diff --git a/tools/convbdf.c b/tools/convbdf.c
old mode 100644
new mode 100755
index aae5b43..07808df
--- a/tools/convbdf.c
+++ b/tools/convbdf.c
@@ -334,6 +334,10 @@ int bdf_read_header(FILE *fp, struct font* pf)
     char buf[256];
     char facename[256];
     char copyright[256];
+    int bbw;
+    int bbh;
+    int bbx;
+    int bby;
 
     /* set certain values to errors for later error checking*/
     pf->defaultchar = -1;
@@ -418,6 +422,24 @@ int bdf_read_header(FILE *fp, struct font* pf)
             }
             continue;
         }
+
+        /* BBX
+         * pf->ascent, pf->descent are set to the size suitable for the font.
+         */
+        if (isprefix(buf, "BBX ")) {
+            if (sscanf(buf, "BBX %d %d %d %d", &bbw, &bbh, &bbx, &bby) != 4) {
+                fprintf(stderr, "Error: bad 'BBX'\n");
+                return 0;
+            }
+
+            if (bbh + bby > pf->ascent)
+                pf->ascent = bbh + bby;
+            if (-bby > pf->descent)
+                pf->descent = -bby;
+
+            continue;
+        }
+
         if (strequal(buf, "ENDFONT"))
             break;
     }
@@ -427,6 +449,11 @@ int bdf_read_header(FILE *fp, struct font* pf)
         fprintf(stderr, "Error: Invalid BDF file, requires FONT_ASCENT/FONT_DESCENT/ENCODING\n");
         return 0;
     }
+    if (pf->ascent > pf->fbbh + pf->fbby)
+        pf->ascent = pf->fbbh + pf->fbby;
+    if (pf->fbby < 0 && pf->descent > -pf->fbby)
+        pf->descent = -pf->fbby;
+
     pf->height = pf->ascent + pf->descent;
 
     /* calc default char*/
@@ -473,6 +500,7 @@ int bdf_read_bitmaps(FILE *fp, struct font* pf)
     int encodetable = 0;
     int l;
     char buf[256];
+    int r;
 
     /* reset file pointer*/
     fseek(fp, 0L, SEEK_SET);
@@ -561,6 +589,10 @@ int bdf_read_bitmaps(FILE *fp, struct font* pf)
                 if (isprefix(buf, "ENDCHAR"))
                     break;
 
+                r = pf->ascent - bby - bbh + i;
+                if (r < 0 || r >= pf->height)
+                    continue;
+
                 hexnibbles = strlen(buf);
                 for (k=0; k<ch_words; ++k) {
                     int ndx = k * BITMAP_NIBBLES;
@@ -576,12 +608,10 @@ int bdf_read_bitmaps(FILE *fp, struct font* pf)
                                        ndx, ndx+BITMAP_NIBBLES-1-padnibbles);
                     value <<= padnibbles * BITMAP_NIBBLES;
 
-                    BM(pf->height - pf->descent - bby - bbh + i, k) |=
-                        value >> bbx;
+                    BM(r, k) |= value >> bbx;
                     /* handle overflow into next image word*/
                     if (bbx) {
-                        BM(pf->height - pf->descent - bby - bbh + i, k+1) =
-                            value << (BITMAP_BITSPERIMAGE - bbx);
+                        BM(r, k+1) = value << (BITMAP_BITSPERIMAGE - bbx);
                     }
                 }
             }