diff --git a/read_mp.py b/read_mp.py
index fb8f5b3..2d60534 100755
--- a/read_mp.py
+++ b/read_mp.py
@@ -13,11 +13,17 @@
 # - initial version
 
 import argparse
+from PIL import Image
+import os
 
 version = "0.0.1"
 
 
-def read_tiles(fname):
+def dump_offsets(fname):
+    # get file size
+#    fbytes = os.path.getsize(fname)
+#    img = Image.new('1', (1024, fbytes // 1024 + 1024), "white")
+#    pixels = img.load()
     with open(fname, "rb") as f:
         pos = 0
         oldpos = 0
@@ -27,17 +33,41 @@ def read_tiles(fname):
                 b = b + f.read(3)
                 if b == b'\x43\x49\x53\x33': # CIS3
                     #print(b.decode(), f.read(7))
+#                    pixels[pos % 1024, pos // 1024] = 1
                     print(pos, pos - oldpos)
                     oldpos = pos
                 pos += 3
+#        fbase, fext = os.path.splitext(fname)
+#        img.save(fbase + ".png", "PNG")
 
 
+def extract(finname, foutname, offset):
+    with open(finname, "rb") as fin, open(foutname, 'wb') as fout:
+        fin.seek(offset - 1)
+        b = fin.read(4)
+        fout.write(b)
+        while ((b := fin.read(1))):
+            if b == b'\x43':                 # C
+                b = b + fin.read(3)
+                if b == b'\x43\x49\x53\x33': # CIS3
+                    return
+                else:
+                    fout.write(b)
+            else:
+                fout.write(b)
+
 
 if __name__ == '__main__':
     parser = argparse.ArgumentParser(description='read .mp files.', formatter_class=argparse.ArgumentDefaultsHelpFormatter)
     parser.add_argument('input', type=str, help='input file')
+    parser.add_argument('-c', '--command', choices=['offsets', 'extract'], default='offsets')
+    parser.add_argument('--offset', type=int, help='offset to extract')
+    parser.add_argument('-o', '--out', type=str, help='output file')
     parser.add_argument('-v', '--version', action="version", version="%(prog)s " + version)
 
     args = parser.parse_args()
 
-    read_tiles(args.input)
+    if args.command == 'offsets':
+        dump_offsets(args.input)
+    elif args.command == 'extract':
+        extract(args.input, args.out, args.offset)