trjhtr

This code is extremely slow and ideally I would appreciate someone walking me through getting this going on the GPU, but if nobody has time for that which is understandable, any and all optimisations would be most welcome!

Private Sub Picture(source As Image, picturebox As PictureBox)
 Dim r As Double
 Dim g As Double
 Dim b As Double

 Dim bmp As New Bitmap(source)
 Dim rect As New Rectangle(0, 0, bmp.Width, bmp.Height)
 Dim bmpData As System.Drawing.Imaging.BitmapData = bmp.LockBits(rect, System.Drawing.Imaging.ImageLockMode.[ReadOnly], bmp.PixelFormat)
 Dim ptr As IntPtr = bmpData.Scan0
 Dim bytes As Integer = bmpData.Stride * bmp.Height
 Dim rgbValues As Byte() = New Byte(bytes - 1) 
 System.Runtime.InteropServices.Marshal.Copy(ptr, rgbValues, 0, bytes)

 Dim linWhiteMult = 1 / (((LinearWhiteTextBox.Text * ((ShoulderStrengthTextBox.Text * LinearWhiteTextBox.Text) + (LinearAngleTextBox.Text * LinearStrengthTextBox.Text)) + (ToeStrengthTextBox.Text * ToeNumeratorTextBox.Text)) _
 / (LinearWhiteTextBox.Text * ((ShoulderStrengthTextBox.Text * LinearWhiteTextBox.Text) + LinearStrengthTextBox.Text) + ToeStrengthTextBox.Text * ToeDenominatorTextBox.Text) - (ToeNumeratorTextBox.Text / ToeDenominatorTextBox.Text)))

 'precalculations for optimisation

 Dim LaLs = LinearAngleTextBox.Text * LinearStrengthTextBox.Text
 Dim TsTn = ToeStrengthTextBox.Text * ToeNumeratorTextBox.Text
 Dim TsTd = ToeStrengthTextBox.Text * ToeDenominatorTextBox.Text
 Dim Tn_Td = ToeNumeratorTextBox.Text / ToeDenominatorTextBox.Text

 Dim list As New List(Of String)
 For x As Integer = 0 To bmp.Width - 1
 For y As Integer = 0 To bmp.Height - 1
 Dim position As Integer = (y * bmpData.Stride) + (x * Image.GetPixelFormatSize(bmpData.PixelFormat) / 8)
 b = rgbValues(position)
 g = rgbValues(position + 1)
 r = rgbValues(position + 2)

 '^2.2 lookup table (for optimisation) for gamma correction 

 b = table.Item(b)
 g = table.Item(g)
 r = table.Item(r)

'the following is the filmic tone map formula, i.e.
'x*(A*x+C*B)+D*E)/(x*(A*x+B)+D*F)) - E/F

 r = (((r * ((ShoulderStrengthTextBox.Text * r) + (LaLs)) + (TsTn)) _
 / (r * ((ShoulderStrengthTextBox.Text * r) + LinearStrengthTextBox.Text) + TsTd) - (Tn_Td))) * linWhiteMult

 g = (((g * ((ShoulderStrengthTextBox.Text * g) + (LaLs)) + (TsTn)) _
 / (g * ((ShoulderStrengthTextBox.Text * g) + LinearStrengthTextBox.Text) + TsTd) - (Tn_Td))) * linWhiteMult

 b = (((b * ((ShoulderStrengthTextBox.Text * b) + (LaLs)) + (TsTn)) _
 / (b * ((ShoulderStrengthTextBox.Text * b) + LinearStrengthTextBox.Text) + TsTd) - (Tn_Td))) * linWhiteMult
 If r > 1 Then
 r = 1
 End If
 If g > 1 Then
 g = 1
 End If
 If b > 1 Then
 b = 1
 End If

 rgbValues(position) = Math.Round((b ^ 0.45) * 255)
 rgbValues(position + 1) = Math.Round((g ^ 0.45) * 255)
 rgbValues(position + 2) = Math.Round((r ^ 0.45) * 255)

 Next
 Next

 System.Runtime.InteropServices.Marshal.Copy(rgbValues, 0, ptr, bytes)

 bmp.UnlockBits(bmpData)

 ' apply the bmp to the avatars and dispose old

 Dim OldImage = picturebox.Image
 picturebox.Image = bmp
 OldImage.Dispose()

End Sub

First, I have to say that your are using good variable name.

Turn Option Strick On

This setting is important, it'll help you see errors and needed conversion.

You'll notice that this isn't possible

Dim LaLs = LinearAngleTextBox.Text * LinearStrengthTextBox.Text

But instead you need to convert it to integer.

Dim LaLs = Int32.Parse(LinearAngleTextBox.Text) * Int32.Parse(LinearStrengthTextBox.Text)

Don't repeat yourself

You'll then notice that some conversion are done often.

Int32.Parse(LinearStrengthTextBox.Text)

Put these in proper variable right at the begining.

Dim linearStrength As Integer = Int32.Parse(LinearStrengthTextBox.Text)

There are formula like the below that are done in the inner loop, which can be moved outside of the loop.

(x * Image.GetPixelFormatSize(bmpData.PixelFormat) / 8)