在UserControl上使用画笔绘图 [英] Drawing with brush on UserControl

问题描述

我试图在UserControl控件上用画笔绘制。我可以绘制线条，圆圈和矩形。我不完全明白为什么我不能用画笔画画。下面的代码让我只指向MouseDown，然后它移动到MouseUp中设置的位置。在MouseMove中没有绘制内容。我想这里我不明白一些基本规则。

这段代码适用于行：

  public override void Draw（Graphics graphics）{
 graphics.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias; 
 graphics.DrawLine（new Pen（this.Color，this.PenSize），startPoint，endPoint）; 
} 
  

这段代码是我试图适应刷子的：

  public override void Draw（Graphics graphics）{
 if（this.bitmap！= null）{
 graphics = Graphics.FromImage （this.bitmap）; 
 graphics.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias; 
 graphics.DrawEllipse（new Pen（this.Color，this.PenSize），startPoint.X，startPoint.Y，
 this.PenSize，this.PenSize）; 
 graphics.DrawImage（this.bitmap，0，0）; 
 
 
 
 
 
 
 
此代码重新绘制对象列表：
  private void UserControl_Paint（object sender，PaintEventArgs e）{
 if（ObjectsList！= null）{
 ObjectsList.Draw （e.Graphics）; 
 
 
 
 
 $ b $ p 
 $ b 
由于代码提供了我想抓取位图图像点状线条画前后。我应该这样做吗？
解决方案
我不太了解您的问题，但在您的第二个代码中，他们似乎是一个失误。也许你应该试试这个： 
 
 
  public override void Draw（Graphics graphics）
 {
 if（ this.bitmap！= null）
 {
 Graphics g = Graphics.FromImage（this.bitmap）; 
 g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias; 
 g.DrawEllipse（new Pen（this.Color，this.PenSize），startPoint.X，startPoint.Y，this.PenSize，this.PenSize）; 
 graphics.DrawImage（this.bitmap，0，0）; 
 
 
 
 
 
 
 $ b 
否则，你在位图本身上绘制位图。希望这有助于。
 
I am trying to draw with brush on UserControl control. I can draw lines, circles and rectangles. I don't exactly understand why I cannot draw with brush. The code below gives me just point on MouseDown and then it moves to the position set in MouseUp. There is no content drawn during MouseMove. I suppose that I do not understand some basic rule here.

This code works for lines:
public override void Draw(Graphics graphics) {
  graphics.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;
  graphics.DrawLine(new Pen(this.Color, this.PenSize), startPoint, endPoint);
}
This code I am trygin to adapt for brush:
public override void Draw(Graphics graphics) {
  if (this.bitmap != null) {
    graphics = Graphics.FromImage(this.bitmap);
    graphics.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;
    graphics.DrawEllipse(new Pen(this.Color, this.PenSize), startPoint.X, startPoint.Y,
                         this.PenSize, this.PenSize);
    graphics.DrawImage(this.bitmap, 0, 0);
  }
}
This code repaints list of objects:
private void UserControl_Paint(object sender, PaintEventArgs e) {
  if (ObjectsList != null) {
    ObjectsList.Draw(e.Graphics);
  }
}
As the code presents I am trying to grab bitmap image before and after point-like line drawing. Should I do it other way?
解决方案
I don't really understand your question, but in your second code their seems to be a mistake. Maybe you should try this one:
public override void Draw(Graphics graphics)
{
    if (this.bitmap != null)
    {
        Graphics g = Graphics.FromImage(this.bitmap);
        g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;
        g.DrawEllipse(new Pen(this.Color, this.PenSize), startPoint.X, startPoint.Y, this.PenSize, this.PenSize);
        graphics.DrawImage(this.bitmap, 0, 0);
    }
}
Otherwise, you are drawing the bitmap on the bitmap itself. Hope this helps.

                        
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