画像のガンマ補正を行う方法

画像のガンマ補正を行う方法
VB.NET

Public Shared Function CreateGammaAdjustedImage(ByVal img As Image, _
        ByVal gammaValue As Single) As Image

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

    Dim g As Graphics = Graphics.FromImage(newImg)

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

    ia.SetGamma(1 / gammaValue)

    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 CreateGammaAdjustedImage(Image img, float gammaValue)
{

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

    Graphics g = Graphics.FromImage(newImg);

    System.Drawing.Imaging.ImageAttributes ia =
        new System.Drawing.Imaging.ImageAttributes();
 
    ia.SetGamma(1/gammaValue);

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

    g.Dispose();
    
    return newImg;
}