Brightness normalisation

[IgorTatarnikov]

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Description

What is this PR

• Bug fix
• Addition of a new feature
• Other

Why is this PR needed?
There can be large intensity differences between each tile. This PR introduces a method to normalise the intensities between each tile.

What does this PR do?

This is done by assuming that the overlapping area should have equal intensity between each tile. This is used to calculate a scaling factor between two tiles. This scaling factor is applied and the comparison is done for the subsequent tiles. For example say an image contains 4 tiles and each tile overlaps with all other tiles:

The first round of comparisons will calculate scaling factors for tile 1 + 2, 1 + 3, 1 + 4. The scaling factors will be applied lazily to the tiles. The second round of comparisons will calculate scaling factors based on tile 2 + 3, 2 + 4.

The final result will be a num_tiles by num_tiles matrix that contains a scaling factor for each tile comparison.

	tile_1	tile_2	tile_3	tile_4	final_factor
tile_1	1	1	1	1	1
tile_2	0.8	1	1	1	0.8
tile_3	0.9	0.95	1	1	0.855
tile_4	0.6	0.98	0.96	1	0.565

The final factor is calculated as the product of all scaling factors calculated for that tile. This final scaling factor is then applied to the full resolution image prior to fusing/saving to disk.

How has this PR been tested?

Tests added for new functionality.

Is this a breaking change?

No

Checklist:

• The code has been tested locally
• Tests have been added to cover all new functionality (unit & integration)
• The code has been formatted with pre-commit

[codecov]

Codecov Report

Attention: Patch coverage is 98.92473% with 1 line in your changes missing coverage. Please review.

Project coverage is 96.95%. Comparing base (7e5f173) to head (87b9b12).

Files with missing lines	Patch %	Lines
brainglobe_stitch/stitching_widget.py	98.14%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #25      +/-   ##
==========================================
+ Coverage   95.54%   96.95%   +1.41%     
==========================================
  Files           6        6              
  Lines         673      756      +83     
==========================================
+ Hits          643      733      +90     
+ Misses         30       23       -7     

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