private static System.Drawing.Image GrayScale(ref System.Drawing.Image source)
{
    Bitmap bitMap = new Bitmap(source);

    using (Graphics g = Graphics.FromImage(bitMap))
    {
        System.Drawing.Imaging.ColorMatrix matrix = new System.Drawing.Imaging.ColorMatrix(
            new float[][]
            {
                new float[] {.3f, .3f, .3f, 0, 0},
                new float[] {.59f, .59f, .59f, 0, 0},
                new float[] {.11f, .11f, .11f, 0, 0},
                new float[] {0, 0, 0, 1, 0},
                new float[] {0, 0, 0, 0, 1}
            });

        System.Drawing.Imaging.ImageAttributes attributes = new System.Drawing.Imaging.ImageAttributes();
        attributes.SetColorMatrix(matrix);

        g.DrawImage(source, new Rectangle(0, 0, source.Width, source.Height), 0, 0, source.Width, source.Height, GraphicsUnit.Pixel, attributes);
    }

    return (System.Drawing.Image)bitMap;
}

Posted: March 18, 2023

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