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diff --git a/bin/correct_exposure.py b/bin/correct_exposure.py
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+++ b/bin/correct_exposure.py
@@ -0,0 +1,127 @@
+#!/usr/bin/env python3
+#
+# Copyright (c) 2017 Weitian LI <liweitianux@live.com>
+# MIT license
+
+"""
+Correct (counts) image for exposure by dividing the exposure map.
+
+References
+----------
+* Chandra Memo: An Introduction to Exposure Map
+  http://cxc.harvard.edu/ciao/download/doc/expmap_intro.ps
+* CIAO: Single Chip ACIS Exposure Map and Exposure-corrected Image
+  http://cxc.harvard.edu/ciao/threads/expmap_acis_single/
+* CIAO: Multiple Chip ACIS Exposure Map and Exposure-corrected Image
+  http://cxc.harvard.edu/ciao/threads/expmap_acis_multi/
+"""
+
+import os
+import argparse
+import subprocess
+import logging
+
+from _context import acispy
+from acispy.manifest import get_manifest
+from acispy.pfiles import setup_pfiles
+from acispy.image import get_xygrid
+
+
+logging.basicConfig(level=logging.INFO)
+logger = logging.getLogger(__name__)
+
+
+def threshold_image(infile, outfile, expmap, cut="1.5%", clobber=False):
+    """
+    The strongly variable exposure near the edge of a dithered field
+    may produce "hot" pixels when divided into an image.  Therefore,
+    apply a threshold to the image pixels that cuts the pixels with
+    value of exposure less than the threshold.
+    """
+    logger.info("Threshold cut the image: cut=%s" % cut)
+    clobber = "yes" if clobber else "no"
+    subprocess.check_call(["punlearn", "dmimgthresh"])
+    subprocess.check_call([
+        "dmimgthresh", "infile=%s" % infile,
+        "outfile=%s" % outfile, "expfile=%s" % expmap,
+        "cut=%s" % cut,
+        "clobber=%s" % clobber
+    ])
+
+
+def correct_exposure(infile, outfile, expmap, clobber=False):
+    """
+    The strongly variable exposure near the edge of a dithered field
+    may produce "hot" pixels when divided into an image.  Therefore,
+    apply a threshold to the image pixels that cuts the pixels with
+    value of exposure less than the threshold.
+    """
+    logger.info("Correct the image for exposure ...")
+    clobber = "yes" if clobber else "no"
+    subprocess.check_call(["punlearn", "dmimgcalc"])
+    subprocess.check_call([
+        "dmimgcalc", "infile=%s" % infile, "infile2=%s" % expmap,
+        "outfile=%s[PFLUX_IMAGE]" % outfile,
+        "operation=div",
+        "clobber=%s" % clobber
+    ])
+
+
+def main():
+    parser = argparse.ArgumentParser(
+        description="Make spectral-weighted exposure map")
+    parser.add_argument("-C", "--clobber", dest="clobber", action="store_true",
+                        help="overwrite existing file")
+    parser.add_argument("-M", "--update-manifest", dest="update_manifest",
+                        action="store_true",
+                        help="update manifest with newly created images")
+    parser.add_argument("-i", "--infile", dest="infile", required=True,
+                        help="input image file to apply exposure correction")
+    parser.add_argument("-e", "--expmap", dest="expmap",
+                        help="exposure map (default: 'expmap' from manifest)")
+    parser.add_argument("-o", "--outfile", dest="outfile",
+                        help="filename of output exposure-corrected image " +
+                        "(default: append '_expcorr' to the base filename)")
+    args = parser.parse_args()
+
+    setup_pfiles(["dmimgcalc", "dmimgthresh"])
+
+    manifest = get_manifest()
+    if args.expmap:
+        expmap = args.expmap
+    else:
+        expmap = manifest.getpath("expmap", relative=True)
+    if args.outfile:
+        img_expcorr = args.outfile
+    else:
+        img_expcorr = os.path.splitext(args.infile)[0] + "_expcorr.fits"
+    img_thresh = os.path.splitext(args.infile)[0] + "_thresh.fits"
+    logger.info("infile: %s" % args.infile)
+    logger.info("expmap: %s" % expmap)
+    logger.info("output exposure-corrected image: %s" % img_expcorr)
+    logger.info("output threshold-cut counts image: %s" % img_thresh)
+
+    xygrid_infile = get_xygrid(args.infile)
+    xygrid_expmap = get_xygrid(expmap)
+    logger.info("%s:xygrid: %s" % (args.infile, xygrid_infile))
+    logger.info("%s:xygrid: %s" % (expmap, xygrid_expmap))
+    if xygrid_infile != xygrid_expmap:
+        raise ValueError("xygrid: input image and exposure map do not match")
+
+    threshold_image(infile=args.infile, outfile=img_thresh, expmap=expmap,
+                    clobber=args.clobber)
+    correct_exposure(infile=img_thresh, outfile=img_expcorr,
+                     expmap=expmap, clobber=args.clobber)
+
+    if args.update_manifest:
+        logger.info("Add newly created images to manifest ...")
+        key = "img_expcorr"
+        manifest.setpath(key, img_expcorr)
+        logger.info("Added '%s' to manifest: %s" % (key, manifest.get(key)))
+        key = "img_thresh"
+        manifest.setpath(key, img_thresh)
+        logger.info("Added '%s' to manifest: %s" % (key, manifest.get(key)))
+
+
+if __name__ == "__main__":
+    main()