C# 如何在图像上画一条线？
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how to draw a line on a image?
提问by user1150071
i want to draw a line on a bmp image which is pass into a method using drawline method in C#
我想在 bmp 图像上绘制一条线，该线被传递到使用 C# 中的 drawline 方法的方法中
public void DrawLineInt(Bitmap bmp)
{
Pen blackPen = new Pen(Color.Black, 3);
int x1 = 100;
int y1 = 100;
int x2 = 500;
int y2 = 100;
// Draw line to screen.
e.Graphics.DrawLine(blackPen, x1, y1, x2, y2);
}
this give a error.So i want to know how to include paint event here (PaintEventArgs e )
这给出了一个错误。所以我想知道如何在这里包含绘画事件（PaintEventArgs e）
and also want to know how to pass parameters when we calling drawmethod? example
还想知道调用drawmethod时如何传递参数？例子
DrawLineInt(Bitmap bmp);
this give the following error "The name 'e' does not exist in the current context "
这给出了以下错误“当前上下文中不存在名称‘e’”
采纳答案by Tom
"Draw a line on a bmp image which is pass into a method using drawline method in C#"
“在 bmp 图像上绘制一条线，该线被传递到使用 C# 中的 drawline 方法的方法中”
PaintEventArgs e would suggest that you are doing this during the "paint" event for an object. Since you are calling this in a method, then no you do not need to add PaintEventArgs e anywhere.
PaintEventArgs e 会建议您在对象的“绘制”事件期间执行此操作。由于您是在方法中调用它，因此不需要在任何地方添加 PaintEventArgs e。
To do this in a method, use @BFree's answer.
要在方法中执行此操作，请使用@BFree 的答案。
public void DrawLineInt(Bitmap bmp)
{
Pen blackPen = new Pen(Color.Black, 3);
int x1 = 100;
int y1 = 100;
int x2 = 500;
int y2 = 100;
// Draw line to screen.
using(var graphics = Graphics.FromImage(bmp))
{
graphics.DrawLine(blackPen, x1, y1, x2, y2);
}
}
The "Paint" event is raised when the object is redrawn. For more information see:
重绘对象时会引发“Paint”事件。有关更多信息，请参阅：
http://msdn.microsoft.com/en-us/library/system.windows.forms.control.paint.aspx
http://msdn.microsoft.com/en-us/library/system.windows.forms.control.paint.aspx
回答by BFree
You need to get the Graphicsobject from the Imagelike so:
您需要Graphics从Image这样的对象中获取对象：
using(var graphics = Graphics.FromImage(bmp))
{
graphics.DrawLine(...)
}
