Problem saving image after editing

[PeterJGibbins]

I have a program which edits image colour values.

Program works perfectly except that I can only save image to a new filename - I cannot overwrite the original file

Can anyone help?

ImageBitmap = New Bitmap(filename)
 
For x = 0 To ImageBitmap.Width - 1
    For y = 0 To ImageBitmap.Height - 1
        Rbyte = ImageBitmap.GetPixel(x, y).R
        Gbyte = ImageBitmap.GetPixel(x, y).G
        Bbyte = ImageBitmap.GetPixel(x, y).B
 
        '####  some byte manipulation
 
        ImageBitmap.SetPixel(x, y, Color.FromArgb(Rbyte, Gbyte, Bbyte))
    Next
Next
ImageBitmap.Save(filename, Imaging.ImageFormat.Png)  '### This throws an exception
 
 
#### if I change the filename and save as below - everything OK
filename2 = Mid(filename, 1, Len(filename) - 4) & "2.png"
ImageBitmap.Save(filename2, Imaging.ImageFormat.Png)  '### This works perfectly

[Frinavale]

Have you tried adding a check to see if the file exists first (which it should because you read from it)?

If it exists, try to delete it and recreate it.

[PeterJGibbins]

I know the file exists because I have edited it...

However - you made me think...
I have tried to delete the file while my program is running and got
"Action cannot be completed because file is open in vhost32.exe"

Obviously I can't create a file which already exists and is open..
but bitmap does not give the option to close a file and save won't overwrite........??

[IronRazer]

This happens when you create a new bitmap from an image file because, it does not released the reference to the file until you call the Dispose method of the new Bitmap.

You can get around it in several ways. One is to create a temporary Bitmap with a Using/End Using statement to open the image file and create the new Bitmap from that Bitmap. The temporary Bitmap will be disposed when the End Using statement is executed which will release all references to the image file.

Then you can overwrite the original image with the modified Bitmap.

Public Class Form1
    Private filename As String = "C:\TestFolder\MyLogo.png"
 
    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Dim Rbyte, Gbyte, Bbyte As Byte
 
        Dim ImageBitmap As Bitmap = Nothing
        Using bm As New Bitmap(filename)
            ImageBitmap = New Bitmap(bm)
        End Using
 
        For x As Integer = 0 To ImageBitmap.Width - 1
            For y As Integer = 0 To ImageBitmap.Height - 1
                Rbyte = ImageBitmap.GetPixel(x, y).R
                Gbyte = ImageBitmap.GetPixel(x, y).G
                Bbyte = ImageBitmap.GetPixel(x, y).B
 
                '####  some byte manipulation
 
                ImageBitmap.SetPixel(x, y, Color.FromArgb(Rbyte, Gbyte, Bbyte))
            Next
        Next
        ImageBitmap.Save(filename, Imaging.ImageFormat.Png)
        ImageBitmap.Dispose() 'dispose this new Bitmap when it is not needed anymore
 
    End Sub
End Class
 

[PeterJGibbins]

Strange....
Still no luck.....
I'd already tried copying to a temp bitmap and using dispose -
but have tried <Using> <End using> copied from you example - same error

Checked by trying to access file using windows explorer after image loaded and end using had run (used msgbox as marker)
file was still open in host32.exe - so not released.

Any idea on how to force a "Flush"?

[PeterJGibbins]

Iron Razor

Using the temp bitmap didn't work BUT io.filestream example DID

 Using fs As New IO.FileStream(filename, IO.FileMode.Open)
            NormalisedImage = New Bitmap(fs)
 End Using

This worked perfectly
Problem solved - Many Thanks for the advice
Peter