WPF Blurry Images - Bitmap Class
- by Luke
I am using the following sample at http://blogs.msdn.com/dwayneneed/archive/2007/10/05/blurry-bitmaps.aspx within VB.NET. The code is shown below.
I am having a problem when my application loads the CPU is pegging 50-70%. I have determined that the problem is with the Bitmap class. The OnLayoutUpdated() method is calling the InvalidateVisual() continously. This is because some points are not returning as equal but rather, Point(0.0,-0.5)
Can anyone see any bugs within this code or know a better implmentation for pixel snapping a Bitmap image so it is not blurry?
p.s. The sample code was in C#, however I believe that it was converted correctly.
Imports System
Imports System.Collections.Generic
Imports System.Windows
Imports System.Windows.Media
Imports System.Windows.Media.Imaging
Class Bitmap Inherits FrameworkElement
' Use FrameworkElement instead of UIElement so Data Binding works as expected
Private _sourceDownloaded As EventHandler
Private _sourceFailed As EventHandler(Of ExceptionEventArgs)
Private _pixelOffset As Windows.Point
Public Sub New()
_sourceDownloaded = New EventHandler(AddressOf OnSourceDownloaded)
_sourceFailed = New EventHandler(Of ExceptionEventArgs)(AddressOf OnSourceFailed)
AddHandler LayoutUpdated, AddressOf OnLayoutUpdated
End Sub
Public Shared ReadOnly SourceProperty As DependencyProperty = DependencyProperty.Register("Source", GetType(BitmapSource), GetType(Bitmap), New FrameworkPropertyMetadata(Nothing, FrameworkPropertyMetadataOptions.AffectsRender Or FrameworkPropertyMetadataOptions.AffectsMeasure, New PropertyChangedCallback(AddressOf Bitmap.OnSourceChanged)))
Public Property Source() As BitmapSource
Get
Return DirectCast(GetValue(SourceProperty), BitmapSource)
End Get
Set(ByVal value As BitmapSource)
SetValue(SourceProperty, value)
End Set
End Property
Public Shared Function FindParentWindow(ByVal child As DependencyObject) As Window
Dim parent As DependencyObject = VisualTreeHelper.GetParent(child)
'Check if this is the end of the tree
If parent Is Nothing Then
Return Nothing
End If
Dim parentWindow As Window = TryCast(parent, Window)
If parentWindow IsNot Nothing Then
Return parentWindow
Else
' Use recursion until it reaches a Window
Return FindParentWindow(parent)
End If
End Function
Public Event BitmapFailed As EventHandler(Of ExceptionEventArgs)
' Return our measure size to be the size needed to display the bitmap pixels.
'
' Use MeasureOverride instead of MeasureCore so Data Binding works as expected.
' Protected Overloads Overrides Function MeasureCore(ByVal availableSize As Size) As Size
Protected Overloads Overrides Function MeasureOverride(ByVal availableSize As Size) As Size
Dim measureSize As New Size()
Dim bitmapSource As BitmapSource = Source
If bitmapSource IsNot Nothing Then
Dim ps As PresentationSource = PresentationSource.FromVisual(Me)
If Me.VisualParent IsNot Nothing Then
Dim window As Window = window.GetWindow(Me.VisualParent)
If window IsNot Nothing Then
ps = PresentationSource.FromVisual(window.GetWindow(Me.VisualParent))
ElseIf FindParentWindow(Me) IsNot Nothing Then
ps = PresentationSource.FromVisual(FindParentWindow(Me))
End If
End If
'
If ps IsNot Nothing Then
Dim fromDevice As Matrix = ps.CompositionTarget.TransformFromDevice
Dim pixelSize As New Vector(bitmapSource.PixelWidth, bitmapSource.PixelHeight)
Dim measureSizeV As Vector = fromDevice.Transform(pixelSize)
measureSize = New Size(measureSizeV.X, measureSizeV.Y)
Else
measureSize = New Size(bitmapSource.PixelWidth, bitmapSource.PixelHeight)
End If
End If
Return measureSize
End Function
Protected Overloads Overrides Sub OnRender(ByVal dc As DrawingContext)
Dim bitmapSource As BitmapSource = Me.Source
If bitmapSource IsNot Nothing Then
_pixelOffset = GetPixelOffset()
' Render the bitmap offset by the needed amount to align to pixels.
dc.DrawImage(bitmapSource, New Rect(_pixelOffset, DesiredSize))
End If
End Sub
Private Shared Sub OnSourceChanged(ByVal d As DependencyObject, ByVal e As DependencyPropertyChangedEventArgs)
Dim bitmap As Bitmap = DirectCast(d, Bitmap)
Dim oldValue As BitmapSource = DirectCast(e.OldValue, BitmapSource)
Dim newValue As BitmapSource = DirectCast(e.NewValue, BitmapSource)
If ((oldValue IsNot Nothing) AndAlso (bitmap._sourceDownloaded IsNot Nothing)) AndAlso (Not oldValue.IsFrozen AndAlso (TypeOf oldValue Is BitmapSource)) Then
RemoveHandler DirectCast(oldValue, BitmapSource).DownloadCompleted, bitmap._sourceDownloaded
RemoveHandler DirectCast(oldValue, BitmapSource).DownloadFailed, bitmap._sourceFailed
' ((BitmapSource)newValue).DecodeFailed -= bitmap._sourceFailed; // 3.5
End If
If ((newValue IsNot Nothing) AndAlso (TypeOf newValue Is BitmapSource)) AndAlso Not newValue.IsFrozen Then
AddHandler DirectCast(newValue, BitmapSource).DownloadCompleted, bitmap._sourceDownloaded
AddHandler DirectCast(newValue, BitmapSource).DownloadFailed, bitmap._sourceFailed
' ((BitmapSource)newValue).DecodeFailed += bitmap._sourceFailed; // 3.5
End If
End Sub
Private Sub OnSourceDownloaded(ByVal sender As Object, ByVal e As EventArgs)
InvalidateMeasure()
InvalidateVisual()
End Sub
Private Sub OnSourceFailed(ByVal sender As Object, ByVal e As ExceptionEventArgs)
Source = Nothing
' setting a local value seems scetchy...
RaiseEvent BitmapFailed(Me, e)
End Sub
Private Sub OnLayoutUpdated(ByVal sender As Object, ByVal e As EventArgs)
' This event just means that layout happened somewhere. However, this is
' what we need since layout anywhere could affect our pixel positioning.
Dim pixelOffset As Windows.Point = GetPixelOffset()
If Not AreClose(pixelOffset, _pixelOffset) Then
InvalidateVisual()
End If
End Sub
' Gets the matrix that will convert a Windows.Point from "above" the
' coordinate space of a visual into the the coordinate space
' "below" the visual.
Private Function GetVisualTransform(ByVal v As Visual) As Matrix
If v IsNot Nothing Then
Dim m As Matrix = Matrix.Identity
Dim transform As Transform = VisualTreeHelper.GetTransform(v)
If transform IsNot Nothing Then
Dim cm As Matrix = transform.Value
m = Matrix.Multiply(m, cm)
End If
Dim offset As Vector = VisualTreeHelper.GetOffset(v)
m.Translate(offset.X, offset.Y)
Return m
End If
Return Matrix.Identity
End Function
Private Function TryApplyVisualTransform(ByVal Point As Windows.Point, ByVal v As Visual, ByVal inverse As Boolean, ByVal throwOnError As Boolean, ByRef success As Boolean) As Windows.Point
success = True
If v IsNot Nothing Then
Dim visualTransform As Matrix = GetVisualTransform(v)
If inverse Then
If Not throwOnError AndAlso Not visualTransform.HasInverse Then
success = False
Return New Windows.Point(0, 0)
End If
visualTransform.Invert()
End If
Point = visualTransform.Transform(Point)
End If
Return Point
End Function
Private Function ApplyVisualTransform(ByVal Point As Windows.Point, ByVal v As Visual, ByVal inverse As Boolean) As Windows.Point
Dim success As Boolean = True
Return TryApplyVisualTransform(Point, v, inverse, True, success)
End Function
Private Function GetPixelOffset() As Windows.Point
Dim pixelOffset As New Windows.Point()
Dim ps As PresentationSource = PresentationSource.FromVisual(Me)
If ps IsNot Nothing Then
Dim rootVisual As Visual = ps.RootVisual
' Transform (0,0) from this element up to pixels.
pixelOffset = Me.TransformToAncestor(rootVisual).Transform(pixelOffset)
pixelOffset = ApplyVisualTransform(pixelOffset, rootVisual, False)
pixelOffset = ps.CompositionTarget.TransformToDevice.Transform(pixelOffset)
' Round the origin to the nearest whole pixel.
pixelOffset.X = Math.Round(pixelOffset.X)
pixelOffset.Y = Math.Round(pixelOffset.Y)
' Transform the whole-pixel back to this element.
pixelOffset = ps.CompositionTarget.TransformFromDevice.Transform(pixelOffset)
pixelOffset = ApplyVisualTransform(pixelOffset, rootVisual, True)
pixelOffset = rootVisual.TransformToDescendant(Me).Transform(pixelOffset)
End If
Return pixelOffset
End Function
Private Function AreClose(ByVal Point1 As Windows.Point, ByVal Point2 As Windows.Point) As Boolean
Return AreClose(Point1.X, Point2.X) AndAlso AreClose(Point1.Y, Point2.Y)
End Function
Private Function AreClose(ByVal value1 As Double, ByVal value2 As Double) As Boolean
If value1 = value2 Then
Return True
End If
Dim delta As Double = value1 - value2
Return ((delta < 0.00000153) AndAlso (delta > -0.00000153))
End Function
End Class
