// Initialize the marker writer module.
static void jinit_marker_writer(jpeg_compress cinfo)
{
my_marker_writer marker=null;
try
{ // Create the subobject
marker=new my_marker_writer();
}
catch
{
ERREXIT1(cinfo, J_MESSAGE_CODE.JERR_OUT_OF_MEMORY, 4);
}
cinfo.marker=marker;
// Initialize method pointers
marker.write_file_header=write_file_header;
marker.write_frame_header=write_frame_header;
marker.write_scan_header=write_scan_header;
marker.write_file_trailer=write_file_trailer;
marker.write_tables_only=write_tables_only;
marker.write_marker_header=write_marker_header;
marker.write_marker_byte=write_marker_byte;
// Initialize private state
marker.last_restart_interval=0;
}
// Write scan header.
// This consists of DHT or DAC markers, optional DRI, and SOS.
// Compressed data will be written following the SOS.
static void write_scan_header(jpeg_compress cinfo)
{
if(cinfo.arith_code)
{
// Emit arith conditioning info. We may have some duplication
// if the file has multiple scans, but it's so small it's hardly
// worth worrying about.
emit_dac(cinfo);
}
else
{
// Emit Huffman tables.
// Note that emit_dht() suppresses any duplicate tables.
for(int i=0; i<cinfo.comps_in_scan; i++)
{
jpeg_component_info compptr=cinfo.cur_comp_info[i];
if(cinfo.process==J_CODEC_PROCESS.JPROC_PROGRESSIVE)
{
// Progressive mode: only DC or only AC tables are used in one scan
if(cinfo.Ss==0)
{
if(cinfo.Ah==0) emit_dht(cinfo, compptr.dc_tbl_no, false); // DC needs no table for refinement scan
}
else
{
emit_dht(cinfo, compptr.ac_tbl_no, true);
}
}
else if(cinfo.process==J_CODEC_PROCESS.JPROC_LOSSLESS)
{
// Lossless mode: only DC tables are used
emit_dht(cinfo, compptr.dc_tbl_no, false);
}
else
{
// Sequential mode: need both DC and AC tables
emit_dht(cinfo, compptr.dc_tbl_no, false);
emit_dht(cinfo, compptr.ac_tbl_no, true);
}
}
}
my_marker_writer marker=(my_marker_writer)cinfo.marker;
// Emit DRI if required --- note that DRI value could change for each scan.
// We avoid wasting space with unnecessary DRIs, however.
if(cinfo.restart_interval!=marker.last_restart_interval)
{
emit_dri(cinfo);
marker.last_restart_interval=cinfo.restart_interval;
}
emit_sos(cinfo);
}
// Write datastream header.
// This consists of an SOI and optional APPn markers.
// We recommend use of the JFIF marker, but not the Adobe marker,
// when using YCbCr or grayscale data. The JFIF marker should NOT
// be used for any other JPEG colorspace. The Adobe marker is helpful
// to distinguish RGB, CMYK, and YCCK colorspaces.
// Note that an application can write additional header markers after
// jpeg_start_compress returns.
static void write_file_header(jpeg_compress cinfo)
{
my_marker_writer marker=(my_marker_writer)cinfo.marker;
emit_marker(cinfo, JPEG_MARKER.M_SOI); // first the SOI
// SOI is defined to reset restart interval to 0
marker.last_restart_interval=0;
if(cinfo.write_JFIF_header) emit_jfif_app0(cinfo); // next an optional JFIF APP0
if(cinfo.exif!=null&&cinfo.exif.HasData) emit_exif_app1(cinfo); // next an optional EXIF APP1
if(cinfo.write_Adobe_marker) emit_adobe_app14(cinfo); // next an optional Adobe APP14
}
