CrossStitchCreator.ImagingTool.UpdateColourMapFrequency C# (CSharp) Method

        public void UpdateColourMapFrequency()
        {
            if (mOutput == null || ColourMap == null) return;
            ColourMap.ClearFrequencies();  // M
            Bitmap b = mOutput;
            for (int x = 0; x < b.Width; x++) // this loop iterates N times
                for (int y = 0; y < b.Height; y++)
                {
                    Color c = b.GetPixel(x, y);
                    ColourMap.Colours[c].Frequency++; // Dictionary access is log(M)?
                }
        }