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utils.py — image enhancement algorithms (mode 9)
- Added classic_he_gray, tidhe_gray, rdfhe_gray, nfldice_gray, betce_gray, sfcef_gray; all support legacy_mode=True.
- Documented intentional deviations from SHINE/MATLAB in-source:
· exact_histogram 'noise' tie-strategy uses centered noise [-level, +level] instead of SHINE match.m's
one-sided rand()*0.1, avoiding systematic upward bias.
· sf_match/spec_match use soft_clip instead of MATLAB's silent uint8 hard-clip, even in legacy_mode
(hard-clip distorts the matched spectrum).
utils.py — validation
- Added sf_match_validation and spec_match_validation (adapted for fft_padding_mode).
- Added corr_rmse_per_item and mean_spectrum (de-duplicate repeated code).
utils.py — metrics
- Added ImageStats and imstats (replicate MATLAB imstats.m).
- Added compute_ambe, compute_mssim, compute_psnr, compute_bp2bpsim, compute_contrast_improvement,
compute_image_entropy.
- Added tidhe_hist_plot.
Options.py
- Added mode=9 standalone_op parameter ('dithering', 'ie_methods'). Mode 9 is no longer dithering-only:
it now groups the non-matching processing options and catalogues the image enhancement methods.
SHINIER.py
- Mode 9 CLI prompts for standalone_op selection.
Bug fixes
ImageProcessor.py — background pixel overflow in modes 7 and 8
- Frequency operations (sf_match, spec_match) produce out-of-range IFFT values for background pixels
(outside the mask, not processed by the following hist_match); with _is_moving_target=True these
accumulate across iterations. Fixed by applying soft_clip when _iter_num == iterations-1 (last outer
iteration) instead of only at _is_last_operation. soft_clip is monotonic, so it preserves the rank
ordering seen by the following hist_match on foreground pixels.
utils.py — rescale_images255 option 3
- Dataset-average min/max normalization could map outlier images outside [0, 255]; added
np.clip(..., 0, 255) after the linear rescaling.
Converter.py — legacy_mode improvements
- forward_color_treatment/backward_color_treatment with legacy_mode=True now explicitly call
rgb2gray(weighting_standard="rec601", matlab_601=True) — equivalent to rgb2ntsc_intensity — matching
the Y channel of MATLAB rgb2ntsc / NTSC-YIQ, and output the Y component.
- Renamed parameter conversion_type -> color_conversion in both methods.
- Added MATLAB_RGB2GRAY_WEIGHTS constant with the exact MATLAB Rec.601 weights.
- Improved legacy_mode docstring: clarifies when the NTSC-YIQ path is taken and its relationship to
Options(legacy_mode=True).
quantify_chroma_loss.py
- Shortened the file name and several function names.
Tests
tests/tools/utils.py
- is_already_done skips only terminal-success statuses; failed/error combos are retried, not cached green.
- prepare_images treats only the first image per buffer cell and drops the unused buffers_other (~12 -> 2 MB).
tests/validation_tests/ImageProcessor_validation_test.py
- Seed authoritative per combo (from_unit_test + proc.seed, then process()); no wall-clock reseed, so
failures reproduce. seed_iter strips volatile paths; combo_hash namespaced by option-space fingerprint.
- Unexpected Options() errors hard-fail (not "invalid"); real coverage accounting replaces the vacuous
cnt>=0 assert.
- 'final' SSIM check hard only for mode 2; composite modes 5-8 gate on final-output SSIM (hard collapse
floor + soft degraded warning). RMSE baseline now uses proc._initial_buffer.
New test files
- tests/unit_tests/Utils_test.py.
- tests/unit_tests/PrunedCoverage_test.py.
- tests/validation_tests/ImageEnhancement_validation_test.py (pixel-exact MATLAB SHA-256 hashes for
TIDHE/RDFHE/NFLDICE/BETCE; pixel-difference bound <= 1 gray level for SFCEF due to FMA rounding).
- tests/assets/image_enhancement_matlab_sha256.json.
- tests/assets/sfcef_matlab_reference/.
Documentation
documentation.md
- Expanded the RGB-to-grayscale section.
- Added "Convolution — FMA and Unit in the Last Place (ULP)".
- Updated mode 9 to document standalone_op and ie_methods.
- Added "Histogram Equalization: Exact Specification and Histogram-Derived Remapping".
- Added algorithm descriptions (sections 5-10): Classic HE, TIDHE, RDFHE, NFLDICE, BETCE, SFCEF.
- Updated the testing section: Utils_test, PrunedCoverage_test, ImageEnhancement_validation_test.
demos.md
- Updated the mode 9 example; split into 9a (standalone_op="ie_methods", with ie_methods selection)
and 9b (standalone_op="dithering").
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Image enhancement
utils.pyAdded six grayscale enhancement methods:
classic_he_graytidhe_grayrdfhe_graynfldice_graybetce_graysfcef_grayAll methods support
legacy_mode=True.Documented two intentional differences from
SHINE/MATLAB:
noisetie strategy inexact_histogramuses centered noise instead of SHINE’s one-sided noise,avoiding upward bias.
sf_matchandspec_matchusesoft_cliprather than MATLAB-style hard clipping, because hard clipping distorts the
matched spectrum.
Mode 9
Mode 9 now supports two standalone operation
groups through
standalone_op:"ie_methods"for imageenhancement
"dithering"for ditheringThe CLI now prompts users to select the
standalone operation.
Validation and metrics
Added:
sf_match_validationspec_match_validationcorr_rmse_per_itemmean_spectrumImageStatsimstatscontrast-improvement, and entropy metrics
tidhe_hist_plotThe spectrum validation functions support
fft_padding_mode.Bug fixes
ImageProcessor.pyFixed background-pixel overflow in modes 7
and 8 by applying
soft_clipduring the final outer iteration. This preventsout-of-range IFFT values from accumulating while preserving foreground rank
ordering before histogram matching.
utils.pyAdded clipping after dataset-level min/max
normalization in
rescale_images255option 3, preventing outlier images fromexceeding
[0, 255].Converter.pyImproved
legacy_modecompatibility:MATLAB-compatible Rec. 601 weights.
MATLAB
rgb2ntsc.MATLAB_RGB2GRAY_WEIGHTS.conversion_typetocolor_conversion.docstrings.
Chroma-loss utilities
Shortened
quantify_chroma_loss.pyandseveral function names.
Tests
Improved test infrastructure:
instead of being treated as cached successes.
first image in each buffer cell and removes unused buffers.
reproducible.
Options()errors now failexplicitly.
combinations.
composite modes.
processing buffer.
Added:
Utils_test.pyPrunedCoverage_test.pyImageEnhancement_validation_test.pyoutputs
TIDHE, RDFHE, NFLDICE, and BETCE are
validated against pixel-exact MATLAB hashes. SFCEF allows a maximum difference
of one gray level because of floating-point and FMA rounding.
Documentation
Updated
documentation.mdwith:NFLDICE, BETCE, and SFCEF
Updated
demos.mdwith separate mode 9examples for image enhancement and dithering.