//////////////////////////////////////////////////////////////////////////
// Main entry points for decompression
/// <summary>
/// Decompression initialization.
/// </summary>
/// <returns>Returns <c>false</c> if suspended. The return value need be inspected
/// only if a suspending data source is used.
/// </returns>
/// <remarks><see cref="jpeg_decompress_struct.jpeg_read_header">jpeg_read_header</see> must be completed before calling this.<br/>
///
/// If a multipass operating mode was selected, this will do all but the last pass, and thus may take a great deal of time.
/// </remarks>
/// <seealso cref="jpeg_decompress_struct.jpeg_finish_decompress"/>
/// <seealso href="9d052723-a7f9-42de-8747-0bd9896f8157.htm" target="_self">Decompression details</seealso>
public bool jpeg_start_decompress()
{
if (m_global_state == JpegState.DSTATE_READY)
{
/* First call: initialize master control, select active modules */
m_master = new jpeg_decomp_master(this);
if (m_buffered_image)
{
/* No more work here; expecting jpeg_start_output next */
m_global_state = JpegState.DSTATE_BUFIMAGE;
return true;
}
m_global_state = JpegState.DSTATE_PRELOAD;
}
if (m_global_state == JpegState.DSTATE_PRELOAD)
{
/* If file has multiple scans, absorb them all into the coef buffer */
if (m_inputctl.HasMultipleScans())
{
for ( ; ; )
{
ReadResult retcode;
/* Call progress monitor hook if present */
if (m_progress != null)
m_progress.Updated();
/* Absorb some more input */
retcode = m_inputctl.consume_input();
if (retcode == ReadResult.JPEG_SUSPENDED)
return false;
if (retcode == ReadResult.JPEG_REACHED_EOI)
break;
/* Advance progress counter if appropriate */
if (m_progress != null && (retcode == ReadResult.JPEG_ROW_COMPLETED || retcode == ReadResult.JPEG_REACHED_SOS))
{
m_progress.Pass_counter++;
if (m_progress.Pass_counter >= m_progress.Pass_limit)
{
/* underestimated number of scans; ratchet up one scan */
m_progress.Pass_limit += m_total_iMCU_rows;
}
}
}
}
m_output_scan_number = m_input_scan_number;
}
else if (m_global_state != JpegState.DSTATE_PRESCAN)
ERREXIT(J_MESSAGE_CODE.JERR_BAD_STATE, (int)m_global_state);
/* Perform any dummy output passes, and set up for the final pass */
return output_pass_setup();
}
