mm->vox integers per AFNI 3dmaskdump OUTPUT

gistfile1.txt

AFNI 3dmaskdump OUTPUT:
------------------------------------------------
Appears to use implicit casting and a custom log-based algorithm to convert
coordinate floats to integers:

If user requests integer voxel coordinates (not mm), 3dmaskdump creates them
from internal float voxel coordinates (not mm) using functions in multivector.c:
MV_format_fval(), which calls MV_fval_to_char()

e.g., here 3dmaskdump calls for outputting integer voxel coordinate ijk: 
	666         i = DSET_index_to_ix( input_dset[0] , ii ) ;  /* voxel indexes */
	667         j = DSET_index_to_jy( input_dset[0] , ii ) ;
	668         k = DSET_index_to_kz( input_dset[0] , ii ) ;
	669 
	670         otemp = MV_format_fval((float)i); strcat(obuf,otemp); strcat(obuf," ");
	671         otemp = MV_format_fval((float)j); strcat(obuf,otemp); strcat(obuf," ");
	672         otemp = MV_format_fval((float)k); strcat(obuf,otemp); strcat(obuf," ");

...which invokes the algorithm in lines 395-457 of multivector.c:
	395 void MV_fval_to_char( float qval , char *buf )
	396 {
	397    float aval = fabs(qval) ;
	398    int lv ;
	399    char lbuf[32] ;
	400    int il ;
	401 
	402    /* special case if the value is an integer */
	403 
	404    if( qval == 0.0 ){ strcpy(buf,"0"); return; }
	405 
	406    lv = (fabs(qval) < 99999999.0) ? (int)qval : 100000001 ;
	407 
	408    if( qval == lv && abs(lv) < 100000000 ){
	409       sprintf( buf, "%d" , lv ) ; return ;
	410    }
	411 
	412 /* macro to strip trailing zeros from output */
	413 
	414 #undef  BSTRIP
	415 #define BSTRIP for( il=strlen(lbuf)-1 ;                        \
	416                     il>1 && (lbuf[il]=='0' || lbuf[il]==' ') ; \
	417                     il-- ) lbuf[il] = '\0'
	418 
	419    /* noninteger: choose floating format based on magnitude */
	420 
	421    lv = (int) (10.0001 + log10(aval)) ;
	422 
	423    switch( lv ){
	424 
	425       default:
	426          if( qval > 0.0 ) sprintf( lbuf , "%-12.6e" , qval ) ;
	427          else             sprintf( lbuf , "%-12.5e" , qval ) ;
	428       break ;
	429 
	430       case  6:  /* 0.0001-0.001 */
	431       case  7:  /* 0.001 -0.01  */
	432       case  8:  /* 0.01  -0.1   */
	433       case  9:  /* 0.1   -1     */
	434       case 10:  /* 1     -9.99  */
	435          sprintf( lbuf , "%-9.6f" , qval ) ; BSTRIP ; break ;
	436 
	437       case 11:  /* 10-99.9 */
	438          sprintf( lbuf , "%-9.5f" , qval ) ; BSTRIP ; break ;
	439 
	440       case 12:  /* 100-999.9 */
	441          sprintf( lbuf , "%-9.4f" , qval ) ; BSTRIP ; break ;
	442 
	443       case 13:  /* 1000-9999.9 */
	444          sprintf( lbuf , "%-9.3f" , qval ) ; BSTRIP ; break ;
	445 
	446       case 14:  /* 10000-99999.9 */
	447          sprintf( lbuf , "%-9.2f" , qval ) ; BSTRIP ; break ;
	448 
	449       case 15:  /* 100000-999999.9 */
	450          sprintf( lbuf , "%-9.1f" , qval ) ; BSTRIP ; break ;
	451 
	452       case 16:  /* 1000000-9999999.9 */
	453          sprintf( lbuf , "%-9.0f" , qval ) ; break ;
	454    }
	455 
	456    strcpy(buf,lbuf) ; return ;
	457 }