Luminozitate

imi1 = pictureBox2.Image;
            ImUndo = imi1;
            Bitmap originalImage = new Bitmap(imi1.Width, imi1.Height);
            Graphics gi = Graphics.FromImage(originalImage);
            gi.DrawImage(imi1, 0, 0);
            Bitmap adjustedImage = originalImage;
            float brightness = 1.0f; // no change in brightness
            float contrast = Convert.ToSingle(numericUpDown1.Value); // twice the contrast
            float gamma = 1.0f; // no change in gamma

            float adjustedBrightness = brightness - 1.0f;
            // create matrix that will brighten and contrast the image
            float[][] ptsArray ={
            new float[] {contrast, 0, 0, 0, 0}, // scale red
            new float[] {0, contrast, 0, 0, 0}, // scale green
            new float[] {0, 0, contrast, 0, 0}, // scale blue
            new float[] {0, 0, 0, 1.0f, 0}, // don't scale alpha
            new float[] {adjustedBrightness, adjustedBrightness, adjustedBrightness, 0, 1}};
            System.Drawing.Imaging.ImageAttributes imageAttributes = new System.Drawing.Imaging.ImageAttributes();
            imageAttributes.ClearColorMatrix();
            imageAttributes.SetColorMatrix(new ColorMatrix(ptsArray), ColorMatrixFlag.Default, ColorAdjustType.Bitmap);
            imageAttributes.SetGamma(gamma, ColorAdjustType.Bitmap);
            Graphics g = Graphics.FromImage(adjustedImage);
            g.DrawImage(originalImage, new Rectangle(0, 0, adjustedImage.Width, adjustedImage.Height)
                , 0, 0, originalImage.Width, originalImage.Height,
                GraphicsUnit.Pixel, imageAttributes);
            pictureBox2.Image = adjustedImage;