Preventing Picture Clearing in VB.Net Program on PictureBox

[JasonRox]

Hey guys,

Working on a program.

My program mostly takes place on a Picture Box where a user can click the picture in different areas and different images and sentences and words come up.

Hence, I used the following often...

g = PictureBox1.CreateGraphics()
g.DrawString("Hello World", font, brush, 50, 50)

But the images clear if the box is moved over anything. Hence a user who's playing and then decides to send a message to his friend will have his Picture cleared. How can I keep this from happening?

 

[DavidSnider]

Hey guys,

Working on a program.

My program mostly takes place on a Picture Box where a user can click the picture in different areas and different images and sentences and words come up.

Hence, I used the following often...

g = PictureBox1.CreateGraphics()
g.DrawString("Hello World", font, brush, 50, 50)

But the images clear if the box is moved over anything. Hence a user who's playing and then decides to send a message to his friend will have his Picture cleared. How can I keep this from happening?

Are you redrawing the box when it gets moved?

 

[JasonRox]

Are you redrawing the box when it gets moved?

Oh no, the stuff is already plotted.

THen you move it, and it gets erased and the default picture is shown.

 

[DavidSnider]

Try drawing to an in-memory bitmap and then on the OnDraw event of the picturebox set the picturebox bitmap to the memory bitmap.

 

[TurtleMeister]

You need to have a "paint event" for the picture box and draw the string there. That way any time the picture box redrawn your text will be redrawn also. Example:

Private Sub PictureBox1_Paint(ByVal sender As System.Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles PictureBox1.Paint

        e.Graphics.DrawString("Hello world", Font, brush, 50, 50)

End Sub

 

[JasonRox]

You need to have a "paint event" for the picture box and draw the string there. That way any time the picture box redrawn your text will be redrawn also. Example:

Private Sub PictureBox1_Paint(ByVal sender As System.Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles PictureBox1.Paint

        e.Graphics.DrawString("Hello world", Font, brush, 50, 50)

End Sub

Well, then this draws it right away. Here is an idea of what I'm doing...

Private Sub PictureBox1_MouseDown(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles PictureBox1.MouseDown

g.Drawstring("Hello World!", font, brush, 50, 50)

End Sub

So, the event only occurs if they click on it

 

[JasonRox]

Try drawing to an in-memory bitmap and then on the OnDraw event of the picturebox set the picturebox bitmap to the memory bitmap.

I tried doing that before and my code always had errors.

 

[TurtleMeister]

You can use logic in the paint event.

Private Sub PictureBox1_MouseDown(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles PictureBox1.MouseDown

        PaintMyString = True

End Sub

Private Sub PictureBox1_Paint(ByVal sender As System.Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles PictureBox1.Paint

        If PaintMyString = True Then
            e.Graphics.DrawString("Hello world", Font1, Brushes.Black, 20, 20)
        End If

End Sub

 

[DavidSnider]

I don't think you want to redraw the memory bitmap every time Paint is called (unless your image is dynamic in some way). I'd draw it to memory once and then redraw the bitmap.

DrawString takes a lot of cycles compared to a plain ol' blit.

 

[JasonRox]

I don't think you want to redraw the memory bitmap every time Paint is called (unless your image is dynamic in some way). I'd draw it to memory once and then redraw the bitmap.

DrawString takes a lot of cycles compared to a plain ol' blit.

I have no idea how to do even that.

 

[TurtleMeister]

I think this method will accomplish what DavidSnider is talking about. Put the code in your mousedown event.

g = Graphics.FromImage(PictureBox1.Image)
g.DrawString("Hello World", font, brush, 50, 50)
PictureBox1.Refresh()

 

[JasonRox]

I think this method will accomplish what DavidSnider is talking about. Put the code in your mousedown event.

g = Graphics.FromImage(PictureBox1.Image)
g.DrawString("Hello World", font, brush, 50, 50)
PictureBox1.Refresh()

I'm going to try that out. Thanks!