[antond-weta]

Add double-application guards to colour transform functions so they cannot be executed twice on the same image. Each function marks its output image buffer with an rta:* attribute on success, and returns false with an error message if the attribute is already present on the source:

• apply_matrix -> rta:AppliedColourTransformMatrix
• apply_scale -> rta:AppliedScale
• apply_crop -> rta:AppliedCrop
• apply_vignette_map -> rta:AppliedLensVignetteCorrection
• apply_distortion_map -> rta:AppliedLensDistortionCorrection
• apply_aberration_map -> rta:AppliedLensChromaticAberrationCorrection

Expand remove_diagnostic_attributes to remove all six attributes declared in attributes.h, and add a --keep-diagnostic-attributes CLI flag (linked to ImageConverter::Settings::keep_diagnostic_attributes) that controls whether these attributes are stripped from the output EXR in save_image().

Add Python binding for keep_diagnostic_attributes and regenerate the Python API docs.

Add unit tests verifying each guard fails on the second application: test_apply_matrix_twice, test_apply_crop_twice, test_apply_scale_twice, test_remove_diagnostic_attributes, test_apply_vignette_map_twice, test_apply_distortion_map_twice, test_apply_aberration_map_twice.

Also fix a pre-existing signature mismatch in prepare_transform_spectral (declaration had 5 params, definition had 6 with out_found_illuminant) and update all test call sites.

Assisted-by: nemotron-3.5-super-vl-free

Description

Tests

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  line in the pull request description above.
• I have updated the documentation, if applicable. (Check if there is no
  need to update the documentation, for example if this is a bug fix that
  doesn't change the API.)
• I have ensured that the change is tested somewhere in the testsuite
  (adding new test cases if necessary).
• My code follows the prevailing code style of this project. If I haven't
  already run clang-format before submitting, I definitely will look at the CI
  test that runs clang-format and fix anything that it highlights as being
  nonconforming.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 96.22642% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 92.04%. Comparing base (5d07dda) to head (4334804).

Files with missing lines	Patch %	Lines
src/cpp/rawtoaces_util/image_converter.cpp	95.50%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #365      +/-   ##
==========================================
+ Coverage   91.79%   92.04%   +0.24%     
==========================================
  Files          17       17              
  Lines        3876     3959      +83     
  Branches      582      591       +9     
==========================================
+ Hits         3558     3644      +86     
+ Misses        318      315       -3     

Files with missing lines	Coverage Δ
src/cpp/include/rawtoaces/image_converter.h	100.00% <100.00%> (ø)
src/cpp/rawtoaces_util/lens_correction.cpp	99.35% <100.00%> (+0.03%)	⬆️
src/cpp/rawtoaces_util/image_converter.cpp	81.01% <95.50%> (+1.02%)	⬆️

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[soswow]

minor things left:

Stale parameter comment	prepare_transform_spectral still does not document out_found_illuminant.
Lens merge untested	The lens tests call the map functions directly, so they never execute the extra_attribs merge.
No-op steps	Default soft crop, an identity matrix, and a scale of 1 still write no attribute. That matches the existing skip in process_buffer.

up to you. LGTM