Handle malformed XMP

[pierotofy]

Hello :hand:

This PR proposes the addition of a second attempt in order to fix faulty XML in XMP tags from cameras that have malformed/invalid XML. It doesn't change the original behavior of the function. It loads BeautifulSoup lazily since I don't think too many cameras have this problem. The lxml library is a requirement for beautifulsoup.

I hope this can be useful to make OpenSfM more stable. 🙏 Let me know if changes are needed?

[YanNoun]

I'm fine with the changes, but I have a few requests :

• Let's imports BeautifulSoup at the top of the file since it is a requirement anyway. Makes the code less obfuscated.
• I had trouble reading and understanding the combination of range loop + try/except. Could we remove the loop and make each step explicit, even if longuer and has nested try/except ? It would be more readable and indicates this is a tricky step part per-se.

[YanNoun]

@pierotofy another thing would be to have at the image that caused the need for this fix and/or the corresponding malformed string so we have proper unit testing for that one, as it gets tricky.

[pierotofy]

Thanks for the recommendations @YanNoun I'll work on the changes and also to provide you with a test case.

[pierotofy]

Suggestions implemented. :+1:

Test case:

from opensfm.exif import EXIF

e = EXIF(open("./DJI_0018.JPG"))
print(e.xmp)

Input image (with corrupted XMP): https://uav4geo.com/static/downloads/DJI_0018.JPG

Before the fix the print statement should fail. After the fix it should work.

The XMP string from the image is:

<?xpacket begin="" id="W5M0MpCehiHzreSzNTczkc9d"?> <x:xmpmeta xmlns:x="adobe:ns:meta/" x:xmptk="XMP Core 4.4.0-Exiv2"> <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"> <rdf:Description rdf:about=""xmlns:xmp="http://ns.adobe.com/xap/1.0/" xmlns:tiff="http://ns.adobe.com/tiff/1.0/" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:drone-dji="http://www.dji.com/drone-dji/1.0/" xmlns:crs="http://ns.adobe.com/camera-raw-settings/1.0/" xmp:ModifyDate="2016-06-23" xmp:CreateDate="2016-06-23" tiff:Make="DJI" tiff:Model="FC300S" dc:format="image/jpeg" drone-dji:AbsoluteAltitude="+198.31" drone-dji:RelativeAltitude="+39.80" drone-dji:GimbalRollDegree="+0.00" drone-dji:GimbalYawDegree="+45.00" drone-dji:GimbalPitchDegree="-89.90" drone-dji:FlightRollDegree="+3.00" drone-dji:FlightYawDegree="+46.00" drone-dji:FlightPitchDegree="+1.80" crs:Version="7.0" crs:HasSettings="False" crs:HasCrop="False" crs:AlreadyApplied="False"/> </rdf:RDF>  </x:xmpmeta>

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[pierotofy]

Mm, is a CLA required now?

Not opposed to signing one, just not sure if I want to sign it via Facebook. :)

[pierotofy]

Signed the CLA through Facebook, but this still fails. :confused:

Edit: ah, just a bit of delay. Check passed. :heavy_check_mark:

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[pierotofy]

CLA signed, rebased the branch, fixed travis CI.

Let me know if further changes are needed :pray:

[pierotofy]

Not sure if there's still interest in merging this one, I can close it if not. :pray: