Removing non red toned pixels

I have a very simple image processing application.

I am trying to remove the pixels which do not involve red tones.

So far a basic code seems to achieve what I want.

        private void removeUnRedCellsBtn_Click(object sender, EventArgs e)
        {
            byte threshold = Convert.ToByte(diffTxtBox.Text); 
            byte r, g, b;
            for (int i = 0; i < m_Bitmap.Width; i++)
            {
                for (int j = 0; j < m_Bitmap.Height; j++)
                {
                    r = im_matrix[i, j].R;
                    g = im_matrix[i, j].G;
                    b = im_matrix[i, j].B;
                    if ((r - b) < threshold || (r - g) < threshold)
                    {
                        m_Bitmap.SetPixel(i, j, Color.White);
                    }

                }
            }
            pictureArea_PictureBox.Image = m_Bitmap;
        }

Basically if the difference of (red and blue) or (red and green) is less than a threshold it sets the pixel to white.

My results seems to be promising however I 开发者_如何学Pythonam wondering if there is a better solution for determining whether a pixel involves red tones in it.

My results for a threshold value of 75 is

Any algorithm or thought will be very appreciated.

Thanks in advance

You might have more luck if you convert the RGB values to a different color space, like HSL or HSV. Check out this link on Wikipedia. Converting a pixel to one of those color spaces should help you isolate the hue, which is what you're mostly concerned with.