Document object detector augmentations (#776)

Co-authored-by: Ethan Harris <[email protected]>

docs/source/reference/object_detection.rst

@@ -73,3 +73,35 @@ To view configuration options and options for running the object detector with y
 .. code-block:: bash
 
     flash object_detection --help
+
+------
+
+**********************
+Custom Transformations
+**********************
+
+Flash automatically applies some default image / mask transformations and augmentations, but you may wish to customize these for your own use case.
+The base :class:`~flash.core.data.process.Preprocess` defines 7 hooks for different stages in the data loading pipeline.
+For object-detection tasks, you can leverage the transformations from `Albumentations <https://github.com/albumentations-team/albumentations>`__ with the :class:`~flash.core.integrations.icevision.transforms.IceVisionTransformAdapter`.
+
+.. code-block:: python
+
+    import albumentations as alb
+    from icevision.tfms import A
+
+    from flash.core.integrations.icevision.transforms import IceVisionTransformAdapter
+    from flash.image import ObjectDetectionData
+
+    train_transform = {
+        "pre_tensor_transform": transforms.IceVisionTransformAdapter(
+            [*A.resize_and_pad(128), A.Normalize(), A.Flip(0.4), alb.RandomBrightnessContrast()]
+        )
+    }
+
+    datamodule = ObjectDetectionData.from_coco(
+        train_folder="data/coco128/images/train2017/",
+        train_ann_file="data/coco128/annotations/instances_train2017.json",
+        val_split=0.1,
+        image_size=128,
+        train_transform=train_transform,
+    )

flash/core/integrations/icevision/transforms.py

@@ -196,7 +196,13 @@ def from_icevision_predictions(predictions: List["Prediction"]):
 
 
 class IceVisionTransformAdapter(nn.Module):
-    def __init__(self, transform):
+    """
+    Args:
+        transform: list of transformation functions to apply
+
+    """
+
+    def __init__(self, transform: List[Callable]):
         super().__init__()
         self.transform = A.Adapter(transform)
 

flash/core/utilities/imports.py

@@ -17,7 +17,6 @@
 import types
 from importlib.util import find_spec
 from typing import List, Union
-from warnings import warn
 
 from pkg_resources import DistributionNotFound
 
@@ -107,19 +106,8 @@ def _compare_version(package: str, op, version) -> bool:
     from PIL import Image  # noqa: F401
 else:
 
-    class MetaImage(type):
-        def __init__(cls, name, bases, dct):
-            super().__init__(name, bases, dct)
-
-            cls._Image = None
-
-        @property
-        def Image(cls):
-            warn("Mock object called due to missing PIL library. Please use \"pip install 'lightning-flash[image]'\".")
-            return cls._Image
-
-    class Image(metaclass=MetaImage):
-        pass
+    class Image:
+        Image = object
 
 
 if Version: