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Question

我遇到了一个有关GDI 效率的问题。有几个变量和方法 如下：1.点，例如A（表示坐标点，例如X Y Z），B，C，D，E等。

2名为CMD1的列表，用于添加线程

的点

3. paint方法，在此方法中，连接到该行的点集

4.不断增加新点的线程，例如f，g，h，i，j等。

在油漆方法中，我使用g.drawline（）链接a和b，c，d，e。在线程中，当我添加新点时，我将无效刷新组件。所以我的问题是，要点越来越多，我如何保持高效率并重新绘制，

不要从A点开始到re drawline。

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

该线程将调用ADDPOINT添加A，B，C，D，E点，并使用无效的方法来刷新，当我调用Invalid时，每个CMD为CMD1中的CMD1在CMD1中的CMD1"将从一个点开始，因此，当要点变得越来越高时，我如何保持高效率，重新绘制，不要从一个点开始到drawline

Answer 1

这取决于您要做什么。

一种可能性是您当前正在使用的一种。在每个无效的情况下，您重新绘制了所有行。根据图形质量和CPU，您可以绘制或多或少的线条，但应该每毫秒至少绘制10行。

如果您仅添加行而无需删除或修改它们，则还可以将所有行绘制到位图，而在无效的情况下，您只将该图像绘制到屏幕上。通过此，您只需要在添加图片时将新线条绘制到图片中。此方法的问题是，如果要缩放或泛该区域，或者要删除行。

作为起点，请参见Graphics.fromimage（...）方法。使用PixelFormat格式32BPPARGB以最佳性能。

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：我没有在列表操作中添加任何锁定机制。为了防止使用列表时更改列表时，您应该添加一些锁。