return MNG_NOERROR;
}

/* ************************************************************************** */
/* B004 */
#endif /* MNG_INCLUDE_WRITE_PROCS */
/* B004 */
/* ************************************************************************** */
/* *                                                                        * */
/* * chunk read functions                                                   * */
/* *                                                                        * */
/* ************************************************************************** */

#ifdef MNG_INCLUDE_READ_PROCS

/* ************************************************************************** */

READ_CHUNK (mng_read_ihdr)
{
#ifdef MNG_SUPPORT_TRACE
  MNG_TRACE (pData, MNG_FN_READ_IHDR, MNG_LC_START)
#endif

  if (iRawlen != 13)                   /* length oke ? */
    MNG_ERROR (pData, MNG_INVALIDLENGTH)
                                       /* only allowed inside PNG or MNG */
  if ((pData->eSigtype != mng_it_png) && (pData->eSigtype != mng_it_mng))
    MNG_ERROR (pData, MNG_CHUNKNOTALLOWED)
                                       /* sequence checks */
  if ((pData->eSigtype == mng_it_png) && (pData->iChunkseq > 1))
    MNG_ERROR (pData, MNG_SEQUENCEERROR)

#ifdef MNG_INCLUDE_JNG
  if ((pData->bHasIHDR) || (pData->bHasBASI) || (pData->bHasIDAT) || (pData->bHasJHDR))
#else
  if ((pData->bHasIHDR) || (pData->bHasBASI) || (pData->bHasIDAT))
#endif
    MNG_ERROR (pData, MNG_SEQUENCEERROR)

  pData->bHasIHDR      = MNG_TRUE;     /* indicate IHDR is present */
                                       /* and store interesting fields */
  if ((!pData->bHasDHDR) || (pData->iDeltatype == MNG_DELTATYPE_NOCHANGE))
  {
    pData->iDatawidth  = mng_get_uint32 (pRawdata);
    pData->iDataheight = mng_get_uint32 (pRawdata+4);
  }
  
  pData->iBitdepth     = *(pRawdata+8);
  pData->iColortype    = *(pRawdata+9);
  pData->iCompression  = *(pRawdata+10);
  pData->iFilter       = *(pRawdata+11);
  pData->iInterlace    = *(pRawdata+12);

#if defined(MNG_NO_16BIT_SUPPORT)
  pData->iPNGmult = 1;
  pData->iPNGdepth = pData->iBitdepth;

  if (pData->iBitdepth > 8)
    {
      pData->iBitdepth = 8;
      pData->iPNGmult = 2;
    }
#endif

  if ((pData->iBitdepth !=  8)      /* parameter validity checks */
      && (pData->iBitdepth !=  1) &&
      (pData->iBitdepth !=  2) &&
      (pData->iBitdepth !=  4)
#ifndef MNG_NO_16BIT_SUPPORT
      && (pData->iBitdepth != 16)   
#endif
      )
    MNG_ERROR (pData, MNG_INVALIDBITDEPTH)

  if ((pData->iColortype != MNG_COLORTYPE_GRAY   ) &&
      (pData->iColortype != MNG_COLORTYPE_RGB    ) &&
      (pData->iColortype != MNG_COLORTYPE_INDEXED) &&
      (pData->iColortype != MNG_COLORTYPE_GRAYA  ) &&
      (pData->iColortype != MNG_COLORTYPE_RGBA   )    )
    MNG_ERROR (pData, MNG_INVALIDCOLORTYPE)

  if ((pData->iColortype == MNG_COLORTYPE_INDEXED) && (pData->iBitdepth > 8))
    MNG_ERROR (pData, MNG_INVALIDBITDEPTH)

  if (((pData->iColortype == MNG_COLORTYPE_RGB    ) ||
       (pData->iColortype == MNG_COLORTYPE_GRAYA  ) ||
       (pData->iColortype == MNG_COLORTYPE_RGBA   )    ) &&
      (pData->iBitdepth < 8                            )    )
    MNG_ERROR (pData, MNG_INVALIDBITDEPTH)

  if (pData->iCompression != MNG_COMPRESSION_DEFLATE)
    MNG_ERROR (pData, MNG_INVALIDCOMPRESS)

#if defined(FILTER192) || defined(FILTER193)
  if ((pData->iFilter != MNG_FILTER_ADAPTIVE ) &&
#if defined(FILTER192) && defined(FILTER193)
      (pData->iFilter != MNG_FILTER_DIFFERING) &&
      (pData->iFilter != MNG_FILTER_NOFILTER )    )
#else
#ifdef FILTER192
      (pData->iFilter != MNG_FILTER_DIFFERING)    )
#else
      (pData->iFilter != MNG_FILTER_NOFILTER )    )
#endif
#endif
    MNG_ERROR (pData, MNG_INVALIDFILTER)
#else
  if (pData->iFilter)
    MNG_ERROR (pData, MNG_INVALIDFILTER)
#endif

  if ((pData->iInterlace != MNG_INTERLACE_NONE ) &&
      (pData->iInterlace != MNG_INTERLACE_ADAM7)    )
    MNG_ERROR (pData, MNG_INVALIDINTERLACE)

#ifdef MNG_SUPPORT_DISPLAY 
#ifndef MNG_NO_DELTA_PNG
  if (pData->bHasDHDR)                 /* check the colortype for delta-images ! */
  {
    mng_imagedatap pBuf = ((mng_imagep)pData->pObjzero)->pImgbuf;

    if (pData->iColortype != pBuf->iColortype)
    {
      if ( ( (pData->iColortype != MNG_COLORTYPE_INDEXED) ||
             (pBuf->iColortype  == MNG_COLORTYPE_GRAY   )    ) &&
           ( (pData->iColortype != MNG_COLORTYPE_GRAY   ) ||
             (pBuf->iColortype  == MNG_COLORTYPE_INDEXED)    )    )
        MNG_ERROR (pData, MNG_INVALIDCOLORTYPE)
    }
  }
#endif
#endif

  if (!pData->bHasheader)              /* first chunk ? */
  {
    pData->bHasheader = MNG_TRUE;      /* we've got a header */
    pData->eImagetype = mng_it_png;    /* then this must be a PNG */
    pData->iWidth     = pData->iDatawidth;
    pData->iHeight    = pData->iDataheight;
                                       /* predict alpha-depth ! */
    if ((pData->iColortype == MNG_COLORTYPE_GRAYA  ) ||
        (pData->iColortype == MNG_COLORTYPE_RGBA   )    )
      pData->iAlphadepth = pData->iBitdepth;
    else
    if (pData->iColortype == MNG_COLORTYPE_INDEXED)
      pData->iAlphadepth = 8;          /* worst case scenario */
    else
      pData->iAlphadepth = 1;  /* Possible tRNS cheap binary transparency */
                                       /* fits on maximum canvas ? */
    if ((pData->iWidth > pData->iMaxwidth) || (pData->iHeight > pData->iMaxheight))
      MNG_WARNING (pData, MNG_IMAGETOOLARGE)

    if (pData->fProcessheader)         /* inform the app ? */
      if (!pData->fProcessheader (((mng_handle)pData), pData->iWidth, pData->iHeight))
        MNG_ERROR (pData, MNG_APPMISCERROR)
  }

  if (!pData->bHasDHDR)
    pData->iImagelevel++;              /* one level deeper */

#ifdef MNG_SUPPORT_DISPLAY
  {
    mng_retcode iRetcode = mng_process_display_ihdr (pData);

    if (iRetcode)                      /* on error bail out */
      return iRetcode;
  }
#endif /* MNG_SUPPORT_DISPLAY */

#ifdef MNG_STORE_CHUNKS
  if (pData->bStorechunks)
  {                                    /* initialize storage */
    mng_retcode iRetcode = ((mng_chunk_headerp)pHeader)->fCreate (pData, pHeader, ppChunk);

    if (iRetcode)                      /* on error bail out */
      return iRetcode;
                                       /* fill the fields */
    ((mng_ihdrp)*ppChunk)->iWidth       = mng_get_uint32 (pRawdata);
    ((mng_ihdrp)*ppChunk)->iHeight      = mng_get_uint32 (pRawdata+4);
    ((mng_ihdrp)*ppChunk)->iBitdepth    = pData->iBitdepth;
    ((mng_ihdrp)*ppChunk)->iColortype   = pData->iColortype;
    ((mng_ihdrp)*ppChunk)->iCompression = pData->iCompression;
    ((mng_ihdrp)*ppChunk)->iFilter      = pData->iFilter;
    ((mng_ihdrp)*ppChunk)->iInterlace   = pData->iInterlace;
  }
#endif /* MNG_STORE_CHUNKS */

#ifdef MNG_SUPPORT_TRACE
  MNG_TRACE (pData, MNG_FN_READ_IHDR, MNG_LC_END)
#endif

  return MNG_NOERROR;                  /* done */
}

/* ************************************************************************** */

READ_CHUNK (mng_read_plte)
{
#if defined(MNG_SUPPORT_DISPLAY) || defined(MNG_STORE_CHUNKS)
  mng_uint32  iX;
  mng_uint8p  pRawdata2;
#endif
#ifdef MNG_SUPPORT_DISPLAY
  mng_uint32  iRawlen2;
#endif

#ifdef MNG_SUPPORT_TRACE
  MNG_TRACE (pData, MNG_FN_READ_PLTE, MNG_LC_START)
#endif
                                       /* sequence checks */
  if ((!pData->bHasMHDR) && (!pData->bHasIHDR) &&
      (!pData->bHasBASI) && (!pData->bHasDHDR)    )
    MNG_ERROR (pData, MNG_SEQUENCEERROR)

#ifdef MNG_INCLUDE_JNG
  if ((pData->bHasIDAT) || (pData->bHasJHDR))
#else
  if (pData->bHasIDAT)
#endif  
    MNG_ERROR (pData, MNG_SEQUENCEERROR)
                                       /* multiple PLTE only inside BASI */
  if ((pData->bHasPLTE) && (!pData->bHasBASI))
    MNG_ERROR (pData, MNG_MULTIPLEERROR)
                                       /* length must be multiple of 3 */
  if (((iRawlen % 3) != 0) || (iRawlen > 768))
    MNG_ERROR (pData, MNG_INVALIDLENGTH)

  if ((pData->bHasIHDR) || (pData->bHasBASI) || (pData->bHasDHDR))
  {                                    /* only allowed for indexed-color or
                                          rgb(a)-color! */
    if ((pData->iColortype != 2) && (pData->iColortype != 3) && (pData->iColortype != 6))
      MNG_ERROR (pData, MNG_CHUNKNOTALLOWED)
                                       /* empty only allowed if global present */
    if ((iRawlen == 0) && (!pData->bHasglobalPLTE))
        MNG_ERROR (pData, MNG_CANNOTBEEMPTY)
  }
  else
  {
    if (iRawlen == 0)                  /* cannot be empty as global! */
      MNG_ERROR (pData, MNG_CANNOTBEEMPTY)
  }

  if ((pData->bHasIHDR) || (pData->bHasBASI) || (pData->bHasDHDR))
    pData->bHasPLTE = MNG_TRUE;        /* got it! */
  else
    pData->bHasglobalPLTE = MNG_TRUE;

  pData->iPLTEcount = iRawlen / 3;  

#ifdef MNG_SUPPORT_DISPLAY
  if ((pData->bHasIHDR) || (pData->bHasBASI) || (pData->bHasDHDR))
  {
    mng_imagep     pImage;
    mng_imagedatap pBuf;

#ifndef MNG_NO_DELTA_PNG
    if (pData->bHasDHDR)               /* processing delta-image ? */
    {                                  /* store in object 0 !!! */
      pImage           = (mng_imagep)pData->pObjzero;
      pBuf             = pImage->pImgbuf;
      pBuf->bHasPLTE   = MNG_TRUE;     /* it's definitely got a PLTE now */
      pBuf->iPLTEcount = iRawlen / 3;  /* this is the exact length */
      pRawdata2        = pRawdata;     /* copy the entries */

      for (iX = 0; iX < iRawlen / 3; iX++)
      {
        pBuf->aPLTEentries[iX].iRed   = *pRawdata2;
        pBuf->aPLTEentries[iX].iGreen = *(pRawdata2+1);
        pBuf->aPLTEentries[iX].iBlue  = *(pRawdata2+2);

        pRawdata2 += 3;
      }
    }
    else
#endif
    {                                  /* get the current object */
      pImage = (mng_imagep)pData->pCurrentobj;

      if (!pImage)                     /* no object then dump it in obj 0 */
        pImage = (mng_imagep)pData->pObjzero;

      pBuf = pImage->pImgbuf;          /* address the object buffer */
      pBuf->bHasPLTE = MNG_TRUE;       /* and tell it it's got a PLTE now */

      if (!iRawlen)                    /* if empty, inherit from global */
      {
        pBuf->iPLTEcount = pData->iGlobalPLTEcount;
        MNG_COPY (pBuf->aPLTEentries, pData->aGlobalPLTEentries,
                  sizeof (pBuf->aPLTEentries))

        if (pData->bHasglobalTRNS)     /* also copy global tRNS ? */
        {                              /* indicate tRNS available */
          pBuf->bHasTRNS = MNG_TRUE;

          iRawlen2  = pData->iGlobalTRNSrawlen;
          pRawdata2 = (mng_uint8p)(pData->aGlobalTRNSrawdata);
                                       /* global length oke ? */
          if ((iRawlen2 == 0) || (iRawlen2 > pBuf->iPLTEcount))
            MNG_ERROR (pData, MNG_GLOBALLENGTHERR)
                                       /* copy it */
          pBuf->iTRNScount = iRawlen2;
          MNG_COPY (pBuf->aTRNSentries, pRawdata2, iRawlen2)
        }
      }
      else
      {                                /* store fields for future reference */
        pBuf->iPLTEcount = iRawlen / 3;
        pRawdata2        = pRawdata;

        for (iX = 0; iX < pBuf->iPLTEcount; iX++)