[vb .net] Resize Image

[bangbang023 Veteran]

I have an image declared as

dim backImage as image

I then apply this image to the background of a form. However when the form resize's I wan tto resize the image and then re-apply it. How can i resize the image? the size property (bakImage.size) is readonly.

[fdjfdijsfsdf]

Well i have never used .NET but i use VB6 and i dont know if its similar..

do you have a form_resize event? if so then do that.. then in VB you can do

BackImage.Move 0, 0, ScaleWidth, ScaleHeight

Dont know if that helps

[bangbang023 Veteran]

thanks for the try but that doesn't work in vb .net

[fdjfdijsfsdf]

oh. shame :(

[NXPdev]

You will have to recreate the image to the new size and then paint it back on.

Dim imgBuffer As New Bitmap(Me.Size)
imgBuffer.CreateGraphics.DrawImage(backImage, 0, 0, Me.Size)
Me.BackgroundImage = imgBuffer
imgBuffer.Dispose

(Excuse errors, this is from the top of my head.)

[bangbang023 Veteran]

sorry not working, that may be vb6 code

[NXPdev]

It needs fixing! It was from the top of my head... and I don't have VS installed yet (just reformatted).

[bangbang023 Veteran]

if it needs fixing, I have no idea what to fix because first off I'm not using bitmaps although maybe with new bitmap i don't have to. Also there is no such thing under system.drawing for creategraphics and it also says no image accepts that many arguments.

[bangbang023 Veteran]

i am trying ot use this for the resize event, but the form just disappears then, but i think this is the right track:

       backImage = New System.Drawing.Bitmap(Me.Width, Me.Height).FromFile("Skins\" & skinChoice & "\background.jpg"
        backImage = Bitmap.FromFile("Skins\" & skinChoice & "\background.jpg")
        Me.BackgroundImage = backImage

[noll3095]

Try this for the paint and resize events (C# of course):

private void Form1_Paint(object sender, System.Windows.Forms.PaintEventArgs e)
{
	Graphics g = e.Graphics;
	Bitmap bmp = new Bitmap("Lightening.jpg");
	Rectangle r = new Rectangle(0,0,bmp.Width,bmp.Height);
	g.DrawImage(bmp,this.ClientRectangle);
}

private void Form1_Resize(object sender, System.EventArgs e)
{
	this.Invalidate();
}

[bangbang023 Veteran]

thanks noah, you rule as usual

[azcodemonkey]

You're probably going to get a lot of flicker. Forms, and I believe most controls don't support double buffering by default.

I made an example project a bit ago that demonstrated how to resize a bitmap by subclassing a panel control and making it double buffer by using the SetStyle method of the control.

Public Class UserPanel
 ?Inherits System.Windows.Forms.Panel

#Region " Windows Form Designer generated code "

 ? ?Public Sub New()
 ? ? ? ?MyBase.New()

 ? ? ? ?'This call is required by the Windows Form Designer.
 ? ? ? ?InitializeComponent()
 ? ?Me.SetStyle(ControlStyles.AllPaintingInWmPaint Or _
 ? ? ? ? ControlStyles.UserPaint Or _
 ? ? ? ?ControlStyles.DoubleBuffer, True)

 ? ? ? ?'Add any initialization after the InitializeComponent() call

 ? ?End Sub

 ? ?'UserControl overrides dispose to clean up the component list.
 ? ?Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
 ? ? ? ?If disposing Then
 ? ? ? ? ? ?If Not (components Is Nothing) Then
 ? ? ? ? ? ? ? ?components.Dispose()
 ? ? ? ? ? ?End If
 ? ? ? ?End If
 ? ? ? ?MyBase.Dispose(disposing)
 ? ?End Sub

 ? ?'Required by the Windows Form Designer
 ? ?Private components As System.ComponentModel.IContainer

 ? ?'NOTE: The following procedure is required by the Windows Form Designer
 ? ?'It can be modified using the Windows Form Designer. ?
 ? ?'Do not modify it using the code editor.
 ? ?<System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()
 ? ? ? ?components = New System.ComponentModel.Container()
 ? ?End Sub

#End Region

End Class

Then, use the code that noll presented, except handle the panel's paint and resize events, and you'll probably want to make your image a class variable instead of creating it each time the form paints.

? ? ? ?img = Image.FromFile("animage.jpg") ' or whatever
 ? ? ? ?panel = New UserPanel
 ? ? ? ?lbl = New Label
 ? ? ? ?'This call is required by the Windows Form Designer.
 ? ? ? ?InitializeComponent()
 ? ? ? ?AddHandler panel.Paint, AddressOf panel_OnPaint
 ? ? ? ?AddHandler panel.Resize, AddressOf panel_OnResize

 ? ? ? ?' add the control to the form
 ? ? ? ?Me.Controls.Add(panel)

 ? ? ? ?'.... other form code

 ? ?Private Sub panel_OnPaint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs)
 ? ? ? ?Dim rect As New Rectangle(0, 0, panel.Width, panel.Height)
 ? ? ? ?e.Graphics.DrawImage(img, rect, 0, 0, img.Width, img.Height, GraphicsUnit.Pixel)
 ? ?End Sub

 ? ?Private Sub panel_OnResize(ByVal sender As Object, ByVal e As System.EventArgs)
 ? ? ? ?panel.Invalidate()
 ? ?End Sub

[Steven]

Could you use "BeginUpdate" & "EndUpdate" to help the flicker? or those are only usable in the combobox and listbox and treeview controls.

[azcodemonkey]

Not 100% sure, but I think those apply only to the controls you mentioned.

[bangbang023 Veteran]

thanks weenur but the form is very simple and noah's code is perfect for what i wound up doing. i didn't like having a window border around a skinned window, so instead, I have it where the user can override the default skin set size but going into the config panel and entering the new values, a little less functional but works well enough.

[NXPdev]

To prevent flicker, override the OnBackgroundPaint event.

[noll3095]

Actually, it's much easier to use double buffering as it's supported directly by GDI+. To enable it, insert these three lines of code in the load event for the form:

this.SetStyle(ControlStyles.DoubleBuffer,true);
this.SetStyle(ControlStyles.AllPaintingInWmPaint,true);
this.SetStyle(ControlStyles.UserPaint,true);

Substitute VB for the C# and you should be flicker free.

[azcodemonkey]

I tried that once before and it didn't work. I guess I'll try it again. Thanks noll.