winform对图片进行灰度处理

        //图片进行灰度处理
        //originalImage为原图像   返回灰度图像
        private Bitmap GrayImage(Bitmap originalImage)
        {
            ImageAttributes imageAttributes = new ImageAttributes();
            float[][] matrix = { new float[] {0.299f, 0.299f, 0.299f, 0, 0},
                                             new float[]   {0.587f,   0.587f,   0.587f,   0,   0}, 
                                             new float[]   {0.114f,   0.114f,   0.114f,   0,   0},
                                             new float[]   {0,   0,   0,   1,   0},                   
                                             new float[]   {0,   0,   0,   0,   1}
                                   };
            ColorMatrix colorMatrix = new ColorMatrix(matrix);
            imageAttributes.SetColorMatrix(colorMatrix, ColorMatrixFlag.Default, ColorAdjustType.Bitmap);

            Bitmap grayHead = new Bitmap(originalImage.Width, originalImage.Height);
            using (Graphics g = Graphics.FromImage(grayHead))
            {
                g.DrawImage(originalImage, new Rectangle(0, 0, originalImage.Width, originalImage.Height), 0, 0, originalImage.Width, originalImage.Height, GraphicsUnit.Pixel, imageAttributes);
            }
            return grayHead;
        }