How to resize the bitmap used for Paint event

[active]

This is what I do in a PictureBox New:
b1 = New Drawing.Bitmap( Width, Height, Me.CreateGraphi cs())

g1 = Graphics.FromIm age(b1)

Someplace I do

g1.DrawString.. .......

Then in Paint I do:

e.Graphics.Draw Image(b1, 0, 0)

Do I have to do something in Dispose??

What should I do if the Box is resized??

Thanks

Cal

[Armin Zingler]

" active" <ac****@REMOV Ea-znet.com> schrieb

This is what I do in a PictureBox New:
b1 = New Drawing.Bitmap( Width, Height, Me.CreateGraphi cs())

g1 = Graphics.FromIm age(b1)

I guess you declared g1 and b1 at class level? (a field in the class)

In Sub New I'd probably write

dim g as graphics
g = me.creategraphi cs
b1 = New Drawing.Bitmap( Width, Height, g)
g.dispose '<- dispose here
g1 = Graphics.FromIm age(b1)
'...

Someplace I do

g1.DrawString.. .......

Then in Paint I do:

e.Graphics.Draw Image(b1, 0, 0)

Do I have to do something in Dispose??
I'd call g1.dispose and b1.dispose.
What should I do if the Box is resized??

I'd call g1.dispose, b1.dispose and recreate the bitmap. So, the Bitmap
creating lines should be a separate proc called from the ctor and in
OnResize.
--
Armin

http://www.plig.net/nnq/nquote.html
http://www.netmeister.org/news/learn2quote.html

[active]

I realize that the quick test I had did seemed to work but it was not
correct.
I have a usercontrol containing a picturebox that I want to draw on.
What happens is I'm drawing on the UserControl instead.

I guess you declared g1 and b1 at class level? (a field in the class)

In Sub New I'd probably write

dim g as graphics
g = me.creategraphi cs
can't use g1 here? Why do we need g? b1 = New Drawing.Bitmap( Width, Height, g)
I don't understand why dispose and then get a new one.
What is this for?? g.dispose '<- dispose here
g1 = Graphics.FromIm age(b1)
'...

What should I do if the Box is resized??

I'd call g1.dispose, b1.dispose and recreate the bitmap. So, the Bitmap
creating lines should be a separate proc called from the ctor and in
OnResize.

recreate the graphics in the bitmap is not possible. Think of Photoshop and
the user resizes after drawing.
Thanks for helping,
Cal

[Armin Zingler]

" active" <ac****@REMOV Ea-znet.com> schrieb

I realize that the quick test I had did seemed to work but it was
not correct.
I have a usercontrol containing a picturebox that I want to draw
on. What happens is I'm drawing on the UserControl instead.

Then you can paint in the Picturebox' paint event.

An alternative is to derive your own class from the Picturebox class and
override OnPaint - but currently this does not make the difference.

I guess you declared g1 and b1 at class level? (a field in the
class)

In Sub New I'd probably write

dim g as graphics
g = me.creategraphi cs

can't use g1 here? Why do we need g?

It was _you_ who created a new Graphics object. In your first posting you
wrote

b1 = New Drawing.Bitmap( Width, Height, Me.CreateGraphi cs())

I changed this and assigned the return value of Me.CreateGraphi cs to the
variable to be able to call the Dispose method afterwards.

b1 = New Drawing.Bitmap( Width, Height, g)

I don't understand why dispose and then get a new one.
What is this for??

g.dispose '<- dispose here
g1 = Graphics.FromIm age(b1)
See comment above: You also created two Graphics objects. I guess you did it
because you wanted this for the reason described in the documentation for
the constructor when passing a graphics object: The resolution of the
graphics object is applied to the bitmap.

What should I do if the Box is resized??

I'd call g1.dispose, b1.dispose and recreate the bitmap. So, the
Bitmap creating lines should be a separate proc called from the
ctor and in OnResize.

recreate the graphics in the bitmap is not possible. Think of
Photoshop and the user resizes after drawing.

What does this mean? You can copy the old Bitmap into the new Bitmap if you
don't want to loose the content.
--
Armin

http://www.plig.net/nnq/nquote.html
http://www.netmeister.org/news/learn2quote.html

[active]

Then you can paint in the Picturebox' paint event. I had figured that out and it makes sense and works OK.

dim g as graphics
g = me.creategraphi cs

can't use g1 here? Why do we need g?

It was _you_ who created a new Graphics object. In your first posting you
wrote

b1 = New Drawing.Bitmap( Width, Height, Me.CreateGraphi cs())

I changed this and assigned the return value of Me.CreateGraphi cs to the
variable to be able to call the Dispose method afterwards.

Got it! Thanks

> What should I do if the Box is resized??

recreate the graphics in the bitmap is not possible. Think of
Photoshop and the user resizes after drawing.

What does this mean? You can copy the old Bitmap into the new Bitmap if

you don't want to loose the content.
Sounds good to me. thanks

Thank a lot
Cal

[Herfried K. Wagner [MVP]]

* " active" <ac****@REMOV Ea-znet.com> scripsit:

This is what I do in a PictureBox New:
b1 = New Drawing.Bitmap( Width, Height, Me.CreateGraphi cs())

g1 = Graphics.FromIm age(b1)

Someplace I do

g1.DrawString.. .......

Then in Paint I do:

e.Graphics.Draw Image(b1, 0, 0)

Do I have to do something in Dispose??
You will have to dispose 'g1'.

\\\
g1.Dispose()
///
What should I do if the Box is resized??

Who knows what you want to do?

--
Herfried K. Wagner [MVP]
<http://www.mvps.org/dotnet>