRBC.ActualHeight
 205                 previewInfected.Width <- stackRBC.ActualHeight * rbc.size.Width / rbc.size.Height
 206                 previewInfected.border.Fill <- ImageBrush(BitmapSourceConvert.ToBitmapSource(extractRBCPreview srcImg.img rbc))
 207
 208             stackRBC.Children.RemoveRange(currentPreview, stackRBC.Children.Count - currentPreview)
 209         | _ -> ()
 210
 211         updateViewportPreview ()
 212
 213     let updateRBCFramesCurrent () =
 214         match state.CurrentImage with
 215         | Some srcImg ->
 216             let mutable currentCanvas = 0
 217             for rbc in srcImg.rbcs do
 218                 let frame =
 219                     if currentCanvas < canvasCurrentImage.Children.Count
 220                     then
 221                         RBCFrameFromExisting rbc (canvasCurrentImage.Children.[currentCanvas] :?> Views.RBCFrame)
 222                     else
 223                         let f = RBCFrame rbc
 224                         f.Root.Opacity <- 0.7
 225                         canvasCurrentImage.Children.Add(f) |> ignore
 226                         f
 227
 228                 currentCanvas <- currentCanvas + 1
 229
 230                 Canvas.SetLeft(frame, rbc.center.X - rbc.size.Width / 2.)
 231                 Canvas.SetTop(frame, rbc.center.Y - rbc.size.Height / 2.)
 232
 233             for i in currentCanvas .. canvasCurrentImage.Children.Count - 1 do
 234                 canvasCurrentImage.Children.[i].Visibility <- Visibility.Hidden
 235         | _ -> ()
 236
 237     let saveCurrentDocument () =
 238         if state.FilePath = ""
 239         then
 240             let dialog = SaveFileDialog(AddExtension = true, DefaultExt = PiaZ.extension, Filter = PiaZ.filter);
 241             let res = dialog.ShowDialog()
 242             if res.HasValue && res.Value
 243             then
 244                 state.FilePath <- dialog.FileName
 245                 state.Save()
 246         else
 247             state.Save()
 248
 249     // Ask the use to save the current document if neccessary.
 250     let askSaveCurrent () =
 251         if state.AlteredSinceLastSave
 252         then
 253             match MessageBox.Show("Would you like to save the current document?", "Saving the current document", MessageBoxButton.YesNo, MessageBoxImage.Question) with
 254             | MessageBoxResult.Yes -> saveCurrentDocument ()
 255             | _ -> ()
 256
 257     let updateCurrentImage () =
 258         match state.CurrentImage with
 259         | Some srcImg ->
 260             // Highlight the preview.
 261             stackPreviews.Children
 262             |> Seq.cast<Views.ImageSourcePreview>
 263             |> Seq.iter (fun preview -> preview.border.BorderThickness <- Thickness(if preview.Tag = (srcImg :> Object) then 3. else 0.))
 264
 265             canvasCurrentImage.Height <- float srcImg.img.Height
 266             canvasCurrentImage.Width <- float srcImg.img.Width
 267             canvasCurrentImage.Background <- ImageBrush(BitmapSourceConvert.ToBitmapSource(srcImg.img))
 268
 269             updateRBCFramesCurrent ()
 270             updateRBCFramesPreview ()
 271             updateCurrentImageInformation ()
 272         | None ->
 273             stackRBC.Children.Clear()
 274             canvasCurrentImage.Children.Clear()
 275             canvasCurrentImage.Background <- Brushes.Black
 276
 277     let setCurrentImage (srcImg: SourceImage) =
 278         if state.CurrentImage.IsNone || state.CurrentImage.Value <> srcImg
 279         then
 280             state.CurrentImage <- Some srcImg
 281             updateCurrentImage ()
 282
 283     let addPreview (srcImg: SourceImage) =
 284         let imgCtrl = Views.ImageSourcePreview(Margin = Thickness(3.))
 285
 286         imgCtrl.menuRemoveImage.Click.AddHandler(fun obj args ->
 287             stackPreviews.Children.Remove(imgCtrl)
 288             let srcImg = imgCtrl.Tag :?> SourceImage
 289             let currentRemoved = Some srcImg = state.CurrentImage
 290             state.RemoveSourceImage srcImg
 291             if currentRemoved
 292             then
 293                 updateCurrentImage()
 294             stackPreviews.Children |> Seq.cast<Views.ImageSourcePreview> |> Seq.iter (fun imgPreview -> imgPreview.txtImageNumber.Text <- (imgPreview.Tag :?> SourceImage).num.ToString()))
 295
 296         imgCtrl.Tag <- srcImg
 297         imgCtrl.txtImageNumber.Text <- srcImg.num.ToString()
 298         let width = 200
 299         let height = srcImg.img.Height * width / srcImg.img.Width
 300         imgCtrl.imagePreview.Source <- BitmapSourceConvert.ToBitmapSource(srcImg.img.Resize(width, height, Emgu.CV.CvEnum.Inter.Cubic))
 301         stackPreviews.Children.Add(imgCtrl) |> ignore
 302
 303         // Zoom to a mouse position into the control 'imgCtrl'.
 304         let zoomTo (mousePos: Point) =
 305             let canvasW = canvasCurrentImage.ActualWidth * currentScale
 306             let canvasH = canvasCurrentImage.ActualHeight * currentScale
 307             let centerX = (mousePos.X - imgCtrl.BorderThickness.Left) / (imgCtrl.ActualWidth - imgCtrl.BorderThickness.Left) * canvasW
 308             let centerY = (mousePos.Y - imgCtrl.BorderThickness.Top) / (imgCtrl.ActualHeight - imgCtrl.BorderThickness.Top) * canvasH
 309             scrollViewCurrentImage.ScrollToHorizontalOffset(centerX - scrollViewCurrentImage.ViewportWidth / 2. + borderCurrentImage.BorderThickness.Left)
 310             scrollViewCurrentImage.ScrollToVerticalOffset(centerY - scrollViewCurrentImage.ViewportHeight / 2. + borderCurrentImage.BorderThickness.Top)
 311
 312         imgCtrl.MouseLeftButtonDown.AddHandler(fun obj args ->
 313             setCurrentImage (state.SourceImages |> Seq.find (fun srcImg -> (srcImg :> Object) = imgCtrl.Tag))
 314             imgCtrl.UpdateLayout()
 315             zoomTo (args.GetPosition(imgCtrl))
 316             imgCtrl.CaptureMouse() |> ignore)
 317
 318         imgCtrl.MouseMove.AddHandler(fun obj args ->
 319             if imgCtrl.IsMouseCaptured
 320             then
 321                 zoomTo (args.GetPosition(imgCtrl)))
 322
 323         imgCtrl.MouseLeftButtonUp.AddHandler(fun obj args ->
 324             if imgCtrl.IsMouseCaptured
 325             then
 326                 imgCtrl.ReleaseMouseCapture())
 327
 328
 329     let updatePreviews () =
 330         stackPreviews.Children.Clear ()
 331         for srcImg in state.SourceImages do
 332             addPreview srcImg
 333         updateCurrentImage ()
 334
 335     let updateGUI () =
 336         txtPatient.Text <- state.PatientID
 337         updatePreviews ()
 338         updateGlobalParasitemia ()
 339
 340     txtPatient.TextChanged.AddHandler(fun obj args -> state.PatientID <- txtPatient.Text)
 341
 342     menuExit.Click.AddHandler(fun obj args ->
 343         askSaveCurrent ()
 344         mainWindow.Root.Close())
 345
 346     menuSaveFile.Click.AddHandler(fun obj args -> saveCurrentDocument ())
 347
 348     menuLoadFile.Click.AddHandler(fun obj args ->
 349         // TODO: if current state not saved and not empty, ask to save it.
 350         let dialog = OpenFileDialog(Filter = PiaZ.filter)
 351         let res = dialog.ShowDialog()
 352         if res.HasValue && res.Value
 353         then
 354             askSaveCurrent ()
 355             state.FilePath <- dialog.FileName
 356             state.Load()
 357             updateGUI ())
 358
 359     menuNewFile.Click.AddHandler(fun obj args ->
 360         askSaveCurrent ()
 361         state.Reset()
 362         updateGUI())
 363
 364     menuAddSourceImage.Click.AddHandler(fun obj args ->
 365         let dialog = OpenFileDialog(Filter = "Image Files|*.png;*.jpg;*.tif;*.tiff")
 366         let res = dialog.ShowDialog()
 367         if res.HasValue && res.Value
 368         then
 369             let srcImg = state.AddSourceImage(dialog.FileName)
 370             addPreview srcImg
 371             updateGlobalParasitemia ()
 372             if state.SourceImages.Count() = 1
 373             then
 374                 updateCurrentImage ())
 375
 376     menuStartAnalysis.Click.AddHandler(fun obj args ->
 377         if Analysis.showWindow mainWindow.Root state defaultConfig
 378         then
 379             updateGlobalParasitemia ()
 380             updateCurrentImage ())
 381
 382     menuHightlightRBC.Click.AddHandler(fun obj args ->
 383         displayHealthy <- menuHightlightRBC.IsChecked
 384         updateRBCFramesPreview ()
 385         updateRBCFramesCurrent ())
 386
 387     // Zoom on the current image.
 388     let adjustCurrentImageBorders (deltaX: float) (deltaY: float) =
 389         borderCurrentImage.BorderThickness <-
 390             Thickness(
 391                 (scrollViewCurrentImage.ViewportWidth + deltaX) / 2.,
 392                 (scrollViewCurrentImage.ViewportHeight + deltaY) / 2.,
 393                 (scrollViewCurrentImage.ViewportWidth + deltaX) / 2.,
 394                 (scrollViewCurrentImage.ViewportHeight + deltaY) / 2.)
 395
 396     canvasCurrentImage.SizeChanged.AddHandler(fun obj args ->
 397         let deltaX = args.NewSize.Width - args.PreviousSize.Width
 398         let deltaY = args.NewSize.Height - args.PreviousSize.Height
 399         if deltaX > 0.5 || deltaY > 0.5
 400         then
 401             adjustCurrentImageBorders 0.0 0.0
 402             // Center the view at the center of the image initialy.
 403             scrollViewCurrentImage.UpdateLayout()
 404             scrollViewCurrentImage.ScrollToHorizontalOffset(borderCurrentImage.ActualWidth / 2. - scrollViewCurrentImage.ViewportWidth / 2.)
 405             scrollViewCurrentImage.ScrollToVerticalOffset(borderCurrentImage.ActualHeight / 2. - scrollViewCurrentImage.ViewportHeight / 2.))
 406
 407     scrollViewCurrentImage.SizeChanged.AddHandler(fun obj args ->
 408         let deltaX = args.NewSize.Width - args.PreviousSize.Width
 409         let deltaY = args.NewSize.Height - args.PreviousSize.Height
 410         adjustCurrentImageBorders deltaX deltaY
 411         scrollViewCurrentImage.ScrollToHorizontalOffset(scrollViewCurrentImage.HorizontalOffset + deltaX / 8.)
 412         scrollViewCurrentImage.ScrollToVerticalOffset(scrollViewCurrentImage.VerticalOffset + deltaY / 8.))
 413
 414     let mutable maxScale = 4.
 415     let mutable minScale = 0.25
 416     let currentImageScaleTransform = ScaleTransform()
 417     canvasCurrentImage.LayoutTransform <- currentImageScaleTransform
 418     borderCurrentImage.PreviewMouseWheel.AddHandler(fun obj args ->
 419         let scaleFactor = if args.Delta > 0 then 2.0 else 0.5
 420         if scaleFactor > 1. && currentScale < maxScale || scaleFactor < 1. && currentScale > minScale
 421         then
 422             let previousScale = currentScale
 423             currentScale <-
 424                 let newScale = currentScale * scaleFactor
 425                 if newScale > maxScale then maxScale elif newScale < minScale then minScale else newScale
 426             let realScaleFactor = currentScale / previousScale
 427
 428             let centerX = scrollViewCurrentImage.HorizontalOffset + scrollViewCurrentImage.ViewportWidth / 2. - borderCurrentImage.BorderThickness.Left
 429             let centerY = scrollViewCurrentImage.VerticalOffset + scrollViewCurrentImage.ViewportHeight / 2. - borderCurrentImage.BorderThickness.Top
 430
 431             currentImageScaleTransform.ScaleX <- currentScale
 432             currentImageScaleTransform.ScaleY <- currentScale
 433
 434             scrollViewCurrentImage.ScrollToHorizontalOffset(centerX * realScaleFactor - scrollViewCurrentImage.ViewportWidth / 2. + borderCurrentImage.BorderThickness.Left)
 435             scrollViewCurrentImage.ScrollToVerticalOffset(centerY * realScaleFactor - scrollViewCurrentImage.ViewportHeight / 2. + borderCurrentImage.BorderThickness.Top)
 436
 437         args.Handled <- true)
 438
 439     // Pan on the current image.
 440     let mutable scrollStartPosition = Point(0., 0.)
 441     let mutable scrollStartOffsetX = 0.
 442     let mutable scrollStartOffsetY = 0.
 443     borderCurrentImage.PreviewMouseLeftButtonDown.AddHandler(fun obj args ->
 444         scrollStartPosition <- args.GetPosition(scrollViewCurrentImage)
 445         scrollStartOffsetX <- scrollViewCurrentImage.HorizontalOffset
 446         scrollStartOffsetY <- scrollViewCurrentImage.VerticalOffset
 447         borderCurrentImage.Cursor <- Input.Cursors.ScrollAll
 448         borderCurrentImage.CaptureMouse() |> ignore
 449         args.Handled <- true)
 450
 451     borderCurrentImage.PreviewMouseMove.AddHandler(fun obj args ->
 452         if borderCurrentImage.IsMouseCaptured
 453         then
 454             let position = args.GetPosition(scrollViewCurrentImage)
 455             let deltaX = scrollStartPosition.X - position.X
 456             let deltaY = scrollStartPosition.Y - position.Y
 457             scrollViewCurrentImage.ScrollToHorizontalOffset(deltaX + scrollStartOffsetX)
 458             scrollViewCurrentImage.ScrollToVerticalOffset(deltaY + scrollStartOffsetY)
 459
 460             args.Handled <- true)
 461
 462     borderCurrentImage.PreviewMouseLeftButtonUp.AddHandler(fun obj args ->
 463         if borderCurrentImage.IsMouseCaptured
 464         then
 465             borderCurrentImage.Cursor <- Input.Cursors.Arrow
 466             borderCurrentImage.ReleaseMouseCapture()
 467             args.Handled <- true)
 468
 469     // Viewport preview.
 470     scrollViewCurrentImage.ScrollChanged.AddHandler(fun obj args -> updateViewportPreview ())
 471
 472     mainWindow.Root.Show()
 473     app.Run()