Color Scale Filter

' Class implementing grayscale conversion of color image.
' 
' Copyright (c) 2007 Miran Uhan
' 
' This program is free software; you can redistribute it and/or modify
' it under the terms of the GNU General Public License as published by
' the Free Software Foundation; either version 2 of the License, or
' (at your option) any later version.
'
' This program is distributed in the hope that it will be useful,
' but WITHOUT ANY WARRANTY; without even the implied warranty of
' MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
' GNU General Public License for more details.
'
' You should have received a copy of the GNU General Public License
' along with this program; if not, write to the
'    Free Software Foundation, Inc.
'    51 Franklin Street, Fifth Floor
'    Boston, MA 02110-1301 USA
'
' Sources:
' - http://www.codeproject.com/cs/library/yael_image_filters.asp
' - http://www.bobpowell.net/grayscale.htm
'
' For questions you can contact author at
'    miran.uhan@gmail.com
' Sugestions and bug reports are also welcome.
' 

Imports System.Drawing
Imports System.Drawing.Imaging

Public Class GrayScaleFilter
   Inherits BasicFilter

   Private _brightness As Brightness = Brightness.Normal
   Private _useColorMatrix As Boolean = False
   Private _factorRed As Integer = 30
   Private _factorGreen As Integer = 59
   Private _factorBlue As Integer = 11

   ''' <summary>
   ''' Get or set brightness.
   ''' </summary>
   ''' <value></value>
   ''' <returns></returns>
   ''' <remarks></remarks>
   Public Property Brightness() As Brightness
      Get
         Return _brightness
      End Get
      Set(ByVal value As Brightness)
         _brightness = value
         Select Case _brightness
            Case Brightness.Normal
               _factorRed = 30
               _factorGreen = 59
               _factorBlue = 11
            Case Brightness.Bright
               _factorRed = 50
               _factorGreen = 50
               _factorBlue = 50
         End Select
      End Set
   End Property

   ''' <summary>
   ''' Get or set factor for red component.
   ''' </summary>
   ''' <value>Integer in range [0..100].</value>
   ''' <returns></returns>
   ''' <remarks></remarks>
   Public Property FactorRed() As Integer
      Get
         Return _factorRed
      End Get
      Set(ByVal value As Integer)
         If ((value >= 0) And (value <= 100)) Then
            _factorRed = value
         End If
      End Set
   End Property

   ''' <summary>
   ''' Get or set factor for green component.
   ''' </summary>
   ''' <value>Integer in range [0..100].</value>
   ''' <returns></returns>
   ''' <remarks></remarks>
   Public Property FactorGreen() As Integer
      Get
         Return _factorGreen
      End Get
      Set(ByVal value As Integer)
         If ((value >= 0) And (value <= 100)) Then
            _factorGreen = value
         End If
      End Set
   End Property

   ''' <summary>
   ''' Get or set factor for blue component.
   ''' </summary>
   ''' <value>Integer in range [0..100].</value>
   ''' <returns></returns>
   ''' <remarks></remarks>
   Public Property FactorBlue() As Integer
      Get
         Return _factorBlue
      End Get
      Set(ByVal value As Integer)
         If ((value >= 0) And (value <= 100)) Then
            _factorBlue = value
         End If
      End Set
   End Property

   ''' <summary>
   ''' Get or set color matrix use flag.
   ''' </summary>
   ''' <value></value>
   ''' <returns></returns>
   ''' <remarks></remarks>
   Public Property UseColorMatrix() As Boolean
      Get
         Return _useColorMatrix
      End Get
      Set(ByVal value As Boolean)
         _useColorMatrix = value
      End Set
   End Property

   ''' <summary>
   ''' Execute filter and return filtered image.
   ''' </summary>
   ''' <param name="img"></param>
   ''' <returns></returns>
   ''' <remarks></remarks>
   Public Overrides Function ExecuteFilter( _
            ByVal img As System.Drawing.Image) As System.Drawing.Image
      Select Case img.PixelFormat
         Case PixelFormat.Format16bppGrayScale
            Return img
         Case PixelFormat.Format24bppRgb, _
                  PixelFormat.Format32bppArgb, PixelFormat.Format32bppRgb
            If _useColorMatrix Then
               Return ExecuteRgb8Matrix(img)
            Else
               Return ExecuteRgb8(img)
            End If
         Case PixelFormat.Format48bppRgb
            Return img
         Case Else
            Return img
      End Select
   End Function

   ''' <summary>
   ''' Execute filter on (A)RGB image with 8 bits per color.
   ''' </summary>
   ''' <param name="img"></param>
   ''' <returns></returns>
   ''' <remarks></remarks>
   Public Function ExecuteRgb8( _
            ByVal img As System.Drawing.Image) As System.Drawing.Image
      Dim result As Bitmap = New Bitmap(img)
      Dim bmpData As BitmapData = result.LockBits( _
                     New Rectangle(0, 0, result.Width, result.Height), _
                     ImageLockMode.ReadWrite, img.PixelFormat)
      Dim pixelBytes As Integer = _
               System.Drawing.Image.GetPixelFormatSize(img.PixelFormat) \ 8
      'Get the address of the first line.
      Dim ptr As IntPtr = bmpData.Scan0
      Dim size As Integer = bmpData.Stride * result.Height
      Dim pixels(size - 1) As Byte
      Dim index As Integer
      Dim Y As Integer
      Dim mulR As Double = _factorRed / 100
      Dim mulG As Double = _factorGreen / 100
      Dim mulB As Double = _factorBlue / 100
      'Copy the RGB values into the array.
      System.Runtime.InteropServices.Marshal.Copy(ptr, pixels, 0, size)
      'Main loop.
      For row As Integer = 0 To result.Height - 1
         For col As Integer = 0 To result.Width - 1
            index = (row * bmpData.Stride) + (col * pixelBytes)
            Y = CInt(System.Math.Round( _
                     mulR * pixels(index + 2) + _
                     mulG * pixels(index + 1) + _
                     mulB * pixels(index + 0)))
            If (Y > 255) Then Y = 255
            'Save new values.
            pixels(index + 2) = CByte(Y)
            pixels(index + 1) = CByte(Y)
            pixels(index + 0) = CByte(Y)
         Next
      Next
      'Copy the RGB values back to the bitmap
      System.Runtime.InteropServices.Marshal.Copy(pixels, 0, ptr, size)
      'Unlock the bits.
      result.UnlockBits(bmpData)
      Return result
   End Function

   ''' <summary>
   ''' Execute filter on (A)RGB image with 8 bits per color.
   ''' </summary>
   ''' <param name="img"></param>
   ''' <returns></returns>
   ''' <remarks></remarks>
   Public Function ExecuteRgb8Matrix( _
            ByVal img As System.Drawing.Image) As System.Drawing.Image
      'Reference from http://www.bobpowell.net/grayscale.htm
      Dim result As Bitmap = New Bitmap(img)
      result.SetResolution(img.HorizontalResolution, img.VerticalResolution)
      Dim g As Graphics = Graphics.FromImage(result)
      Dim colorMatrix As ColorMatrix
      If (_brightness) Then
         colorMatrix = New ColorMatrix(New Single()() _
                  { _
                     New Single() {0.5, 0.5, 0.5, 0, 0}, _
                     New Single() {0.5, 0.5, 0.5, 0, 0}, _
                     New Single() {0.5, 0.5, 0.5, 0, 0}, _
                     New Single() {0, 0, 0, 1, 0}, _
                     New Single() {0, 0, 0, 0, 1} _
                  })
      Else
         colorMatrix = New ColorMatrix(New Single()() _
                  { _
                     New Single() {0.3, 0.3, 0.3, 0, 0}, _
                     New Single() {0.59, 0.59, 0.59, 0, 0}, _
                     New Single() {0.11, 0.11, 0.11, 0, 0}, _
                     New Single() {0, 0, 0, 1, 0}, _
                     New Single() {0, 0, 0, 0, 1} _
                  })
      End If
      Dim imgAttributes As ImageAttributes = New ImageAttributes()
      imgAttributes.SetColorMatrix(colorMatrix)
      g.DrawImage(result, _
               New Rectangle(0, 0, img.Width, img.Height), _
               0, 0, img.Width, img.Height, _
               GraphicsUnit.Pixel, imgAttributes)
      g.Dispose()
      Return result
   End Function

End Class