BitMiracle.LibJpeg.Classic.Internal.my_2pass_cquantizer.start_pass C# (CSharp) Method

        public virtual void start_pass(bool is_pre_scan)
        {
            /* Only F-S dithering or no dithering is supported. */
            /* If user asks for ordered dither, give him F-S. */
            if (m_cinfo.m_dither_mode != J_DITHER_MODE.JDITHER_NONE)
                m_cinfo.m_dither_mode = J_DITHER_MODE.JDITHER_FS;

            if (is_pre_scan)
            {
                /* Set up method pointers */
                m_quantizer = QuantizerType.prescan_quantizer;
                m_useFinishPass1 = true;
                m_needs_zeroed = true; /* Always zero histogram */
            }
            else
            {
                /* Set up method pointers */
                if (m_cinfo.m_dither_mode == J_DITHER_MODE.JDITHER_FS)
                    m_quantizer = QuantizerType.pass2_fs_dither_quantizer;
                else
                    m_quantizer = QuantizerType.pass2_no_dither_quantizer;

                m_useFinishPass1 = false;

                /* Make sure color count is acceptable */
                int i = m_cinfo.m_actual_number_of_colors;
                if (i < 1)
                    m_cinfo.ERREXIT(J_MESSAGE_CODE.JERR_QUANT_FEW_COLORS, 1);

                if (i > MAXNUMCOLORS)
                    m_cinfo.ERREXIT(J_MESSAGE_CODE.JERR_QUANT_MANY_COLORS, MAXNUMCOLORS);

                if (m_cinfo.m_dither_mode == J_DITHER_MODE.JDITHER_FS)
                {
                    /* Allocate Floyd-Steinberg workspace if we didn't already. */
                    if (m_fserrors == null)
                    {
                        int arraysize = (m_cinfo.m_output_width + 2) * 3;
                        m_fserrors = new short[arraysize];
                    }
                    else
                    {
                        /* Initialize the propagated errors to zero. */
                        Array.Clear(m_fserrors, 0, m_fserrors.Length);
                    }

                    /* Make the error-limit table if we didn't already. */
                    if (m_error_limiter == null)
                        init_error_limit();

                    m_on_odd_row = false;
                }
            }

            /* Zero the histogram or inverse color map, if necessary */
            if (m_needs_zeroed)
            {
                for (int i = 0; i < HIST_C0_ELEMS; i++)
                    Array.Clear(m_histogram[i], 0, m_histogram[i].Length);

                m_needs_zeroed = false;
            }
        }