Preventing Image.FromFile exception in VB 2022 when the file does not have a valid image format

You can check image formats with "Magic Numbers"

I did this test, with the help of ChatGPT =>

  Class ByteArrayComparer
        Implements IEqualityComparer(Of Byte())

        Public Shadows Function Equals(x() As Byte, y() As Byte) As Boolean Implements IEqualityComparer(Of Byte()).Equals
            Return x.SequenceEqual(y)
        End Function

        Public Shadows Function GetHashCode(obj() As Byte) As Integer Implements IEqualityComparer(Of Byte()).GetHashCode
            Dim hash As Long = 17
            For Each b In obj
                hash = hash * 31 + b
            Next
            Return hash And &H7FFFFFFF ' truncate safely to positive 32-bit integer
        End Function

    End Class

    Function IsSupportedImageFormat(path As String, ByRef format As String) As Boolean
        format = Nothing

        Dim signatures As New Dictionary(Of Byte(), String)(New ByteArrayComparer) From {
        {New Byte() {&HFF, &HD8, &HFF}, "JPEG"},
        {New Byte() {&H89, &H50, &H4E, &H47, &HD, &HA, &H1A, &HA}, "PNG"},
        {System.Text.Encoding.ASCII.GetBytes("GIF87a"), "GIF"},
        {System.Text.Encoding.ASCII.GetBytes("GIF89a"), "GIF"},
        {System.Text.Encoding.ASCII.GetBytes("BM"), "BMP"},
        {New Byte() {&H49, &H49, &H2A, &H0}, "TIFF (LE)"},
        {New Byte() {&H4D, &H4D, &H0, &H2A}, "TIFF (BE)"},
        {New Byte() {&H0, &H0, &H1, &H0}, "ICO"},
        {New Byte() {&HD7, &HCD, &HC6, &H9A}, "WMF"}
    }

        Try
            Using fs As New FileStream(path, FileMode.Open, FileAccess.Read)
                Dim buffer(255) As Byte
                fs.Read(buffer, 0, buffer.Length)

                ' Detect standard formats
                For Each kvp In signatures
                    Dim sig = kvp.Key
                    Dim name = kvp.Value

                    If buffer.Take(sig.Length).SequenceEqual(sig) Then
                        format = name
                        Return True
                    End If
                Next
               
                ' Detect EMF (look for EMR_HEADER at the beginning and optional " EMF" string at offset 40)
                If buffer.Length >= 44 AndAlso buffer(0) = &H1 AndAlso buffer(1) = 0 AndAlso buffer(2) = 0 AndAlso buffer(3) = 0 Then
                    ' Optional check for " EMF" at offset 40
                    If buffer(40) = Asc(" ") AndAlso buffer(41) = Asc("E") AndAlso buffer(42) = Asc("M") AndAlso buffer(43) = Asc("F") Then
                        format = "EMF"
                        Return True
                    Else
                        ' Still likely EMF without " EMF" string
                        format = "EMF"
                        Return True
                    End If
                End If
            End Using
        Catch
            format = Nothing
            Return False
        End Try

        Return False
    End Function

Thanks for your response.

I have learned a good deal since I posted the question.

Other apps (IrfanView, Photoshop) are able to open and display the image files that Image.FromFile and MS Photo Viewer cannot.

I opened one file in PS Elements and saved it with a new name; VB and Photo Viewer can read and display it.

I will take a good look at your code and may incorporate it in my app, but it looks as if the Microsoft software is falsely reporting corruption in good files.