Disappearing Picturebox images [duplicate] - vb.net

Question

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Drawing Graphics Disappear in VB.net
(4 answers)
Closed 5 years ago.
I was successful in loading an image from a file into a picturebox in visual basic. Or so i thought. I had a msgbox in the code and the picture showed up in the picturebox. take the msgbox out and no picture. Any Ideas? Thanks
Private Sub DrawImageinSquarePanel(Panelname As PictureBox, ImageFile As String)
g = Panelname.CreateGraphics() 'creates new graphics element in panel
Dim newImage As Image = Image.FromFile(ImageFile) ' Create image.
Dim SquareDim As Integer 'Size of longest dimension in source image
If newImage.Width > newImage.Height Then
SquareDim = newImage.Width
Else
SquareDim = newImage.Height
End If
MsgBox(Panelname.Width & " " & Panelname.Height) 'the magic msgbox!!
' scale factor
Dim imageAttr As New ImageAttributes
imageAttr.SetGamma(Panelname.Width / SquareDim)
Dim ScaleFactor As Single = Panelname.Width / SquareDim
' Create rectangle for source and destination image.
Dim srcRect As New Rectangle(0, 0, newImage.Width, newImage.Height)
Dim destRect As New Rectangle((Panelname.Width - newImage.Width * ScaleFactor) / 2, (Panelname.Height - newImage.Height * ScaleFactor) / 2, newImage.Width * ScaleFactor, newImage.Height * ScaleFactor)
Dim units As GraphicsUnit = GraphicsUnit.Pixel
' Draw image to screen.
g.DrawImage(newImage, destRect, srcRect, units)
End Sub

Answer 1

Your title says "Picturebox" but there's no PictureBox there at all. If you want to display an Image in a PictureBox then assign the Image object to the Image property of that PictureBox.
Don't use GDI+ to draw it on a Panel and, if you ever do use GDI+ to draw, NEVER call CreateGraphics. Always draw on a control in its Paint event handler. The reason that your drawing disappears is that all drawing is erased on every Paint event. By doing your drawing in the Paint event handler, you ensure that it gets reinstated each time.
If you want to modify the image before displaying it then what you should do is create a new Bitmap object, use GDI+ to draw the modified image onto that and then assign that to the Image property of the PictureBox, e.g.
Using originalImage = Image.FromFile(filePath)
Dim newImage As New Bitmap(originalImage.Width, originalImage.Height)
Using g = Graphics.FromImage(newImage)
g.DrawImage(originalImage, Point.Empty)
End Using
'Dispose the existing image if there is one.
PictureBox1.Image?.Dispose()
PictureBox1.Image = newImage
End Using