Albumentations

----|---------------|----------| | Pixel-level | BrightnessContrast, Gamma, HueSaturationValue, CLAHE, Blur, GaussNoise, ISONoise, RGBShift, ChannelShuffle, ToGray, Solarize, Posterize, Equalize, ColorJitter | Color/lighting variation | | Spatial-level | RandomCrop, CenterCrop, Resize, Rotate, Flip, ShiftScaleRotate, Affine, ElasticTransform, GridDistortion, OpticalDistortion, Perspective, PiecewiseAffine | Geometric variation | | Weather | RandomRain, RandomSnow, RandomFog, RandomSunFlare | Adverse conditions | | Advanced | CoarseDropout, Cutout, MixUp, Mosaic | Regularization, domain gap | | Special | CLAHE, Emboss, Sharpen, Superpixels, FDA, HistogramMatching, PixelDistributionAdaptation | Medical, domain adaptation |

5. Probability and OneOf Composition

# OneOf: apply exactly one transform from a list
transform = A.Compose([
    A.OneOf([
        A.RandomBrightnessContrast(p=1.0),
        A.RandomGamma(p=1.0),
        A.HueSaturationValue(p=1.0),
    ], p=0.8),
    A.HorizontalFlip(p=0.5),
])

# SomeOf: apply up to N transforms from a list
transform = A.Compose([
    A.SomeOf([
        A.GaussNoise(p=1.0),
        A.ISONoise(p=1.0),
        A.MultiplicativeNoise(p=1.0),
    ], n=2, replace=False, p=0.5),
])

# Per-transform probability
transform = A.Compose([
    A.RandomCrop(256, 256, p=1.0),       # Always applied
    A.HorizontalFlip(p=0.5),             # 50% chance
    A.RandomBrightnessContrast(p=0.2),    # 20% chance
])

6. Bounding Box Formats

# Supported formats:
# pascal_voc: [x_min, y_min, x_max, y_max] (pixels)
# albumentations: normalized [x_center, y_center, width, height]
# coco: [x_min, y_min, width, height] (pixels)
# yolo: normalized [x_center, y_center, width, height]

transform = A.Compose([
    A.HorizontalFlip(p=0.5),
], bbox_params=A.BboxParams(
    format="coco",
    min_visibility=0.3,      # Drop bboxes <30% visible after transform
    label_fields=["class_labels", "class_ids"],  # Extra fields to transform
))

7. Replay Mode (Reproducible Augmentations)

Apply identical augmentation parameters to multiple images:

transform = A.Compose([
    A.RandomCrop(256, 256),
    A.HorizontalFlip(p=0.5),
    A.RandomBrightnessContrast(p=0.5),
])

# Apply to first image, get replay params
data = transform(image=image1, mask=mask1)
replay_params = data["replay"]

# Reapply IDENTICAL transforms to second image
data2 = A.ReplayCompose.replay(replay_params, image=image2, mask=mask2)

8. Serialization (Save/Load Pipelines)

import albumentations as A

transform = A.Compose([
    A.RandomCrop(256, 256),
    A.HorizontalFlip(p=0.5),
    A.Normalize(mean=[0.485, 0.456, 0.406], std=[0.229, 0.224, 0.225]),
])

# Save to YAML/JSON
A.save(transform, "augmentation_pipeline.yaml")
A.save(transform, "augmentation_pipeline.json")

# Load back
loaded = A.load("augmentation_pipeline.yaml")

9. PyTorch Integration

import albumentations as A
from albumentations.pytorch import ToTensorV2

train_transform = A.Compose([
    A.RandomResizedCrop(224, 224),
    A.HorizontalFlip(p=0.5),
    A.ColorJitter(brightness=0.2, contrast=0.2, p=0.5),
    A.Normalize(mean=[0.485, 0.456, 0.406], std=[0.229, 0.224, 0.225]),
    ToTensorV2(),  # Convert HWC numpy → CHW tensor
])

val_transform = A.Compose([
    A.Resize(256, 256),
    A.CenterCrop(224, 224),
    A.Normalize(mean=[0.485, 0.456, 0.406], std=[0.229, 0.224, 0.225]),
    ToTensorV2(),
])

# In PyTorch Dataset:
class MyDataset(Dataset):
    def __getitem__(self, idx):
        image = cv2.imread(self.images[idx])
        image = cv2.cvtColor(image, cv2.COLOR_BGR2RGB)

        if self.transform:
            augmented = self.transform(image=image)
            image = augmented["image"]

        return image, self.labels[idx]

10. Advanced Transforms

MixUp (alpha blending two images):

transform = A.Compose([
    A.MixUp(reference_data=reference_dataset, alpha=0.4, p=0.5),
    A.HorizontalFlip(p=0.5),
])

CoarseDropout (Cutout regularization):

transform = A.Compose([
    A.CoarseDropout(max_holes=8, max_height=32, max_width=32, p=0.5),
])

FDA (Fourier Domain Adaptation):

# Swap low-frequency components between source and target domain images
transform = A.Compose([
    A.FDA(reference_images=target_domain_images, beta_limit=0.1, p=0.5),
])

Key Patterns

1. Always convert BGR to RGB when using OpenCV — Albumentations works in RGB
2. Use A.Compose with probabilities to control augmentation strength
3. Use OneOf for mutually exclusive transforms (e.g., pick one blur method)
4. Normalize at the END of the pipeline — after all other transforms
5. Use ToTensorV2() for seamless PyTorch conversion
6. Replay mode for consistent augmentations across image pairs (stereo, temporal)
7. Save/Load pipelines for reproducibility across training runs
8. Albumentations is MIT-licensed but unmaintained — consider AlbumentationsX for active projects

References

• Albumentations Documentation
• Transform Gallery — interactive demo
• Benchmark Results
• Examples Gallery
• AlbumentationsX (successor)