how to draw a line on a image?

Question

i want to draw a line on a bmp image which is pass into a method using drawline method in C#

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 )

and also want to know how to pass parameters when we calling drawmethod? example

DrawLineInt(Bitmap bmp);

this give the following error "The name 'e' does not exist in the current context "

"this give a error". What error? – Oded Jul 09 '12 at 20:48 — Oded, Jul 09 '12 at 20:48

score 33 · Accepted Answer · answered Jul 09 '12 at 21:16

"Draw a line on a bmp image which is pass into a method using drawline method in C#"

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.

To do this in a method, use @BFree's answer.

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:

http://msdn.microsoft.com/en-us/library/system.windows.forms.control.paint.aspx

You should also dispose your pen once you're done with it. Or put it inside a `using(var blackPen = new Pen(Color.Black, 3))` block. — Mateen Ulhaq, Apr 15 '16 at 21:21

score 6 · Answer 2 · answered Jul 09 '12 at 20:59

6

You need to get the Graphics object from the Image like so:

using(var graphics = Graphics.FromImage(bmp))
{
   graphics.DrawLine(...)
}

answered Jul 09 '12 at 20:59

BFree

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how to draw a line on a image?

2 Answers2

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