--- a/imagetool-uncompressed.py
+++ b/imagetool-uncompressed.py
@@ -3,15 +3,23 @@
 import os
 import re
 import sys
+import argparse
 
-try:
-   kernel_image = sys.argv[1]
-except:
-   kernel_image = ""
-
-if kernel_image == "":
-  print("usage : imagetool-uncompressed.py <kernel image>");
-  sys.exit(0)
+parser = argparse.ArgumentParser(description='Prepare kernel files for Raspberry Pi bootloader')
+parser.add_argument('--force', '-f', action='store_true', default=False,
+  help='overwrite target file')
+parser.add_argument('kernel',
+  help='kernel file from /usr/src/linux*/arch/arm/boot/Image')
+parser.add_argument('bootimage',
+  help='file to be placed in /boot/kernel.img')
+args = parser.parse_args()
+if os.path.exists(args.bootimage) and not args.force:
+  print('Target file exists, use --force to override')
+  sys.exit(1)
+
+f = open(args.kernel, 'rb')
+kernel_image = f.read()
+f.close()
    
 re_line = re.compile(r"0x(?P<value>[0-9a-f]{8})")
 
@@ -35,11 +43,10 @@
 load_to_mem("boot-uncompressed.txt", 0x00000000)
 load_to_mem("args-uncompressed.txt", 0x00000100)
 
-f = open("first32k.bin", "wb")
+f = open(args.bootimage, "wb")
 
 for m in mem:
    f.write(chr(m))
 
+f.write(kernel_image)
 f.close()
-
-os.system("cat first32k.bin " + kernel_image + " > kernel.img")