画像の彩度を変更する方法

画像の彩度を変更する方法
VB.NET

Public Shared Function ChangeSaturation(ByVal img As Image, _
        ByVal saturation As Single) As Image

    Dim newImg As New Bitmap(img.Width, img.Height)

    Dim g As Graphics = Graphics.FromImage(newImg)

    Dim cm As New System.Drawing.Imaging.ColorMatrix()
    Const rwgt As Single = 0.3086F
    Const gwgt As Single = 0.6094F
    Const bwgt As Single = 0.082F
    cm.Matrix01 = (1.0F - saturation) * rwgt
    cm.Matrix02 = cm.Matrix01
    cm.Matrix00 = cm.Matrix01 + saturation
    cm.Matrix10 = (1.0F - saturation) * gwgt
    cm.Matrix12 = cm.Matrix10
    cm.Matrix11 = cm.Matrix10 + saturation
    cm.Matrix20 = (1.0F - saturation) * bwgt
    cm.Matrix21 = cm.Matrix20
    cm.Matrix22 = cm.Matrix20 + saturation
    cm.Matrix33 = 1
    cm.Matrix44 = 1

    Dim ia As New System.Drawing.Imaging.ImageAttributes()

    ia.SetColorMatrix(cm)

    g.DrawImage(img, New Rectangle(0, 0, img.Width, img.Height), _
                0, 0, img.Width, img.Height, GraphicsUnit.Pixel, ia)

    g.Dispose()

    Return newImg
End Function

C#

public static Image ChangeSaturation(Image img, float saturation)
{

    Bitmap newImg = new Bitmap(img.Width, img.Height);

    Graphics g = Graphics.FromImage(newImg);

    System.Drawing.Imaging.ColorMatrix cm =
        new System.Drawing.Imaging.ColorMatrix();
    const float rwgt = 0.3086f;
    const float gwgt = 0.6094f;
    const float bwgt = 0.0820f;
    cm.Matrix01 = cm.Matrix02 = (1f - saturation) * rwgt;
    cm.Matrix00 = cm.Matrix01 + saturation;
    cm.Matrix10 = cm.Matrix12 = (1f - saturation) * gwgt;
    cm.Matrix11 = cm.Matrix10 + saturation;
    cm.Matrix20 = cm.Matrix21 = (1f - saturation) * bwgt;
    cm.Matrix22 = cm.Matrix20 + saturation;
    cm.Matrix33 = cm.Matrix44 = 1;

    System.Drawing.Imaging.ImageAttributes ia =
        new System.Drawing.Imaging.ImageAttributes();

    ia.SetColorMatrix(cm);

    g.DrawImage(img,
        new Rectangle(0, 0, img.Width, img.Height),
        0, 0, img.Width, img.Height, GraphicsUnit.Pixel, ia);

    g.Dispose();

    return newImg;
}