Fix salt and pepper

[ternaus]

Summary by Sourcery

Tests:

• Add tests for SaltAndPepper transform to verify correct application and expected behavior with different image types (uint8, float32, single-channel).

[sourcery-ai]

Reviewer's Guide by Sourcery

This pull request introduces a fix to the SaltAndPepper augmentation, addressing issues with incorrect noise application and ensuring proper handling of different image types. The changes include modifications to the mask generation logic and the application of noise to the image.

Sequence diagram for improved Salt and Pepper noise application

sequenceDiagram
    participant Transform as SaltAndPepper Transform
    participant Params as Parameter Generation
    participant Noise as Noise Application
    participant Image as Image Data

    Transform->>Image: Get image dimensions
    Image-->>Transform: Return height, width
    Transform->>Params: Generate noise parameters
    Params-->>Transform: Return total_amount and salt_ratio
    Transform->>Noise: Generate noise positions
    Noise->>Noise: Create salt and pepper masks
    Noise-->>Transform: Return masks
    Transform->>Image: Apply salt and pepper noise
    Note over Image: Handle multi-channel images
    Image-->>Transform: Return modified image

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Flow diagram for Salt and Pepper noise generation

flowchart TD
    A[Get image dimensions] --> B[Calculate area]
    B --> C[Generate noise parameters]
    C --> D[Calculate number of pixels]
    D --> E[Generate noise positions]
    E --> F[Create salt mask]
    E --> G[Create pepper mask]
    F & G --> H[Reshape masks to 2D]
    H --> I[Apply masks to image]
    I --> J{Is image 3D?}
    J -->|Yes| K[Expand masks to match channels]
    J -->|No| L[Apply directly]
    K & L --> M[Return modified image]

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File-Level Changes

Change	Details	Files
Fixed mask generation for salt and pepper noise.	Corrected the calculation of image dimensions to use the first two dimensions of the image shape. Modified the generation of random indices to use the total area of the image instead of the product of height and width. Reshaped the masks to 2D after generating the flat indices.	albumentations/augmentations/transforms.py
Ensured correct application of salt and pepper noise to the image.	Added a channel dimension to the masks if the image is 3D before applying the noise.	albumentations/augmentations/functional.py
Added comprehensive tests for the SaltAndPepper augmentation.	Added a test case for uint8 images to verify the correct number of noisy pixels and the salt vs pepper ratio. Added a test case for float32 images to ensure salt pixels are 1.0 and pepper pixels are 0.0. Added a test case for grayscale images to verify the shape is preserved and the noise values are correct.	tests/test_augmentations.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: 1 issue found
• 🟢 Security: all looks good
• 🟡 Testing: 1 issue found
• 🟢 Complexity: all looks good
• 🟢 Documentation: all looks good

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