Fix pixel dropout

[ternaus]

Fixes: #2279

Summary by Sourcery

Fix bugs related to the PixelDropout transform, including incorrect drop value handling for multi-channel images and per-channel dropout with sequence values.

Bug Fixes:

• Fix incorrect drop value handling for multi-channel images in PixelDropout.
• Fix per-channel dropout with sequence values in PixelDropout.

Tests:

• Add tests for PixelDropout to verify correct drop value handling and per-channel dropout behavior.

[sourcery-ai]

Reviewer's Guide by Sourcery

This pull request addresses an issue in the PixelDropout augmentation where the drop_value parameter was not being correctly applied when per_channel was set to True. The changes ensure that the drop_value is correctly applied per channel, and adds tests to verify the fix.

Class diagram for updated PixelDropout transform

classDiagram
    class PixelDropout {
        +dropout_prob: float
        +per_channel: bool
        +drop_value: ColorType
        +mask_drop_value: ColorType
        +p: float
        +__init__(dropout_prob: float, per_channel: bool, drop_value: ColorType, mask_drop_value: ColorType, p: float)
        +apply(img: ndarray, drop_mask: ndarray, drop_values: ndarray): ndarray
    }
    class DualTransform {
        <<parent>>
    }
    DualTransform <|-- PixelDropout
    note for PixelDropout "Changed drop_value and mask_drop_value
type from ScaleFloatType to ColorType
Removed per_channel restriction"

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Flow diagram for pixel dropout process

flowchart TD
    A[Input Image] --> B{Per Channel?}
    B -->|Yes| C[Apply dropout per channel]
    B -->|No| D[Apply dropout globally]
    C --> E[Apply drop values per channel]
    D --> F[Apply single drop value]
    E --> G[Output Image]
    F --> G

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File-Level Changes

Change	Details	Files
Fixed the application of drop_value in PixelDropout when per_channel is True.	Modified PixelDropout to correctly apply drop_value per channel when per_channel is True. Updated prepare_drop_values to handle sequence drop_value for multichannel images. Removed the restriction on mask_drop_value when per_channel is True.	albumentations/augmentations/transforms.py albumentations/augmentations/functional.py
Added new tests to verify the fix for PixelDropout.	Added tests for different drop_value types (None, single value, sequence) when per_channel is False. Added tests for drop_value with per_channel set to True, including single and sequence values. Added a functional test to verify pixel_dropout with sequence values and per_channel=True.	tests/test_augmentations.py tests/functional/test_functional.py

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[sourcery-ai]

Hey @ternaus - I've reviewed your changes and they look great!

Here's what I looked at during the review

• 🟢 General issues: all looks good
• 🟢 Security: all looks good
• 🟡 Testing: 3 issues found
• 🟢 Complexity: all looks good
• 🟢 Documentation: all looks good

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.85%. Comparing base (b1a79c2) to head (622fc88).
Report is 380 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##           main    #2280       +/-   ##
=========================================
+ Coverage      0   89.85%   +89.85%     
=========================================
  Files         0       50       +50     
  Lines         0     8818     +8818     
=========================================
+ Hits          0     7923     +7923     
- Misses        0      895      +895     

Flag	Coverage Δ
ubuntu-py3.12	89.85% <100.00%> (?)

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