PlanckianJitter

Description

Applies Planckian Jitter to the input image, simulating color temperature variations in illumination.

    This transform adjusts the color of an image to mimic the effect of different color temperatures
    of light sources, based on Planck's law of black body radiation. It can simulate the appearance
    of an image under various lighting conditions, from warm (reddish) to cool (bluish) color casts.

    PlanckianJitter vs. ColorJitter:
    PlanckianJitter is fundamentally different from ColorJitter in its approach and use cases:
    1. Physics-based: PlanckianJitter is grounded in the physics of light, simulating real-world
       color temperature changes. ColorJitter applies arbitrary color adjustments.
    2. Natural effects: This transform produces color shifts that correspond to natural lighting
       variations, making it ideal for outdoor scene simulation or color constancy problems.
    3. Single parameter: Color changes are controlled by a single, physically meaningful parameter
       (color temperature), unlike ColorJitter's multiple abstract parameters.
    4. Correlated changes: Color shifts are correlated across channels in a way that mimics natural
       light, whereas ColorJitter can make independent channel adjustments.

    When to use PlanckianJitter:
    - Simulating different times of day or lighting conditions in outdoor scenes
    - Augmenting data for computer vision tasks that need to be robust to natural lighting changes
    - Preparing synthetic data to better match real-world lighting variations
    - Color constancy research or applications
    - When you need physically plausible color variations rather than arbitrary color changes

    The logic behind PlanckianJitter:
    As the color temperature increases:
    1. Lower temperatures (around 3000K) produce warm, reddish tones, simulating sunset or incandescent lighting.
    2. Mid-range temperatures (around 5500K) correspond to daylight.
    3. Higher temperatures (above 7000K) result in cool, bluish tones, similar to overcast sky or shade.
    This progression mimics the natural variation of sunlight throughout the day and in different weather conditions.

    Args:
        mode (Literal["blackbody", "cied"]): The mode of the transformation.
            - "blackbody": Simulates blackbody radiation color changes.
            - "cied": Uses the CIE D illuminant series for color temperature simulation.
            Default: "blackbody"

        temperature_limit (tuple[int, int] | None): The range of color temperatures (in Kelvin) to sample from.
            - For "blackbody" mode: Should be within [3000K, 15000K]. Default: (3000, 15000)
            - For "cied" mode: Should be within [4000K, 15000K]. Default: (4000, 15000)
            If None, the default ranges will be used based on the selected mode.
            Higher temperatures produce cooler (bluish) images, lower temperatures produce warmer (reddish) images.

        sampling_method (Literal["uniform", "gaussian"]): Method to sample the temperature.
            - "uniform": Samples uniformly across the specified range.
            - "gaussian": Samples from a Gaussian distribution centered at 6500K (approximate daylight).
            Default: "uniform"

        p (float): Probability of applying the transform. Default: 0.5

    Targets:
        image

    Image types:
        uint8, float32

    Number of channels:
        Any

    Note:
        - The transform preserves the overall brightness of the image while shifting its color.
        - The "blackbody" mode provides a wider range of color shifts, especially in the lower (warmer) temperatures.
        - The "cied" mode is based on standard illuminants and may provide more realistic daylight variations.
        - The Gaussian sampling method tends to produce more subtle variations, as it's centered around daylight.
        - Unlike ColorJitter, this transform ensures that color changes are physically plausible and correlated
          across channels, maintaining the natural appearance of the scene under different lighting conditions.

    Example:
        >>> import numpy as np
        >>> import albumentations as A
        >>> image = np.random.randint(0, 256, [100, 100, 3], dtype=np.uint8)
        >>> transform = A.PlanckianJitter(mode="blackbody",
        ...                               temperature_range=(3000, 9000),
        ...                               sampling_method="uniform",
        ...                               p=1.0)
        >>> result = transform(image=image)
        >>> jittered_image = result["image"]

    References:
        - Planck's law: https://en.wikipedia.org/wiki/Planck%27s_law
        - CIE Standard Illuminants: https://en.wikipedia.org/wiki/Standard_illuminant
        - Color temperature: https://en.wikipedia.org/wiki/Color_temperature
        - Implementation inspired by: https://github.com/TheZino/PlanckianJitter
    

Parameters

• mode: Literal['blackbody', 'cied'] (default: 'blackbody')
• temperature_limit: Annotated[tuple[int, int], AfterValidator(func=<function nondecreasing at 0x7c132ac54ae0>)] | None (default: null)
• sampling_method: Literal['uniform', 'gaussian'] (default: 'uniform')
• p: float (default: 0.5)

Targets

• Image