Question

我遇到了一个关于GDI +效率的问题。有几个变量和方法如下： 1.Points，如A（代表一个坐标点，如X Y Z），B，C，D，E等。

2名为Cmd1的列表，用于按线程添加点

3.Paint方法，在此方法中，连接到线

的点集

4.Thread不断添加新的点，如F，G，H，I，J等。

在Paint Method中，我使用g.DrawLine（）链接a和b，c，d，e。在线程中，当我添加新点时，我将调用invalid来刷新组件。所以我的问题是，积分变得越来越多，我怎样才能保持高效率，并重新绘制，

不要从重点画线开始。

Sub DrawGLines2(g As Graphics)

    g.SmoothingMode = SmoothingMode.HighSpeed
    Dim Pen As New Pen(Brushes.White)
    Dim i As Int32
    'Dim c As Int32
    Dim preCmd1 As Cmd1
    Try
        For Each cmd As Cmd1 In Cmd1s            
                Dim pfs() As PointF = cmd.PointFs.ToArray
                If preCmd1 IsNot Nothing Then
                    g.DrawLine(Pen, cmd.PointFs(0), preCmd1.PointFs(0))
                End If
                preCmd1 = cmd
            End If

        Next
    Catch ex As Exception
        Debug.Print(ex.Message)
    End Try
End Sub

Private Sub Sheet_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles Me.Paint
    If Me.Cmd1s.Count>0 Then
        DrawGLines2(e.Graphics) 
    End If
End Sub

Public Sub AddPoint(x As Double, y As Double, z As Double, Optional G As Int32 = -1)
    Dim cmd1 As DrvSimu.Cmd1 = Nothing
    If cmd1 Is Nothing Then
        cmd1 = New DrvSimu.Cmd1
        Me.Cmd1s.Add(cmd1)
    End If

    Dim pf3d As New PointF3D(x, y, z)
    cmd1.PointF3Ds.Add(pf3d)

    Me.Invalidate()

End Sub

线程将调用AddPoint添加a，b，c，d，e点，并使用无效方法刷新，当我调用invalid时，＆＃34; For Each cmd As Cmd1 In Cmd1s＆＃34;对于每一个都将从A点开始，所以当点变得越来越多时，我怎样才能保持高效率，并且重绘，不要从A点开始重新绘制线条

Answer 1

这取决于你究竟想做什么。

一种可能性是您目前正在使用的那种。在每个无效时，您重绘所有行。根据绘图质量和cpu，您可以绘制更多或更少的行，但应该可以每毫秒绘制至少10行。

如果您只添加线条并且不需要删除或修改它们，您还可以将所有线条绘制到位图，并且无效时您只能将该图像绘制到屏幕上。通过这种方式，您只需要在添加图片时将新线条绘制到图片中。此方法的问题在于，如果要缩放或平移区域，或者如果要删除线条，则仍需要完全重绘。

作为起点，请参阅Graphics.FromImage（...）方法。使用Pixelformat Format32bppARGB获得最佳性能。

编辑：

public partial class LineForm : Form
{
    private Bitmap lineBitmap = null;

    private List<Tuple<PointF,PointF>> lines = new List<Tuple<PointF,PointF>>();

    private List<Tuple<PointF,PointF>> newLines = new List<Tuple<PointF,PointF>>();

    // must be set if you remove line, pan or zoom the view and if you resize the form.
    private bool redrawAll = false;

    public LineForm()
    {
        this.Paint += new System.Windows.Forms.PaintEventHandler(this.OnPaint);
        this.Resize += new System.EventHandler(this.OnResize);
    }

    private void OnResize(object sender, EventArgs e)
    {
        if (this.lineBitmap!= null)
        {
            this.lineBitmap.Dispose();
        }

        if (this.Width <= 0 || this.Height <= 0)
        {
            return;
        }

        this.lineBitmap = new Bitmap(this.Width, this.Height, PixelFormat.Format32bppPArgb);
        this.redrawAll = true;
    }

    private void OnPaint(object sender, PaintEventArgs e)
    {
        Graphics lineGfx = Graphics.FromImage(this.lineBitmap);
        // Settings for best drawing Performance. Must be adjusted for better quality
        lineGfx.CompositingQuality = CompositingQuality.HighSpeed;
        lineGfx.InterpolationMode = InterpolationMode.NearestNeighbor;
        lineGfx.SmoothingMode = SmoothingMode.None;
        lineGfx.PixelOffsetMode = PixelOffsetMode.None;
        lineGfx.TextRenderingHint = TextRenderingHint.AntiAliasGridFit;
        lineGfx.CompositingMode = CompositingMode.SourceCopy;

        // Only clear the Image and draw all lines if necessary
        if(this.redrawAll)
        {
            lineGfx.Clear(Color.Transparent);
            foreach(Tuple<PointF,PointF> line in this.lines)
            {
                lineGfx.DrawLine(Pens.Black, line.Item1, line.Item2);
            }
        }

        // Draw the new Lines to the Bitmap and store them to lines list
        foreach(Tuple<PointF,PointF> newline in this.newLines)
        {
            lineGfx.DrawLine(Pens.Black, newline.Item1, newline.Item2);
            tihs.lines.Add(newLine);
        }

        // Clear the newLines List as the liones are added to the lines List now.
        this.newLines.Clear();

        // Draw the Bitmap to the screen
        e.Graphics.DrawImageUnscaled(this.lineBitmap,0,0);
    }

    private void AddLine(PointF p1, PointF p2)
    {
        this.newLines.Add(new Tuple<PointF,PointF>(p1,p2));
        // Invalidate the view => OnPaint Event is raised;
        this.Invalidate();
    }
}

注意：我还没有为List操作添加任何锁定机制。为了防止在使用它们时更改列表，您应该添加一些锁。

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