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Question

我一直在寻找如何提高波形图的渲染性能。目前我正在使用（尽可能多地）优化的基于 GDI 的渲染例程：

Private Sub Calculate2(ByVal aData()() As Double)
    'aData size: 1000 traces with 200k points each -> Dim aData(1000, 200000)

    'Some data preparations doing roughly the same as they would in the real app
    Dim PS_Y As Double = 1
    Dim Origin As PointF = New PointF(Rnd() * 100, Rnd() * 100)
    PS_Y = Rnd() + 0.1
    Dim Data(), ST As Double
    Dim lPoints As New List(Of PointF)
    Dim PS_X As Double = Rnd() + 0.1

    'Graphics initialisation
    Dim Img As New Bitmap(900, 600)
    Dim ImgGR As Graphics = Graphics.FromImage(Img)
    ImgGR.Clear(Color.White)
    Dim WFPen As New Pen(Brushes.Black, 1)

    'Cache property values for faster access:
    Dim l As Integer = 100 'ChartRect.Left
    Dim r As Integer = 1000 'ChartRect.Right

    'Process trace by trace:
    For i = 0 To aData.Length - 1
        ST = Rnd() 'x distance of the points
        Data = aData(i) 'y values, 1 per x value

        If Data.Length = 0 Then Continue For

        'scale precalculations, first & last displayed points:
        Dim ScaleX As Double = ST * PS_X
        Dim OrigX As Single = Origin.X

        Dim iStart As Integer = (l - OrigX) / ScaleX
        Dim iEnd As Integer = (r - OrigX) / ScaleX
        If iStart < 0 Then iStart = 0
        If iEnd < 0 Then iEnd = 0
        If iEnd > Data.Length - 1 Then iEnd = Data.Length - 1
        If iStart > Data.Length - 1 Then iStart = Data.Length - 1

        'Make sure that for benchmarking purposes all points are displayed, next 2 lines do not exist in real code:
        iStart = 0
        iEnd = Data.Length - 1

        If iEnd < iStart Then Continue For

        'point calculations using the pecalculated values:
        Dim APT(iEnd - iStart) As PointF
        For j = iStart To iEnd
            APT(j - iStart) = Origin + New SizeF(j * ScaleX, -(Data(j) * PS_Y))
        Next



        ImgGR.DrawLines(WFPen, APT)
        'Commenting out this line reduces the time needed for executing this whole routine from 42.4s to 4.76s
        'Hence most of the time spent even with all the scaling is still in rendering the spline.
    Next

我尝试过使用 Direct2D 的方法，但它甚至比 GDI 中的“DrawLines”方法慢得多：

 'Imports D2D = Microsoft.WindowsAPICodePack.DirectX.Direct2D1
'Imports DX = Microsoft.WindowsAPICodePack.DirectX
Dim TGT As D2D.RenderTarget
Private Sub initd2d()
    Dim fac As D2D.D2DFactory = D2D.D2DFactory.CreateFactory(Microsoft.WindowsAPICodePack.DirectX.Direct2D1.D2DFactoryType.SingleThreaded)

    Dim imgf As DX.WindowsImagingComponent.ImagingFactory
    imgf = DX.WindowsImagingComponent.ImagingFactory.Create

    'Dim pf As New D2D.PixelFormat(DX.Graphics.Format.B8G8R8A8UNorm, D2D.AlphaMode.Ignore)
    Dim pf As New D2D.PixelFormat(DX.Graphics.Format.Unknown, D2D.AlphaMode.Unknown)

    Dim bmp As DX.WindowsImagingComponent.ImagingBitmap
    bmp = imgf.CreateImagingBitmap(CUInt(900), CUInt(600), DX.WindowsImagingComponent.PixelFormats.Pbgra32Bpp, DX.WindowsImagingComponent.BitmapCreateCacheOption.CacheOnLoad)

    Dim rtp As New D2D.RenderTargetProperties(D2D.RenderTargetType.Default, pf, 0, 0, D2D.RenderTargetUsages.None, Microsoft.WindowsAPICodePack.DirectX.Direct3D.FeatureLevel.Default)
    TGT = fac.CreateWicBitmapRenderTarget(bmp, rtp)


    TGT.Clear(New D2D.ColorF(Color.White.ToArgb))
End Sub

'104,7s execution time:
Private Sub drawd2d()
    Dim p1 As New D2D.Point2F(1, 10.5)
    Dim p2 As New D2D.Point2F(1.01, 10)
    Dim b As D2D.Brush = TGT.CreateSolidColorBrush(New D2D.ColorF(0, 0, 255))
    TGT.BeginDraw()

    For i = 0 To 200000 * 1000
        TGT.DrawLine(p1, p2, b, 1)
    Next
End Sub

数据维度在这个应用程序中是常用的，所以请不要问我为什么需要它。

我也知道它必须以某种方式更快地显示它，因为首先生成数据的应用程序设法在大约 3 秒内渲染 4 条具有 50M 点的轨迹，这与数据量大致相同。

如果有人以前做过类似的事情，如果你能指出我正确的方向，我将非常感激，或者如果可以的话，给我一个替代方法，我可以如何将 PointF-Array 或类似结构渲染为位图。

编辑：请记住，这些是基准程序，旨在执行与原始软件相同的计算，而无需加载程序的其余部分。Data()() 数组是由软件动态生成的，因此必须检查维度并对其采取行动。

清理功能以及与问题无关的数据加载和图片显示功能、网格和其他代码已被删除。

EDIT2：包括数据生成例程的代码示例：

    Sub Main()
    Dim T As New HiResTimer
    Dim StartTime, StopTime As Long

    'initd2d()

    PrepareData(10, 200000)



    StartTime = T.Value
    For i = 1 To 1
        'drawd2d()
        Calculate2(100, 0, 200000)
    Next
    StopTime = T.Value

    Dim Elapsed As Double = (StopTime - StartTime) / T.Frequency
    Debug.Print("Time: " & Elapsed)

End Sub

Dim aData()() As Double
Private Sub PrepareData(ByVal WaveformCount As Integer, ByVal Length As Integer)
    Dim Offset As Double = 0
    Dim Amplitude As Double = 100

    Dim SineCount As Double = 4
    Dim SineBase As Double = 2 * Math.PI / Length * SineCount

    ReDim aData(WaveformCount - 1)
    For i = 0 To WaveformCount - 1
        ReDim aData(i)(Length - 1)

        For j = 0 To Length - 1
            aData(i)(j) = Amplitude * Math.Sin(SineBase * j) + Offset + Rnd() * Amplitude * 0.05
        Next
    Next
End Sub

Private Sub Calculate2(ByVal AmplitudeUsed As Double, ByVal OffsetUsed As Double, ByVal LengthUsed As Integer)
    Dim PS_Y As Double

    'Instead of making this random, here a real calculation for the scale (chartheight / biggest waveform amplitude) :
    PS_Y = 600 / (AmplitudeUsed * 2 + AmplitudeUsed * 0.1)  ' Rnd() + 0.1

    'Since our calculation method oscillates around zero with the same amplitude we can predict that we need the following offset:
    Dim Origin As PointF = New PointF(0, 300)


    Dim Data(), ST As Double
    Dim lPoints As New List(Of PointF)

    'set the x axis scale to make our waveform fit exactly:
    Dim PS_X As Double = 900 / LengthUsed

    Dim Img As New Bitmap(900, 600)
    Dim ImgGR As Graphics = Graphics.FromImage(Img)
    ImgGR.Clear(Color.White)
    Dim WFPen As New Pen(Brushes.Black, 1)

    'theese 2 values simply define an area in the picture where the waveforms are actually visible to not overlap with the axis / legend, set it to something that makes sense
    Dim l As Integer = 20 'ChartRect.Left
    Dim r As Integer = 700 'ChartRect.Right

    For i = 0 To aData.Length - 1
        'Set sampletime to 1 second to keep the predefined scale from above, but still do the calculation as it would be needed with real data:
        ST = 1 ' Rnd()
        Data = aData(i)

        If Data.Length = 0 Then Continue For

        Dim ScaleX As Double = ST * PS_X
        Dim OrigX As Single = Origin.X

        Dim iStart As Integer = (l - OrigX) / ScaleX
        Dim iEnd As Integer = (r - OrigX) / ScaleX
        If iStart < 0 Then iStart = 0
        If iEnd < 0 Then iEnd = 0
        If iEnd > Data.Length - 1 Then iEnd = Data.Length - 1
        If iStart > Data.Length - 1 Then iStart = Data.Length - 1

        iStart = 0
        iEnd = Data.Length - 1

        If iEnd < iStart Then Continue For

        Dim APT(iEnd - iStart) As PointF
        For j = iStart To iEnd
            APT(j - iStart) = Origin + New SizeF(j * ScaleX, -(Data(j) * PS_Y))
        Next



        ImgGR.DrawLines(WFPen, APT)

    Next


    PictureBox1.Image = Img
End Sub

Answer 1

您可以通过检查点之间的距离来加快速度，并跳过与前一个点太近的点。

您可以在距离计算中跳过 sqrt，并在需要时进行其他优化。

要查看这是否有益，请尝试使用 n/2 点运行基准测试。

Answer 2

这里是自动优化图形的代码块，它对许多小波形没有帮助，但它对 10k 和更大的波形有奇效：

Private Function Calculate3(ByVal aData()() As Double, ByVal AmplitudeUsed As Double, ByVal OffsetUsed As Double, ByVal LengthUsed As Integer) As Bitmap
    Dim PS_Y As Double

    'Instead of making this random, here a real calculation for the scale (chartheight / biggest waveform amplitude) :
    PS_Y = 600 / (AmplitudeUsed * 2 + AmplitudeUsed * 0.1)  ' Rnd() + 0.1

    'Since our calculation method oscillates around zero with the same amplitude we can predict that we need the following offset:
    Dim Origin As PointF = New PointF(0, 300)


    Dim Data(), ST As Double
    Dim lPoints As New List(Of PointF)

    'set the x axis scale to make our waveform fit exactly:
    Dim PS_X As Double = 900 / LengthUsed

    Dim Img As New Bitmap(900, 600)
    Dim ImgGR As Graphics = Graphics.FromImage(Img)
    ImgGR.Clear(Color.White)
    Dim WFPen As New Pen(Brushes.Black, 1)

    'theese 2 values simply define an area in the picture where the waveforms are actually visible to not overlap with the axis / legend, set it to something that makes sense
    Dim l As Integer = 20 'ChartRect.Left
    Dim r As Integer = 700 'ChartRect.Right

    Dim APT() As PointF
    For i = 0 To aData.Length - 1
        Dim iStart As Integer
        Dim iEnd As Integer

        Dim ScaleX As Double
        Dim OrigX As Single

        'Set sampletime to 1 second to keep the predefined scale from above, but still do the calculation as it would be needed with real data:
        ST = 1 ' Rnd()
        Data = aData(i)

        If Data.Length = 0 Then Continue For

        ScaleX = ST * PS_X
        OrigX = Origin.X

        iStart = (l - OrigX) / ScaleX
        iEnd = (r - OrigX) / ScaleX
        If iStart < 0 Then iStart = 0
        If iEnd < 0 Then iEnd = 0
        If iEnd > Data.Length - 1 Then iEnd = Data.Length - 1
        If iStart > Data.Length - 1 Then iStart = Data.Length - 1

        iStart = 0
        iEnd = Data.Length - 1

        If iEnd < iStart Then Continue For

        If ScaleX < 0.3 Then 'more than 3 lines per point, summarize
            Dim iPT As Integer

            Dim FirstX As Integer
            Dim LastX As Integer

            Dim MinY As Single
            Dim MaxY As Single
            Dim tVal As Single

            Dim iSt As Integer
            Dim iEn As Integer


            FirstX = Math.Truncate(iStart * ScaleX)
            LastX = Math.Ceiling(iEnd * ScaleX)

            ReDim APT((LastX - FirstX) * 2 - 1)
            For iX = FirstX To LastX - 1
                MinY = Single.MaxValue
                MaxY = Single.MinValue

                iSt = Math.Truncate(iX / ScaleX)
                iEn = Math.Truncate((iX + 1) / ScaleX) - 1
                If iSt < 0 Then iSt = 0
                If iEn > Data.Length - 1 Then iEn = Data.Length - 1

                For iDat = iSt To iEn
                    tVal = -Data(iDat) * PS_Y
                    If tVal > MaxY Then MaxY = tVal
                    If tVal < MinY Then MinY = tVal
                Next

                iPT = (iX - FirstX) * 2
                APT(iPT) = Origin + New SizeF(iX, MinY)
                APT(iPT + 1) = Origin + New SizeF(iX, MaxY)
            Next


        Else
            ReDim APT(iEnd - iStart)
            For j = iStart To iEnd
                APT(j - iStart) = Origin + New SizeF(j * ScaleX, -(Data(j) * PS_Y))
            Next

        End If




        ImgGR.DrawLines(WFPen, APT)
    Next


    Return Img
End Function

谢谢大家花时间阅读我的问题