Draw bitmap in memory, then display

[jhasty]

I am trying to figure out how to draw simple lines on a bitmap in memory, then display the bitmap on a control (probably a PictureBox). I also need to be able to save the memory bitmap to a .bmp file. I'm using VB .NET.

 

I have been completely unable to figure out how to set up the various objects to do this. BitMap? Image? Graphics? I am so lost.

 

If someone could show me a simple example, I think I could figure it out from there. How about an example that would create a bitmap in memory, draw a line on the bitmap, and then show the bitmap on a PictureBox control?

 

Any help would be greatly appreciated.

[divil]

This example shows creating an in-memory bitmap, drawing a circle on it, then assigning the bitmap to a picturebox.

 

   Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
       Dim b As New Bitmap(100, 100)
       Dim g As Graphics = Graphics.FromImage(b)

       g.DrawEllipse(Pens.Red, New RectangleF(0, 0, b.Width, b.Height))

       PictureBox1.Image = b
       'b.Save("c:\temp.bmp")

       g.Dispose()
   End Sub

 

If you uncomment the commented line, the bitmap will be saved to the hard disk.

[chuawenching]

Hi

 

Hi..

 

just wonder i draw a circle in the picturebox1

 

1) and i want to store the circle in memory (only circle)

 

when i store into bmp...

 

i want to see the circle with transparent backrground...

 

i need to do some image processing?

 

The way on top works, just not sure does it store with the background color or image together?

 

2) Just wondering, if 1 drag 1 circle...

 

i want to calculate the x,y of the circle...

 

maybe 1 circle with 10 nodes of (x,y) and store in array

 

how can i do that?

 

Any help?

 

Regards,

Chua Wen Ching :p

[Diablicolic]

Divil when I use that code, the Graphics thing in the declaring gets highlighted in red. I don't understand the error but when I check it out it says that "Type Expected"...what does that mean?

[AndreRyan]

Does you're project import System.Drawing, if it does change it to System.Drawing.Graphics.FromImage(b).

 

1) I think you're asking how to make the background transparent? Put b.MakeTransparent(Color.White) before saving, you may also need to save it as a picture format that allows transparency like GIF

[Volte]

Divil when I use that code, the Graphics thing in the declaring gets highlighted in red. I don't understand the error but when I check it out it says that "Type Expected"...what does that mean?

Are you using VB.NET?? :confused:

[chuawenching]

Is Andre refering to me or the original poster?

 

Regards,

Chua Wen Ching :p

[chuawenching]

Help

 

This example shows creating an in-memory bitmap, drawing a circle on it, then assigning the bitmap to a picturebox.

 

   Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
       Dim b As New Bitmap(100, 100)
       Dim g As Graphics = Graphics.FromImage(b)

       g.DrawEllipse(Pens.Red, New RectangleF(0, 0, b.Width, b.Height))

       PictureBox1.Image = b
       'b.Save("c:\temp.bmp")

       g.Dispose()
   End Sub

 

If you uncomment the commented line, the bitmap will be saved to the hard disk.

 

Any idea how that code works in c#?

 

the b.width - i can't find the width!

 

and i cannot place b into FromImage(b) // invalid arguments

 

C:\WenChing\Store Image in Memory\Form1.cs(94): Argument '1': cannot convert from 'System.Drawing.Bitmap[*,*]' to 'System.Drawing.Image'

 

 

Any help?

 

Regards,

Chua Wen Ching :p

[AndreRyan]

       Bitmap b = New Bitmap(100, 100);
       Graphics g = Graphics.FromImage(b);

       g.DrawEllipse(Pens.Red, New RectangleF(0, 0, b.Width, b.Height));

       g.Dispose();

       //b.MakeTransparent(Color.White);
       PictureBox1.Image = b;
       //b.Save("c:\temp.bmp");

I'm not skilled in C#, I have no liking for C syntax but I think this right

[chuawenching]

Nope it is not right!

 

when i click on b. (intellisense show) and i can't find width!

 

Regards,

Chua Wen Ching :p

[AndreRyan]

I just checked it in C# and this worked:

Bitmap b = new Bitmap(100, 100);
       Graphics g = Graphics.FromImage(b);

       g.DrawEllipse(Pens.Red, 0, 0, b.Width, b.Height);

       g.Dispose();

       //b.MakeTransparent(Color.White);
       this.pictureBox1.Image= b;
       //b.Save("c:\temp.bmp");

The thing I really hate in C syntax is that it's case sensitive, that's what always gets me, capitals when they should be lowercase. Whats the point of having a variable named Var1 and var1 or New must be new. It's just confusing

Edited July 29, 2003 by AndreRyan