public software.sextractor

/*

*                               scan.c

*

* Main image scanning routines.

*

*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

*

*       This file part of:      SExtractor

*

*       Copyright:              (C) 1993-2010 Emmanuel Bertin -- IAP/CNRS/UPMC

*

*       License:                GNU General Public License

*

*       SExtractor is free software: you can redistribute it and/or modify

*       it under the terms of the GNU General Public License as published by

*       the Free Software Foundation, either version 3 of the License, or

*       (at your option) any later version.

*       SExtractor is distributed in the hope that it will be useful,

*       but WITHOUT ANY WARRANTY; without even the implied warranty of

*       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

*       GNU General Public License for more details.

*       You should have received a copy of the GNU General Public License

*       along with SExtractor. If not, see <http://www.gnu.org/licenses/>.

*

*       Last modified:          11/10/2010

*

*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/

#ifdef HAVE_CONFIG_H

#include        "config.h"

#endif

#include        <math.h>

#include        <stdio.h>

#include        <stdlib.h>

#include        <string.h>

#include        "define.h"

#include        "globals.h"

#include        "prefs.h"

#include        "back.h"

#include        "check.h"

#include        "clean.h"

#include        "extract.h"

#include        "filter.h"

#include        "image.h"

#include        "plist.h"

#include        "weight.h"

/****************************** scanimage ************************************

PROTO   void scanimage(picstruct *field, picstruct *dfield, picstruct *ffield,

        picstruct *wfield, picstruct *dwfield)

PURPOSE Scan of the large pixmap(s). Main loop and heart of the program.

INPUT   Measurement field pointer,

        Detection field pointer,

        Flag field pointer,

        Measurement weight-map field pointer,

        Detection weight-map field pointer,

OUTPUT  -.

NOTES   -.

AUTHOR  E. Bertin (IAP)

VERSION 28/09/2010

 ***/

void    scanimage(picstruct *field, picstruct *dfield, picstruct **pffield,

                int nffield, picstruct *wfield, picstruct *dwfield)

  {

   static infostruct    curpixinfo, *info, *store,

                        initinfo, freeinfo, *victim;

   picstruct            *ffield;

   checkstruct          *check;

   objliststruct        objlist;

   objstruct            *cleanobj;

   pliststruct          *pixel, *pixt;

   picstruct            *cfield, *cdwfield;

   char                 *marker, newmarker, *blankpad, *bpt,*bpt0;

   int                  co, i,j, flag, luflag,pstop, xl,xl2,yl, cn,

                        nposize, stacksize, w, h, blankh, maxpixnb,

                        varthreshflag, ontotal;

   short                trunflag;

   PIXTYPE              thresh, relthresh, cdnewsymbol, cdvar,cdwthresh,wthresh,

                        *scan,*dscan,*cdscan,*dwscan,*dwscanp,*dwscann,

                        *cdwscan,*cdwscanp,*cdwscann,*wscand,

                        *scant, *wscan,*wscann,*wscanp;

   FLAGTYPE             *pfscan[MAXFLAG];

   status               cs, ps, *psstack;

   int                  *start, *end, ymax;

/* Avoid gcc -Wall warnings */

  scan = dscan = cdscan = cdwscan = cdwscann = cdwscanp

        = dwscan = dwscann = dwscanp

        = wscan = wscann = wscanp = NULL;

  victim = NULL;                        /* Avoid gcc -Wall warnings */

  blankh = 0;                            /* Avoid gcc -Wall warnings */

/*----- Beginning of the main loop: Initialisations  */

  thecat.ntotal = thecat.ndetect = 0;

/* cfield is the detection field in any case */

  cfield = dfield? dfield:field;

/* cdwfield is the detection weight-field if available */

  cdwfield = dwfield? dwfield:(prefs.dweight_flag?wfield:NULL);

  cdwthresh = cdwfield ? cdwfield->weight_thresh : 0.0;

  if (cdwthresh>BIG*WTHRESH_CONVFAC);

    cdwthresh = BIG*WTHRESH_CONVFAC;

  wthresh = wfield? wfield->weight_thresh : 0.0;

/* If WEIGHTing and no absolute thresholding, activate threshold scaling */

  varthreshflag = (cdwfield && prefs.thresh_type[0]!=THRESH_ABSOLUTE);

  relthresh = varthreshflag ? prefs.dthresh[0] : 0.0;/* To avoid gcc warnings*/

  w = cfield->width;

  h = cfield->height;

  objlist.dthresh = cfield->dthresh;

  objlist.thresh = field->thresh;

  cfield->yblank = 1;

  field->y = field->stripy = 0;

  field->ymin = field->stripylim = 0;

  field->stripysclim = 0;

  if (dfield)

    {

    dfield->y = dfield->stripy = 0;

    dfield->ymin = dfield->stripylim = 0;

    dfield->stripysclim = 0;

    }

  if (nffield)

    for (i=0; i<nffield; i++)

      {

      ffield = pffield[i];

      ffield->y = ffield->stripy = 0;

      ffield->ymin = ffield->stripylim = 0;

      ffield->stripysclim = 0;

      }

  if (wfield)

    {

    wfield->y = wfield->stripy = 0;

    wfield->ymin = wfield->stripylim = 0;

    wfield->stripysclim = 0;

    }

  if (dwfield)

    {

    dwfield->y = dwfield->stripy = 0;

    dwfield->ymin = dwfield->stripylim = 0;

    dwfield->stripysclim = 0;

    }

/*Allocate memory for buffers */

  stacksize = w+1;

  QMALLOC(info, infostruct, stacksize);

  QCALLOC(store, infostruct, stacksize);

  QMALLOC(marker, char, stacksize);

  QMALLOC(dumscan, PIXTYPE, stacksize);

  QMALLOC(psstack, status, stacksize);

  QCALLOC(start, int, stacksize);

  QMALLOC(end, int, stacksize);

  blankpad = bpt = NULL;

  lutzalloc(w,h);

  allocparcelout();

/* Some initializations */

  thresh = objlist.dthresh;

  initinfo.pixnb = 0;

  initinfo.flag = 0;

  initinfo.firstpix = initinfo.lastpix = -1;

  for (xl=0; xl<stacksize; xl++)

    {

    marker[xl]  = 0 ;

    dumscan[xl] = -BIG ;

    }

  co = pstop = 0;

  objlist.nobj = 1;

  curpixinfo.pixnb = 1;

/* Init cleaning procedure */

  initclean();

/*----- Allocate memory for the pixel list */

  init_plist();

  if (!(pixel = objlist.plist = malloc(nposize=prefs.mem_pixstack*plistsize)))

    error(EXIT_FAILURE, "Not enough memory to store the pixel stack:\n",

        "           Try to decrease MEMORY_PIXSTACK");

/*----- at the beginning, "free" object fills the whole pixel list */

  freeinfo.firstpix = 0;

  freeinfo.lastpix = nposize-plistsize;

  pixt = pixel;

  for (i=plistsize; i<nposize; i += plistsize, pixt += plistsize)

    PLIST(pixt, nextpix) = i;

  PLIST(pixt, nextpix) = -1;

/* Allocate memory for other buffers */

  if (prefs.filter_flag)

    {

    QMALLOC(cdscan, PIXTYPE, stacksize);

    if (cdwfield)

      {

      QCALLOC(cdwscan, PIXTYPE, stacksize);

      if (PLISTEXIST(wflag))

        {

        QCALLOC(cdwscanp, PIXTYPE, stacksize);

        QCALLOC(cdwscann, PIXTYPE, stacksize);

        }

      }

/*-- One needs a buffer to protect filtering if source-blanking applies */

    if (prefs.blank_flag)

      {

      blankh = thefilter->convh/2+1;

      QMALLOC(blankpad, char, w*blankh);

      cfield->yblank -= blankh;

      if (dfield)

        field->yblank = cfield->yblank;

      bpt = blankpad;

      }

    }

/*----- Here we go */

  for (yl=0; yl<=h;)

    {

    ps = COMPLETE;

    cs = NONOBJECT;

    if (yl==h)

      {

/*---- Need an empty line for Lutz' algorithm to end gracely */

      if (prefs.filter_flag)

        {

        free(cdscan);

        if (cdwfield)

          {

          if (PLISTEXIST(wflag))

            {

            free(cdwscanp);

            free(cdwscann);

            cdwscanp = cdwscan;

            }

          else

            free(cdwscan);

          }

        }

      cdwscan = cdwscann = cdscan = dumscan;

      }

    else

      {

      if (nffield)

        for (i=0; i<nffield; i++)

          {

          ffield = pffield[i];

          pfscan[i] = (ffield->stripy==ffield->stripysclim)?

                  (FLAGTYPE *)loadstrip(ffield, (picstruct *)NULL)

                : &ffield->fstrip[ffield->stripy*ffield->width];

          }

      if (wfield)

        {

/*------ Copy the previous weight line to track bad pixel limits */

        wscan = (wfield->stripy==wfield->stripysclim)?

                  (PIXTYPE *)loadstrip(wfield, (picstruct *)NULL)

                : &wfield->strip[wfield->stripy*wfield->width];

        if (PLISTEXIST(wflag))

          {

          if (yl>0)

            wscanp = &wfield->strip[((yl-1)%wfield->stripheight)*wfield->width];

          if (yl<h-1)

            wscann = &wfield->strip[((yl+1)%wfield->stripheight)*wfield->width];

          }

        }

      scan = (field->stripy==field->stripysclim)?

                  (PIXTYPE *)loadstrip(field, wfield)

                : &field->strip[field->stripy*field->width];

      if (dwfield)

        {

        dwscan = (dwfield->stripy==dwfield->stripysclim)?

                  (PIXTYPE *)loadstrip(dwfield,

                                dfield?(picstruct *)NULL:dwfield)

                : &dwfield->strip[dwfield->stripy*dwfield->width];

        if (PLISTEXIST(wflag))

          {

          if (yl>0)

            dwscanp = &dwfield->strip[((yl-1)%dwfield->stripheight)

                        *dwfield->width];

          if (yl<h-1)

            dwscann = &dwfield->strip[((yl+1)%dwfield->stripheight)

                        *dwfield->width];

          }

        }

      else

        {

        dwscan = wscan;

        if (PLISTEXIST(wflag))

          {

          dwscanp = wscanp;

          dwscann = wscann;

          }

        }

      if (dfield)

        dscan = (dfield->stripy==dfield->stripysclim)?

                  (PIXTYPE *)loadstrip(dfield, dwfield)

                : &dfield->strip[dfield->stripy*dfield->width];

      else

        dscan = scan;

      if (prefs.filter_flag)

        {

        filter(cfield, cdscan, cfield->y);

        if (cdwfield)

          {

          if (PLISTEXIST(wflag))

            {

            if (yl==0)

              filter(cdwfield, cdwscann, yl);

            wscand = cdwscanp;

            cdwscanp = cdwscan;

            cdwscan = cdwscann;

            cdwscann = wscand;

            if (yl < h-1)

              filter(cdwfield, cdwscann, yl + 1);

            }

          else

            filter(cdwfield, cdwscan, yl);

          }

        }

      else

        {

        cdscan = dscan;

        cdwscan = dwscan;

        if (PLISTEXIST(wflag))

          {

          cdwscanp = dwscanp;

          cdwscann = dwscann;

          }

        }

      if ((check=prefs.check[CHECK_FILTERED]))

        writecheck(check, cdscan, w);

      }

    trunflag = (yl==0 || yl==h-1)? OBJ_TRUNC:0;

    for (xl=0; xl<=w; xl++)

      {

      if (xl == w)

        cdnewsymbol = -BIG;

      else

        cdnewsymbol = cdscan[xl];

      newmarker = marker[xl];

      marker[xl] = 0;

      curpixinfo.flag = trunflag;

      if (varthreshflag)

        thresh = relthresh*sqrt(cdvar = ((xl==w || yl==h)? 0.0:cdwscan[xl]));

      luflag = cdnewsymbol > thresh?1:0;

      if (luflag)

        {

        if (xl==0 || xl==w-1)

          curpixinfo.flag |= OBJ_TRUNC;

        pixt = pixel + (cn=freeinfo.firstpix);

        freeinfo.firstpix = PLIST(pixt, nextpix);

/*------- Running out of pixels, the largest object becomes a "victim" ------*/

        if (freeinfo.firstpix==freeinfo.lastpix)

          {

          sprintf(gstr, "%d,%d", xl+1, yl+1);

          warning("Pixel stack overflow at position ", gstr);

          maxpixnb = 0;

          for (i=0; i<=w; i++)

            if (store[i].pixnb>maxpixnb)

              if (marker[i]=='S' || (newmarker=='S' && i==xl))

                {

                flag = 0;

                if (i<xl)

                  for (j=0; j<=co; j++)

                    flag |= (start[j]==i);

                if (!flag)

                  maxpixnb = (victim = &store[i])->pixnb;

                }

          for (j=1; j<=co; j++)

            if (info[j].pixnb>maxpixnb)

              maxpixnb = (victim = &info[j])->pixnb;

          if (!maxpixnb)

            error(EXIT_FAILURE, "*Fatal Error*: something is badly bugged in ",

                "scanimage()!");

          if (maxpixnb <= 1)

            error(EXIT_FAILURE, "Pixel stack overflow in ", "scanimage()");

          freeinfo.firstpix = PLIST(pixel+victim->firstpix, nextpix);

          PLIST(pixel+victim->lastpix, nextpix) = freeinfo.lastpix;

          PLIST(pixel+(victim->lastpix=victim->firstpix), nextpix) = -1;

          victim->pixnb = 1;

          victim->flag |= OBJ_OVERFLOW;

          }

/*---------------------------------------------------------------------------*/

        curpixinfo.lastpix = curpixinfo.firstpix = cn;

        PLIST(pixt, nextpix) = -1;

        PLIST(pixt, x) = xl;

        PLIST(pixt, y) = yl;

        PLIST(pixt, value) = scan[xl];

        if (PLISTEXIST(dvalue))

          PLISTPIX(pixt, dvalue) = dscan[xl];

        if (PLISTEXIST(cdvalue))

          PLISTPIX(pixt, cdvalue) = cdnewsymbol;

        if (PLISTEXIST(flag))

          for (i=0; i<nffield; i++)

            PLISTFLAG(pixt, flag[i]) = pfscan[i][xl];

/*--------------------- Detect pixels with a low weight ---------------------*/

        if (PLISTEXIST(wflag) && wscan)

          {

          PLISTFLAG(pixt, wflag) = 0;

          if (wscan[xl] >= wthresh)

            PLISTFLAG(pixt, wflag) |= OBJ_LOWWEIGHT;

          if (cdwscan[xl] >= cdwthresh)

            PLISTFLAG(pixt, wflag) |= OBJ_LOWDWEIGHT;

          if (yl>0)

            {

            if (cdwscanp[xl] >= cdwthresh)

              PLISTFLAG(pixt, wflag) |= OBJ_LOWDWEIGHT;

            if (xl>0 && cdwscanp[xl-1]>=cdwthresh)

              PLISTFLAG(pixt, wflag) |= OBJ_LOWDWEIGHT;

            if (xl<w-1 && cdwscanp[xl+1]>=cdwthresh)

              PLISTFLAG(pixt, wflag) |= OBJ_LOWDWEIGHT;

            }

          if (xl>0 && cdwscan[xl-1]>=cdwthresh)

              PLISTFLAG(pixt, wflag) |= OBJ_LOWDWEIGHT;

          if (xl<w-1 && cdwscan[xl+1]>=cdwthresh)

            PLISTFLAG(pixt, wflag) |= OBJ_LOWDWEIGHT;

          if (yl<h-1)

            {

            if (cdwscann[xl] >= cdwthresh)

              PLISTFLAG(pixt, wflag) |= OBJ_LOWDWEIGHT;

            if (xl>0 && cdwscann[xl-1]>=cdwthresh)

              PLISTFLAG(pixt, wflag) |= OBJ_LOWDWEIGHT;

            if (xl<w-1 && cdwscann[xl+1]>=cdwthresh)

              PLISTFLAG(pixt, wflag) |= OBJ_LOWDWEIGHT;

            }

          }

        if (PLISTEXIST(dthresh))

          PLISTPIX(pixt, dthresh) = thresh;

        if (PLISTEXIST(var))

          PLISTPIX(pixt, var) = wscan[xl];

        if (cs != OBJECT)

/*------------------------------- Start Segment -----------------------------*/

          {

          cs = OBJECT;

          if (ps == OBJECT)

            {

            if (start[co] == UNKNOWN)

              {

              marker[xl] = 'S';

              start[co] = xl;

              }

            else

              marker[xl] = 's';

            }

          else

            {

            psstack[pstop++] = ps;

            marker[xl] = 'S';

            start[++co] = xl;

            ps = COMPLETE;

            info[co] = initinfo;

            }

          }

/*---------------------------------------------------------------------------*/

        }

      if (newmarker)

/*---------------------------- Process New Marker ---------------------------*/

        {

        if (newmarker == 'S')

          {

          psstack[pstop++] = ps;

          if (cs == NONOBJECT)

            {

            psstack[pstop++] = COMPLETE;

            info[++co] = store[xl];

            start[co] = UNKNOWN;

            }

          else

            update (&info[co],&store[xl], pixel);

          ps = OBJECT;

          }

        else if (newmarker == 's')

          {

          if ((cs == OBJECT) && (ps == COMPLETE))

            {

            pstop--;

            xl2 = start[co];

            update (&info[co-1],&info[co], pixel);

            if (start[--co] == UNKNOWN)

              start[co] = xl2;

            else

              marker[xl2] = 's';

            }

          ps = OBJECT;

          }

        else if (newmarker == 'f')

          ps = INCOMPLETE;

        else if (newmarker == 'F')

          {

          ps = psstack[--pstop];

          if ((cs == NONOBJECT) && (ps == COMPLETE))

            {

            if (start[co] == UNKNOWN)

              {

              if ((int)info[co].pixnb >= prefs.ext_minarea)

                {

                sortit(field, dfield, wfield, cdwfield, &info[co], &objlist,

                       cdwscan, wscan);

                }

/* ------------------------------------ free the chain-list */

              PLIST(pixel+info[co].lastpix, nextpix) = freeinfo.firstpix;

              freeinfo.firstpix = info[co].firstpix;

              }

            else

              {

              marker[end[co]] = 'F';

              store[start[co]] = info[co];

              }

            co--;

            ps = psstack[--pstop];

            }

          }

        }

/*---------------------------------------------------------------------------*/

      if (luflag)

        update (&info[co],&curpixinfo, pixel);

      else

        {

        if (cs == OBJECT)

/*-------------------------------- End Segment ------------------------------*/

          {

          cs = NONOBJECT;

          if (ps != COMPLETE)

            {

            marker[xl] = 'f';

            end[co] = xl;

            }

          else

            {

            ps = psstack[--pstop];

            marker[xl] = 'F';

            store[start[co]] = info[co];

            co--;

            }

          }

        }

      if (prefs.blank_flag && xl<w)

        {

        if (prefs.filter_flag)

          *(bpt++) = (luflag)?1:0;

        else if (luflag)

          dscan[xl] = -BIG;

        if (dfield && luflag)

          scan[xl] = -BIG;

        }

/*--------------------- End of the loop over the x's -----------------------*/

      }

/* Detected pixel removal at the end of each line */

    if (prefs.blank_flag && yl<h)

      {

      if (prefs.filter_flag)

        {

        bpt = bpt0 = blankpad + w*((yl+1)%blankh);

        if (cfield->yblank >= 0)

          {

          scant = &PIX(cfield, 0, cfield->yblank);

          for (i=w; i--; scant++)

            if (*(bpt++))

              *scant = -BIG;

          if (dfield)

            {

            bpt = bpt0;

            scant = &PIX(field, 0, cfield->yblank);

            for (i=w; i--; scant++)

              if (*(bpt++))

                *scant = -BIG;

            }

          bpt = bpt0;

          }

        }

      cfield->yblank++;

      if (dfield)

        field->yblank = cfield->yblank;

      }

/*-- Prepare markers for the next line */

    yl++;

    field->stripy = (field->y=yl)%field->stripheight;

    if (dfield)

      dfield->stripy = (dfield->y=yl)%dfield->stripheight;

    if (nffield)

      for (i=0; i<nffield; i++)

        {

        ffield = pffield[i];

        ffield->stripy = (ffield->y=yl)%ffield->stripheight;

        }

    if (wfield)

      wfield->stripy = (wfield->y=yl)%wfield->stripheight;

    if (dwfield)

      dwfield->stripy = (dwfield->y=yl)%dwfield->stripheight;

/*-- Remove objects close to the ymin limit if ymin is ready to increase */

    if (cfield->stripy==cfield->stripysclim)

      {

      cleanobj = cleanobjlist->obj+cleanobjlist->nobj-1;

      ontotal = 0;

      for (i=cleanobjlist->nobj; i--; cleanobj--)

        {

        if (cleanobj->ycmin <= cfield->ymin)

          {

/*-------- Warn if there is a possibility for any aperture to be truncated */

          if ((ymax=cleanobj->ycmax) > cfield->ymax)

            {

            sprintf(gstr, "Object at position %.0f,%.0f ",

                cleanobj->mx+1, cleanobj->my+1);

            QWARNING(gstr, "may have some apertures truncated:\n"

                "          You might want to increase MEMORY_BUFSIZE");

            }

          else if (ymax>cfield->yblank && prefs.blank_flag)

            {

            sprintf(gstr, "Object at position %.0f,%.0f ",

                cleanobj->mx+1, cleanobj->my+1);

            QWARNING(gstr, "may have some unBLANKed neighbours:\n"

                "          You might want to increase MEMORY_PIXSTACK");

            }

          if ((prefs.prof_flag && !(thecat.ntotal%10)

                && thecat.ntotal != ontotal)

                || !(thecat.ntotal%400))

            NPRINTF(OUTPUT, "\33[1M> Line:%5d  "

                "Objects: %8d detected / %8d sextracted\n\33[1A",

                yl>h? h:yl, thecat.ndetect, thecat.ntotal);

          ontotal = thecat.ntotal;

          endobject(field, dfield, wfield, cdwfield, i, cleanobjlist);

          subcleanobj(i);

          cleanobj = cleanobjlist->obj+i;       /* realloc in subcleanobj() */

          }

        }

      }

    if ((prefs.prof_flag && !(thecat.ntotal%10)) || !(yl%25))

      NPRINTF(OUTPUT, "\33[1M> Line:%5d  "

                "Objects: %8d detected / %8d sextracted\n\33[1A",

        yl>h?h:yl, thecat.ndetect, thecat.ntotal);

/*--------------------- End of the loop over the y's -----------------------*/

    }

/* Removal or the remaining pixels */

  if (prefs.blank_flag && prefs.filter_flag && (cfield->yblank >= 0))

    for (j=blankh-1; j--; yl++)

      {

      bpt = bpt0 = blankpad + w*(yl%blankh);

      scant = &PIX(cfield, 0, cfield->yblank);

      for (i=w; i--; scant++)

        if (*(bpt++))

          *scant = -BIG;

      if (dfield)

        {

        bpt = bpt0;

        scant = &PIX(field, 0, cfield->yblank);

        for (i=w; i--; scant++)

          if (*(bpt++))

            *scant = -BIG;

        }

      cfield->yblank++;

      if (dfield)

        field->yblank = cfield->yblank;

      }

/* Now that all "detected" pixels have been removed, analyse detections */

  ontotal = 0;

  for (j=cleanobjlist->nobj; j--;)

    {

    if ((prefs.prof_flag && !(thecat.ntotal%10) && thecat.ntotal != ontotal)

                || !(thecat.ntotal%400))

      NPRINTF(OUTPUT, "\33[1M> Line:%5d  "

                "Objects: %8d detected / %8d sextracted\n\33[1A",

        h, thecat.ndetect, thecat.ntotal);

    ontotal = thecat.ntotal;

    endobject(field, dfield, wfield, cdwfield, 0, cleanobjlist);

    subcleanobj(0);

    }

  endclean();

/*Free memory */

  if (prefs.filter_flag && cdwfield && PLISTEXIST(wflag))

    free(cdwscanp);

  freeparcelout();

  free(pixel);

  lutzfree();

  free(info);

  free(store);

  free(marker);

  free(dumscan);

  free(psstack);

  free(start);

  free(end);

  if (prefs.blank_flag && prefs.filter_flag)

    free(blankpad);

  return;

  }

/********************************* update ************************************/

/*

update object's properties each time one of its pixels is scanned by lutz()

*/

void  update(infostruct *infoptr1, infostruct *infoptr2, pliststruct *pixel)

  {

  infoptr1->pixnb += infoptr2->pixnb;

  infoptr1->flag |= infoptr2->flag;

  if (infoptr1->firstpix == -1)

    {

    infoptr1->firstpix = infoptr2->firstpix;

    infoptr1->lastpix = infoptr2->lastpix;

    }

  else if (infoptr2->lastpix != -1)

    {

    PLIST(pixel+infoptr1->lastpix, nextpix) = infoptr2->firstpix;

    infoptr1->lastpix = infoptr2->lastpix;

    }

  return;

  }

/********************************* sortit ************************************/

/*

build the object structure.

*/

void  sortit(picstruct *field, picstruct *dfield, picstruct *wfield,