STY: Move functions within _xobj_to_image to a private module

[MartinThoma]

This PR only moves code. It does not change any logic.

[codecov]

Codecov Report

Patch coverage: 93.38% and no project coverage change.

Comparison is base (5bfbae7) 94.25% compared to head (9309c35) 94.26%.
Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2182   +/-   ##
=======================================
  Coverage   94.25%   94.26%           
=======================================
  Files          42       43    +1     
  Lines        7559     7566    +7     
  Branches     1488     1488           
=======================================
+ Hits         7125     7132    +7     
  Misses        266      266           
  Partials      168      168           

Files Changed	Coverage Δ
pypdf/_xobj_image_helpers.py	93.33% <93.33%> (ø)
pypdf/filters.py	95.04% <100.00%> (+0.50%)	⬆️

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[pubpub-zz]

Are you sure this will "reduce" the complexity ?
Also In order to ease reading, wouldn't it be better to have also _xobj_to_image in the new file ?

[MartinThoma]

I think nested functions are typically more complex then non-nested ones. And passing parameters explicitly is less complex than using global variables.

In order to ease reading, wouldn't it be better to have also _xobj_to_image in the new file ?

I agree 👍

[MartinThoma]

Ah, damn, if I do that, then it becomes more complicated with PIL (which might not be installed) -.-

[MartinThoma]

@pubpub-zz I'm not super happy with this PR as I agree that _xobj_to_image should also be in the new module.

However, I think this slightly improves the situation. It does reduce the file size quite a bit and hopefully in a meaningful way: If PRs in future touch often just filters.py or _xobj_image_helpers.py (one, not both at the same time) it was a good PR. Then it made merge conflicts less likely.

If that is not the case or if you're telling me that this made the situation worse for you, I'll undo it.