src/preprocessing/augmentation.py

"""
Data augmentation utilities for the Emotion Recognition System.
"""
import numpy as np
from typing import Tuple, Optional
from tensorflow.keras.preprocessing.image import ImageDataGenerator

import sys
from pathlib import Path
sys.path.append(str(Path(__file__).parent.parent.parent))
from src.config import AUGMENTATION_CONFIG


def get_augmentation_generator(
    rotation_range: int = AUGMENTATION_CONFIG["rotation_range"],
    width_shift_range: float = AUGMENTATION_CONFIG["width_shift_range"],
    height_shift_range: float = AUGMENTATION_CONFIG["height_shift_range"],
    horizontal_flip: bool = AUGMENTATION_CONFIG["horizontal_flip"],
    zoom_range: float = AUGMENTATION_CONFIG["zoom_range"],
    brightness_range: Tuple[float, float] = AUGMENTATION_CONFIG["brightness_range"],
    fill_mode: str = AUGMENTATION_CONFIG["fill_mode"],
    rescale: float = 1./255
) -> ImageDataGenerator:
    """
    Create an ImageDataGenerator with augmentation settings.
    
    Args:
        rotation_range: Degree range for random rotations
        width_shift_range: Fraction for horizontal shifts
        height_shift_range: Fraction for vertical shifts
        horizontal_flip: Whether to randomly flip horizontally
        zoom_range: Range for random zoom
        brightness_range: Range for brightness adjustment
        fill_mode: Points outside boundaries fill method
        rescale: Rescaling factor
        
    Returns:
        Configured ImageDataGenerator
    """
    return ImageDataGenerator(
        rescale=rescale,
        rotation_range=rotation_range,
        width_shift_range=width_shift_range,
        height_shift_range=height_shift_range,
        horizontal_flip=horizontal_flip,
        zoom_range=zoom_range,
        brightness_range=brightness_range,
        fill_mode=fill_mode
    )


def augment_image(
    image: np.ndarray,
    num_augmentations: int = 5,
    generator: Optional[ImageDataGenerator] = None
) -> np.ndarray:
    """
    Generate augmented versions of a single image.
    
    Args:
        image: Input image array of shape (height, width, channels)
        num_augmentations: Number of augmented images to generate
        generator: Optional ImageDataGenerator, creates default if None
        
    Returns:
        Array of augmented images of shape (num_augmentations, height, width, channels)
    """
    if generator is None:
        generator = get_augmentation_generator(rescale=1.0)  # No rescale for single images
    
    # Reshape for generator (needs batch dimension)
    image_batch = np.expand_dims(image, axis=0)
    
    # Generate augmented images
    augmented_images = []
    aug_iter = generator.flow(image_batch, batch_size=1)
    
    for _ in range(num_augmentations):
        augmented = next(aug_iter)[0]
        augmented_images.append(augmented)
    
    return np.array(augmented_images)


def create_balanced_augmentation(
    images: np.ndarray,
    labels: np.ndarray,
    target_samples_per_class: int
) -> Tuple[np.ndarray, np.ndarray]:
    """
    Create a balanced dataset through augmentation of minority classes.
    
    Args:
        images: Array of images
        labels: Array of one-hot encoded labels
        target_samples_per_class: Target number of samples per class
        
    Returns:
        Tuple of (augmented_images, augmented_labels)
    """
    generator = get_augmentation_generator(rescale=1.0)
    
    # Convert one-hot to class indices
    class_indices = np.argmax(labels, axis=1)
    unique_classes = np.unique(class_indices)
    
    augmented_images = []
    augmented_labels = []
    
    for class_idx in unique_classes:
        # Get images of this class
        class_mask = class_indices == class_idx
        class_images = images[class_mask]
        class_labels = labels[class_mask]
        
        current_count = len(class_images)
        
        # Add original images
        augmented_images.extend(class_images)
        augmented_labels.extend(class_labels)
        
        # Generate more if needed
        if current_count < target_samples_per_class:
            needed = target_samples_per_class - current_count
            
            for i in range(needed):
                # Select random image from class
                idx = np.random.randint(0, current_count)
                original = class_images[idx]
                
                # Generate one augmented version
                aug = augment_image(original, num_augmentations=1, generator=generator)[0]
                augmented_images.append(aug)
                augmented_labels.append(class_labels[idx])
    
    return np.array(augmented_images), np.array(augmented_labels)


def get_augmentation_preview(
    image: np.ndarray,
    num_samples: int = 9
) -> np.ndarray:
    """
    Generate a preview of augmentations for visualization.
    
    Args:
        image: Original image
        num_samples: Number of augmented samples to generate
        
    Returns:
        Array including original + augmented images
    """
    augmented = augment_image(image, num_augmentations=num_samples - 1)
    
    # Add original as first image
    original = np.expand_dims(image, axis=0)
    return np.concatenate([original, augmented], axis=0)