Question Faster way to convert a Bitmap from Format1bppIndexed to Format32bppArgb

[j_t]

I have been trying to find a faster way to convert a Format1bppIndexed bitmap to a Format32bppArgb.

Anyone have any ideas of a faster method?

Here the results/output:

orgBitmap.PixelFormat = Format1bppIndexed
Resolution = 200 Physical Size 1178 x 1653
-- Converting Image... --
ConvertToRGB [ Graphics.DrawImageUnscaled ] - 96 mils
ConvertToRGB2 [ Clone Bitmap ] - 67 mils
ConvertToRGB3 [ Lockbits / Marshal.Copy ] - 84 mils
NEW Bitmap.PixelFormat = Format32bppArgb

Here is my code:

   Public Function ConvertToRGB(ByVal original As Bitmap) As Bitmap

        Dim sw As New Stopwatch
        sw.Start()

        Dim newImage As New Bitmap(original.Width, original.Height, PixelFormat.Format32bppArgb)

        newImage.SetResolution(original.HorizontalResolution, original.VerticalResolution)

        Dim g As Graphics = Graphics.FromImage(newImage)

        g.CompositingQuality = Drawing2D.CompositingQuality.HighSpeed
        g.InterpolationMode = Drawing2D.InterpolationMode.Low
        g.SmoothingMode = Drawing2D.SmoothingMode.None
        
        g.DrawImageUnscaled(original, 0, 0)

        sw.Stop()
        Debug.Print("ConvertToRGB  [ Graphics.DrawImageUnscaled ] - " & sw.ElapsedMilliseconds & " mils")

        If newImage.PixelFormat <> PixelFormat.Format32bppArgb Then Debug.Print("WRONG FORMAT - newImage.PixelFormat = " & [Enum].GetName(GetType(PixelFormat), newImage.PixelFormat))

        Return newImage


    End Function

    Public Function ConvertToRGB2(ByVal original As Bitmap) As Bitmap

        Dim sw As New Stopwatch
        sw.Start()

        '' Note: This method does not work on Windows XP. Hmmm...

        Dim newImage As Bitmap = Nothing
        newImage = original.Clone(New Rectangle(0, 0, original.Width, original.Height), PixelFormat.Format32bppArgb)

        newImage.SetResolution(original.HorizontalResolution, original.VerticalResolution)

        sw.Stop()
        Debug.Print("ConvertToRGB2 [ Clone Bitmap               ] - " & sw.ElapsedMilliseconds & " mils")

        If newImage.PixelFormat <> PixelFormat.Format32bppArgb Then Debug.Print("WRONG FORMAT - newImage.PixelFormat = " & [Enum].GetName(GetType(PixelFormat), newImage.PixelFormat))

        Return newImage

    End Function


    Public Function ConvertToRGB3(ByVal original As Bitmap) As Bitmap

        Dim sw As New Stopwatch
        sw.Start()

        ' Lock source bitmap in memory
        Dim sourceData As BitmapData = original.LockBits(New Rectangle(0, 0, original.Width, original.Height), ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb)
        Dim imageSize As Integer = sourceData.Stride * sourceData.Height

        ' Create destination bitmap
        Dim newImage As Bitmap = New Bitmap(original.Width, original.Height, PixelFormat.Format32bppArgb)
        newImage.SetResolution(original.HorizontalResolution, original.VerticalResolution)
        Dim sourceBuffer(imageSize) As Byte
        Marshal.Copy(sourceData.Scan0, sourceBuffer, 0, imageSize)
        ' Unlock source bitmap
        original.UnlockBits(sourceData)

        ' Lock destination bitmap in memory
        Dim destinationData As BitmapData = newImage.LockBits(New Rectangle(0, 0, newImage.Width, newImage.Height), ImageLockMode.WriteOnly, PixelFormat.Format32bppArgb)

        ' Copy binary image data to destination bitmap
        Marshal.Copy(sourceBuffer, 0, destinationData.Scan0, imageSize)

        ' Unlock destination bitmap
        newImage.UnlockBits(destinationData)

        newImage.SetResolution(original.HorizontalResolution, original.VerticalResolution)
        sw.Stop()
        Debug.Print("ConvertToRGB3 [ Lockbits / Marshal.Copy    ] - " & sw.ElapsedMilliseconds & " mils")

        If newImage.PixelFormat <> PixelFormat.Format32bppArgb Then Debug.Print("WRONG FORMAT - newImage.PixelFormat = " & [Enum].GetName(GetType(PixelFormat), newImage.PixelFormat))

        Return newImage

    End Function