BitMiracle.LibJpeg.Classic.Internal.jpeg_downsampler.fullsize_smooth_downsample C# (CSharp) Method

        private void fullsize_smooth_downsample(int componentIndex, byte[][] input_data, int startInputRow, byte[][] output_data, int startOutRow)
        {
            /* Expand input data enough to let all the output samples be generated
             * by the standard loop.  Special-casing padded output would be more
             * efficient.
             */
            jpeg_component_info compptr = m_cinfo.Component_info[componentIndex];
            int output_cols = compptr.Width_in_blocks * compptr.DCT_h_scaled_size;
            expand_right_edge(input_data, startInputRow - 1, m_cinfo.m_max_v_samp_factor + 2, m_cinfo.m_image_width, output_cols);

            /* Each of the eight neighbor pixels contributes a fraction SF to the
             * smoothed pixel, while the main pixel contributes (1-8*SF).  In order
             * to use integer arithmetic, these factors are multiplied by 2^16 = 65536.
             * Also recall that SF = smoothing_factor / 1024.
             */

            int memberscale = 65536 - m_cinfo.m_smoothing_factor * 512; /* scaled 1-8*SF */
            int neighscale = m_cinfo.m_smoothing_factor * 64; /* scaled SF */

            for (int outrow = 0; outrow < m_cinfo.m_max_v_samp_factor; outrow++)
            {
                int outIndex = 0;
                int inIndex = 0;
                int aboveIndex = 0;
                int belowIndex = 0;

                /* Special case for first column */
                int colsum = input_data[startInputRow + outrow - 1][aboveIndex] +
                    input_data[startInputRow + outrow + 1][belowIndex] +
                    input_data[startInputRow + outrow][inIndex];

                aboveIndex++;
                belowIndex++;

                int membersum = input_data[startInputRow + outrow][inIndex];
                inIndex++;

                int nextcolsum = input_data[startInputRow + outrow - 1][aboveIndex] +
                    input_data[startInputRow + outrow + 1][belowIndex] +
                    input_data[startInputRow + outrow][inIndex];

                int neighsum = colsum + (colsum - membersum) + nextcolsum;

                membersum = membersum * memberscale + neighsum * neighscale;
                output_data[startOutRow + outrow][outIndex] = (byte)((membersum + 32768) >> 16);
                outIndex++;

                int lastcolsum = colsum;
                colsum = nextcolsum;

                for (int colctr = output_cols - 2; colctr > 0; colctr--)
                {
                    membersum = input_data[startInputRow + outrow][inIndex];

                    inIndex++;
                    aboveIndex++;
                    belowIndex++;

                    nextcolsum = input_data[startInputRow + outrow - 1][aboveIndex] +
                        input_data[startInputRow + outrow + 1][belowIndex] +
                        input_data[startInputRow + outrow][inIndex];

                    neighsum = lastcolsum + (colsum - membersum) + nextcolsum;
                    membersum = membersum * memberscale + neighsum * neighscale;

                    output_data[startOutRow + outrow][outIndex] = (byte)((membersum + 32768) >> 16);
                    outIndex++;

                    lastcolsum = colsum;
                    colsum = nextcolsum;
                }

                /* Special case for last column */
                membersum = input_data[startInputRow + outrow][inIndex];
                neighsum = lastcolsum + (colsum - membersum) + colsum;
                membersum = membersum * memberscale + neighsum * neighscale;
                output_data[startOutRow + outrow][outIndex] = (byte)((membersum + 32768) >> 16);
            }
        }