ImageBox.show() by Accord.Controls;

        private void button7_Click(object sender, EventArgs e)
        {
            Bitmap img1 = (Bitmap)pictureBox1.Image;
            // create filter
            Accord.Imaging.Filters.HistogramEqualization filter =
                new Accord.Imaging.Filters.HistogramEqualization();
            // process image
            filter.ApplyInPlace(img1);

            //pictureBox2.Image = img1;

            ImageBox.Show(img1);
        }