lsst.pipe.drivers gef6abdcebb+e939f1dbc3
checksum.py
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1import hashlib
2import zlib
3import pickle
4
5import lsst.afw.image as afwImage
6
7__all__ = ["checksum", ]
8
9# Image types to support
10exposureTypes = (afwImage.ExposureF, afwImage.ExposureD,)
11maskedImageTypes = (afwImage.MaskedImageF, afwImage.MaskedImageD,)
12decoratedImageTypes = (afwImage.DecoratedImageF, afwImage.DecoratedImageD,)
13imageTypes = (afwImage.ImageF, afwImage.ImageD, afwImage.ImageI,)
14
15PROTOCOL = 2 # Pickling protocol
16
17# Functions for creating the checksum
18sumFunctions = {
19 "CRC32": lambda obj: zlib.crc32(pickle.dumps(obj, PROTOCOL)),
20 "MD5": lambda obj: hashlib.md5(pickle.dumps(obj, PROTOCOL)).hexdigest(),
21}
22
23
24def checksum(obj, header=None, sumType="MD5"):
25 """!Calculate a checksum of an object
26
27 We have special handling for images (e.g., breaking a MaskedImage into
28 its various components), but the object may be any picklable type.
29
30 @param obj Object for which to calculate the checksum
31 @param header FITS header (PropertyList) to update with checksum values, or None
32 @param sumType Type of checksum to calculate
33 @return dict with header keyword,value pairs
34 """
35 assert sumType in sumFunctions, "Unknown sumType: %s" % (sumType,)
36 func = sumFunctions[sumType]
37
38 results = {}
39
40 if isinstance(obj, exposureTypes):
41 obj = obj.getMaskedImage()
42 if isinstance(obj, decoratedImageTypes):
43 obj = obj.getImage()
44
45 if isinstance(obj, maskedImageTypes):
46 results[sumType + "_IMAGE"] = func(obj.getImage())
47 results[sumType + "_MASK"] = func(obj.getMask())
48 results[sumType + "_VARIANCE"] = func(obj.getVariance())
49 elif isinstance(obj, imageTypes):
50 results[sumType + "_IMAGE"] = func(obj)
51 else:
52 results[sumType] = func(obj)
53
54 if header is not None:
55 for k, v in results.items():
56 header.add(k, v)
57
58 return results
def checksum(obj, header=None, sumType="MD5")
Calculate a checksum of an object.
Definition: checksum.py:24