1 files changed, 55 insertions, 0 deletions
diff --git a/astro/fits/fitsimgsub.py b/astro/fits/fitsimgsub.py
new file mode 100755
index 0000000..cae0190
--- /dev/null
+++ b/astro/fits/fitsimgsub.py
@@ -0,0 +1,55 @@
+#!/usr/bin/env python3
+#
+# Copyright (c) Weitian LI <weitian@aaronly.me>
+# MIT license
+#
+
+"""
+Subtract a FITS image by one or more FITS images of same shape.
+"""
+
+import os
+import sys
+import argparse
+
+from astropy.io import fits
+
+
+def main():
+    parser = argparse.ArgumentParser(
+        description="Subtract a FITS image by >=1 images of same shape")
+    parser.add_argument("-C", "--clobber", action="store_true",
+                        help="overwrite existing files")
+    parser.add_argument("-1", "--infile1", required=True,
+                        help="the FITS image from which to be subtracted")
+    parser.add_argument("-2", "--infile2", nargs="+",
+                        help="one or more FITS images to be subtracted by")
+    parser.add_argument("-o", "--outfile", required=True,
+                        help="filename of subtracted FITS image")
+    args = parser.parse_args()
+
+    if os.path.exists(args.outfile):
+        if args.clobber:
+            os.remove(args.outfile)
+            print("WARNING: removed existing output file: %s" % args.outfile)
+        else:
+            raise OSError("output file already exists: %s" % args.outfile)
+
+    with fits.open(args.infile1) as f:
+        image = f[0].data
+        header = f[0].header
+        print("Opened FITS image: %s" % args.infile1)
+        print("Image shape: %s" % str(list(reversed(image.shape))))
+
+    for fn in args.infile2:
+        print("Subtracting FITS image: %s ..." % fn)
+        image -= fits.open(fn)[0].data
+
+    header.add_history(" ".join(sys.argv))
+    hdu = fits.PrimaryHDU(data=image, header=header)
+    hdu.writeto(args.outfile)
+    print("Wrote subtracted FITS image to: %s" % args.outfile)
+
+
+if __name__ == "__main__":
+    main()