const int OUTPUT_BUF_SIZE = 4096; // choose an efficiently Write'able size
// Initialize destination --- called by jpeg_start_compress
// before any data is actually written.
static void init_destination(jpeg_compress cinfo)
{
my_destination_mgr dest = (my_destination_mgr)cinfo.dest;
// Allocate the output buffer --- it will be released when done with image
try
{
dest.buffer = new byte[OUTPUT_BUF_SIZE];
}
catch
{
ERREXIT1(cinfo, J_MESSAGE_CODE.JERR_OUT_OF_MEMORY, 4);
}
dest.output_bytes = dest.buffer;
dest.next_output_byte = 0;
dest.free_in_buffer = OUTPUT_BUF_SIZE;
}
// Terminate destination --- called by jpeg_finish_compress
// after all data has been written. Usually needs to flush buffer.
//
// NB: *not* called by jpeg_abort or jpeg_destroy; surrounding
// application must deal with any cleanup that should happen even
// for error exit.
static void term_destination(jpeg_compress cinfo)
{
my_destination_mgr dest = (my_destination_mgr)cinfo.dest;
int datacount = OUTPUT_BUF_SIZE - (int)dest.free_in_buffer;
// Write any data remaining in the buffer
if (datacount > 0)
{
try
{
dest.outfile.Write(dest.buffer, 0, datacount);
}
catch
{
ERREXIT(cinfo, J_MESSAGE_CODE.JERR_FILE_WRITE);
}
}
dest.outfile.Flush();
}
// Empty the output buffer --- called whenever buffer fills up.
//
// In typical applications, this should write the entire output buffer
// (ignoring the current state of next_output_byte & free_in_buffer),
// reset the pointer & count to the start of the buffer, and return true
// indicating that the buffer has been dumped.
//
// In applications that need to be able to suspend compression due to output
// overrun, a false return indicates that the buffer cannot be emptied now.
// In this situation, the compressor will return to its caller (possibly with
// an indication that it has not accepted all the supplied scanlines). The
// application should resume compression after it has made more room in the
// output buffer. Note that there are substantial restrictions on the use of
// suspension --- see the documentation.
//
// When suspending, the compressor will back up to a convenient restart point
// (typically the start of the current MCU). next_output_byte & free_in_buffer
// indicate where the restart point will be if the current call returns false.
// Data beyond this point will be regenerated after resumption, so do not
// write it out when emptying the buffer externally.
static bool empty_output_buffer(jpeg_compress cinfo)
{
my_destination_mgr dest = (my_destination_mgr)cinfo.dest;
try
{
dest.outfile.Write(dest.buffer, 0, OUTPUT_BUF_SIZE);
}
catch
{
ERREXIT(cinfo, J_MESSAGE_CODE.JERR_FILE_WRITE);
}
dest.output_bytes = dest.buffer;
dest.next_output_byte = 0;
dest.free_in_buffer = OUTPUT_BUF_SIZE;
return(true);
}
