private void rgb_gray_convert(ComponentBuffer[] input_buf, int input_row, byte[][] output_buf, int output_row, int num_rows)
{
int component0RowOffset = m_perComponentOffsets[0];
int component1RowOffset = m_perComponentOffsets[1];
int component2RowOffset = m_perComponentOffsets[2];
int num_cols = m_cinfo.m_output_width;
for (int row = 0; row < num_rows; row++)
{
int columnOffset = 0;
for (int col = 0; col < num_cols; col++)
{
int r = input_buf[0][input_row + component0RowOffset][col];
int g = input_buf[1][input_row + component1RowOffset][col];
int b = input_buf[2][input_row + component2RowOffset][col];
/* Y */
output_buf[output_row + row][columnOffset++] = (byte)((rgb_y_tab[r + R_Y_OFF] + rgb_y_tab[g + G_Y_OFF] + rgb_y_tab[b + B_Y_OFF]) >> SCALEBITS);
}
}
}