Question

I have a function in my VB project where i scan an image and then I can change the contrast.
I scan it and saves it C:\temp\my_img.tif.

In the winform the image is displayed in a PictureBox.

If I in the contrast function set like img.Save("C:\temp\my_img.tif", ImageFormat.Tiff) I get “A generic error occurred in GDI+.”. If I however set the filename to something else, it works just fine.

So, how do I release the used image before saving it?

The whole function, in short:

Sub setContrast(ByVal C As Single)
    'filename(1) ia a "global" variable that stores the used file path, in this case "C:\temp\my_img.tif"

    Dim img As Image = Image.FromFile(filename(1)) '<--- I get the image

    'A bunch of contrast stuff in some rows.....

    'Here, i should release the image...

    img.Save(filename(1), ImageFormat.Tiff) '<---Tries to save

    PictureBox1.Refresh()
End Sub

Answer 1

Save it using a different file name, and then, if necessary, delete the old file and rename the new file to match the old, having Disposed of the Image beforehand.

From Image.FromFile:

The file remains locked until the Image is disposed.

There’s no wording anywhere else that says that this is somehow worked around if the same Image instance is trying to Save back to the file.