diff --git a/makedef.py b/makedef.py
new file mode 100644
index 0000000..4a2ec16
--- /dev/null
+++ b/makedef.py
@@ -0,0 +1,95 @@
+#!/usr/bin/env python
+
+import os
+import re
+import struct
+from collections import defaultdict
+from PIL import Image
+
+def makedef(indir, outdir):
+    infiles = defaultdict(list)
+    sig = None
+    fnames = set()
+    # sanity checks and fill infiles dict
+    for f in os.listdir(indir):
+        m = re.match('(\d+)_([A-Za-z0-9_]+)_(\d\d)_(\d\d)_([A-Za-z0-9_]+)_(\d+)x(\d+)_(\d+)x(\d+).png', f)
+        if not m:
+            continue
+        t,p,bid,j,fn,fw,fh,lm,tm = m.groups()
+        t,bid,j,fw,fh,lm,tm = int(t),int(bid),int(j),int(fw),int(fh),int(lm),int(tm)
+        im = Image.open(os.sep.join([indir,f]))
+        w,h = im.size
+        if im.mode != 'P':
+            print "input images must have a palette"
+            return False
+        cursig =(t,p,fw,fh,im.getpalette())
+        if not sig:
+            sig = cursig
+        else:
+            if sig != cursig:
+                print "sigs must match - got:"
+                print sig
+                print cursig
+                return False
+        if fn in fnames:
+            print "duplicate filename: %s"%fn
+            return False
+        if w%16 != 0:
+            print "width must be divisible by 16"
+            return False
+        if len(fn) > 9:
+            print "filename can't be longer than 9 bytes"
+            return False
+        fnames.add(fn)
+        infiles[bid].append((im,t,p,j,fn,fw,fh,lm,tm))
+
+    # check if j values for all bids are correct and sort them in j order in the process
+    for bid in infiles:
+        infiles[bid].sort(key=lambda t: t[3])
+        for k,(_,_,bid,j,_,_,_,_,_) in enumerate(infiles[bid]):
+            if k != j:
+                print "incorrect j value %d for bid %d should be %d"%(j,bid,k)
+
+    t,p,fw,fh,pal = cursig
+    outf = open(outdir+"/"+p+".def", "w+")
+
+    # write the header
+    outf.write(struct.pack("<IIII", t,fw,fh,len(infiles)))
+    # write the palette
+    outf.write(struct.pack("768B", *pal))
+
+    # the bid table requires 16 bytes for each bid and 13+4 bytes for each entry
+    bidtablesize = 16*len(infiles)+sum(len(l)*(13+4) for l in infiles.values())
+    # the position after the bid table is the header plus palette plus bid table size 
+    curoffset = 16+768+bidtablesize
+
+    for bid,l in infiles.items():
+        # write bid and number of frames
+        outf.write(struct.pack("<IIII",bid,len(l),0,0))
+        # write filenames
+        for _,_,_,_,fn,_,_,_,_ in l:
+            outf.write(struct.pack("13s", fn+".pcx"))
+        # write data offsets
+        for im,_,_,_,_,_,_,_,_ in l:
+            outf.write(struct.pack("<I",curoffset))
+            w,h = im.size
+            print curoffset
+            # every image occupies one byte per pixel plus 32 byte header
+            curoffset += w*h+32
+
+    for bid,l in infiles.items():
+        for im,_,_,_,_,fw,fh,lm,tm in l:
+            w,h = im.size
+            outf.write(struct.pack("<IIIIIIii",w*h,0,fw,fh,w,h,lm,tm))
+            buf = ''.join([chr(i) for i in list(im.getdata())])
+            outf.write(buf)
+            print outf.tell()
+    return True
+
+if __name__ == '__main__':
+    import sys
+    if len(sys.argv) != 3:
+        print "usage: %s indir outdir"%sys.argv[0]
+        exit(1)
+    ret = makedef(sys.argv[1], sys.argv[2])
+    exit(0 if ret else 1)