/* Last edited on 2006-11-21 03:26:26 by stolfi */

void read_input_file_header(FILE *rd, pnm_image_t **hd_in, pnm_format_t *fmt_in)
  { /* Allocate header: */
    pnm_image_t *hd = (pnm_image_t *)malloc(sizeof(pnm_image_t));
    assert(hd != NULL);
    /* Leave pixel arrays as NULL: */
    hd->pgm_pix = (pixval**)NULL;
    hd->ppm_pix = (pixel**)NULL;
    /* Read header: */
    int fmt;
    pnm_readpnminit(rd, &(hd->cols), &(hd->rows), &(hd->maxval), &fmt);
    pm_message("input format = %i%i maxval = %d cols = %d rows = %d", 
      (fmt >> 8)&255, fmt&255, hd->maxval, hd->rows, hd->cols);
    (*hd_in) = hd;
    (*fmt_in) = fmt;
  }

void make_output_file_header(pnm_image_t *hd_in, pnm_format_t fmt_in, pnm_image_t **hd_ot, pnm_format_t *fmt_ot)
  { /* Allocate header: */
    pnm_image_t *hd = (pnm_image_t *)malloc(sizeof(pnm_image_t));
    assert(hd != NULL);
    /* Copy input size and type: */
    hd->cols = hd_in->cols;
    hd->rows = hd_in->rows;
    hd->maxval = hd_in->maxval;
    hd->pixtype = hd_in->pixtype;
    /* Leave pixel arrays as NULL: */
    hd->pgm_pix = (pixval**)NULL;
    hd->ppm_pix = (pixel**)NULL;
    /* Choose format: */
    pnm_format_t fmt = fmt_in;
    unsigned int imv = hd_in->maxval; /* To supress a bogus compiler warning */
    switch (fmt_in)
      {
        case PPM_FORMAT:
        case RPPM_FORMAT:
          if (imv > PPM_MAXMAXVAL) 
            { pm_error("PPM maxval must be at most %d", PPM_MAXMAXVAL); }
          break;

        case PGM_FORMAT:
        case RPGM_FORMAT:
          if (imv > PGM_OVERALLMAXVAL) 
            { pm_error("PGM maxval must be at most %d", PGM_OVERALLMAXVAL); }
          break;

        case PBM_FORMAT:
        case RPBM_FORMAT:
          if (imv != 1) 
            { pm_error("PBM maxval should be 1"); }
          /* Promote PBM to PGM: */
          hd->maxval = 255;
          fmt = ( fmt_in == PBM_FORMAT ? PGM_FORMAT : RPGM_FORMAT );
          pm_message("promoting input PBM file to PGM (maxval = %d)", hd->maxval);
          break;

        default:
          pm_error("bad input file format");
    }
    
    (*hd_ot) = hd;
    (*fmt_ot) = fmt;
  }

void write_output_file_header(FILE *wr, pnm_image_t *hd_ot, pnm_format_t fmt_ot)
  { pnm_writepnminit(wr, hd_ot->cols, hd_ot->rows, hd_ot->maxval, fmt_ot, FALSE); }