Summary

This PR adds a small Python wrapper to match SIFT descriptors directly (without a database).

Related to #3667.

What’s included

• New pycolmap.SiftMatcher wrapper around COLMAP FeatureMatcher
• GPU matching and CPU brute-force matching supported
• Added docstring explained how to cache descriptors on GPU with image_id and warning that reusing an image_id for different descriptors can produce incorrect results.

Limitation

• CPU FAISS matching (cpu_brute_force_matcher=False) is not supported. See follow-up question.

Example

sift = pycolmap.Sift()
k1, d1 = sift.extract(img1)
k2, d2 = sift.extract(img2)

matcher = pycolmap.SiftMatcher(device=pycolmap.Device.cuda)  # or Device.cpu
matches = matcher.match(d1, d2, image_id1=1, image_id2=2)

Follow-ups

• If this looks good, I can go ahead and implement the MatchGuided function as part of this class.
• For CPU FAISS, do you have any ideas or comments about integrating index caching?