Random Resized Crop

keras_cv/layers/__init__.py

@@ -52,6 +52,7 @@
 from keras_cv.layers.preprocessing.random_gaussian_blur import RandomGaussianBlur
 from keras_cv.layers.preprocessing.random_hue import RandomHue
 from keras_cv.layers.preprocessing.random_jpeg_quality import RandomJpegQuality
+from keras_cv.layers.preprocessing.random_resized_crop import RandomResizedCrop
 from keras_cv.layers.preprocessing.random_saturation import RandomSaturation
 from keras_cv.layers.preprocessing.random_sharpness import RandomSharpness
 from keras_cv.layers.preprocessing.random_shear import RandomShear

keras_cv/layers/preprocessing/__init__.py

@@ -56,6 +56,7 @@
 from keras_cv.layers.preprocessing.random_gaussian_blur import RandomGaussianBlur
 from keras_cv.layers.preprocessing.random_hue import RandomHue
 from keras_cv.layers.preprocessing.random_jpeg_quality import RandomJpegQuality
+from keras_cv.layers.preprocessing.random_resized_crop import RandomResizedCrop
 from keras_cv.layers.preprocessing.random_saturation import RandomSaturation
 from keras_cv.layers.preprocessing.random_sharpness import RandomSharpness
 from keras_cv.layers.preprocessing.random_shear import RandomShear

keras_cv/layers/preprocessing/random_resized_crop.py

@@ -0,0 +1,184 @@
+# Copyright 2022 The KerasCV Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+import warnings
+
+import tensorflow as tf
+
+from keras_cv import core
+from keras_cv.layers.preprocessing.base_image_augmentation_layer import (
+    BaseImageAugmentationLayer, )
+from keras_cv.utils import preprocessing
+
+
+@tf.keras.utils.register_keras_serializable(package="keras_cv")
+class RandomResizedCrop(BaseImageAugmentationLayer):
+    """Randomly crops a part of an image and resizes it to provided size.
+
+    This implementation takes an intuitive approach, where we crop the images to a
+    random height and width, and then resize them. To do this, we first sample a
+    random value for area using `area_factor` and a value for aspect ratio using
+    `aspect_ratio_factor`. Further we get the new height and width by
+    dividing and multiplying the old height and width by the random area
+    respectively. We then sample offsets for height and width and clip them such
+    that the cropped area does not exceed image boundaries. Finally we do the
+    actual cropping operation and resize the image to `target_size`.
+
+    Args:
+        target_size: A tuple of two integers used as the target size to ultimately crop
+            images to.
+        area_factor: (Optional) A tuple of two floats, a single float or
+            `keras_cv.FactorSampler`. The ratio of area of the cropped part to
+            that of original image is sampled using this factor. Represents the
+            lower and upper bounds for the area relative to the original image
+            of the cropped image before resizing it to `target_size`.
+            `target_size`.  Defaults to (0.08, 1.0).
+        aspect_ratio_factor: (Optional) A tuple of two floats, a single float or
+            `keras_cv.FactorSampler`. Aspect ratio means the ratio of width to
+            height of the cropped image. In the context of this layer, the aspect ratio
+            sampled represents a value to distort the aspect ratio by.
+            Represents the lower and upper bound for the aspect ratio of the
+            cropped image before resizing it to `target_size`. Defaults to
+            (3./4., 4./3.).
+        interpolation: (Optional) A string specifying the sampling method for
+            resizing. Defaults to "bilinear".
+        seed: (Optional) Used to create a random seed. Defaults to None.
+    """
+    def __init__(
+        self,
+        target_size,
+        area_factor=(0.08, 1.0),
+        aspect_ratio_factor=(3. / 4., 4. / 3.),
+        interpolation="bilinear",
+        seed=None,
+        **kwargs,
+    ):
+        super().__init__(seed=seed, **kwargs)
+
+        self.target_size = target_size
+
+        aspect_ratio_factor = aspect_ratio_factor or (3. / 4., 4. / 3.)
+        if isinstance(aspect_ratio_factor, tuple):
+            min_aspect_ratio = min(aspect_ratio_factor)
+            max_aspect_ratio = max(aspect_ratio_factor)
+        elif isinstance(aspect_ratio_factor, core.FactorSampler):
+            pass
+        else:
+            raise ValueError(
+                "Expected `aspect_ratio` to be tuple or FactorSampler. Received "
+                f"RandomResizedCrop(aspect_ratio_factor={aspect_ratio_factor})."
+            )
+
+        self.aspect_ratio_factor = preprocessing.parse_factor(
+            aspect_ratio_factor,
+            min_value=min_aspect_ratio,
+            max_value=max_aspect_ratio,
+            param_name="aspect_ratio_factor",
+            seed=seed,
+        )
+        self.area_factor = preprocessing.parse_factor(
+            area_factor,
+            max_value=1.0,
+            param_name="area_factor",
+            seed=seed,
+        )
+
+        self.interpolation = interpolation
+        self.seed = seed
+
+        if area_factor == 0.0 and aspect_ratio_factor == 0.0:
+            warnings.warn(
+                "RandomResizedCrop received both `area_factor=0.0` and "
+                "`aspect_ratio_factor=0.0`. As a result, the layer will perform no "
+                "augmentation.")
+
+    def get_random_transformation(self,
+                                  image=None,
+                                  label=None,
+                                  bounding_box=None,
+                                  **kwargs):
+        area_factor = self.area_factor()
+        aspect_ratio = self.aspect_ratio_factor()
+
+        new_height = tf.clip_by_value(
+            tf.sqrt(area_factor / aspect_ratio), 0.0,
+            1.0)  # to avoid unwanted/unintuitive effects
+        new_width = tf.clip_by_value(tf.sqrt(area_factor * aspect_ratio), 0.0,
+                                     1.0)
+
+        height_offset = self._random_generator.random_uniform(
+            (),
+            minval=tf.minimum(0.0, 1.0 - new_height),
+            maxval=tf.maximum(0.0, 1.0 - new_height),
+            dtype=tf.float32,
+        )
+
+        width_offset = self._random_generator.random_uniform(
+            (),
+            minval=tf.minimum(0.0, 1.0 - new_width),
+            maxval=tf.maximum(0.0, 1.0 - new_width),
+            dtype=tf.float32,
+        )
+
+        y1 = height_offset
+        y2 = height_offset + new_height
+        x1 = width_offset
+        x2 = width_offset + new_width
+
+        return [[y1, x1, y2, x2]]
+
+    def call(self, inputs, training=True):
+
+        if training:
+            return super().call(inputs, training)
+        else:
+            inputs = self._ensure_inputs_are_compute_dtype(inputs)
+            inputs, is_dict, use_targets = self._format_inputs(inputs)
+            output = inputs
+            # self._resize() returns valid results for both batched and
+            # unbatched
+            output["images"] = self._resize(inputs["images"])
+            return self._format_output(output, is_dict, use_targets)
+
+    def augment_image(self, image, transformation, **kwargs):
+        image = tf.expand_dims(image, axis=0)
+        boxes = transformation
+
+        # See bit.ly/tf_crop_resize for more details
+        augmented_image = tf.image.crop_and_resize(
+            image,  # image shape: [B, H, W, C]
+            boxes,  # boxes: (1, 4) in this case; represents area
+            # to be cropped from the original image
+            [0],  # box_indices: maps boxes to images along batch axis
+            # [0] since there is only one image
+            self.target_size,  # output size
+        )
+
+        return tf.squeeze(augmented_image, axis=0)
+
+    def _resize(self, image):
+        outputs = tf.keras.preprocessing.image.smart_resize(
+            image, self.target_size)
+        # smart_resize will always output float32, so we need to re-cast.
+        return tf.cast(outputs, self.compute_dtype)
+
+    def get_config(self):
+        config = super().get_config()
+        config.update({
+            "target_size": self.target_size,
+            "area_factor": self.area_factor,
+            "aspect_ratio_factor": self.aspect_ratio_factor,
+            "interpolation": self.interpolation,
+            "seed": self.seed,
+        })
+        return config

keras_cv/layers/preprocessing/random_resized_crop_test.py

@@ -0,0 +1,62 @@
+# Copyright 2022 The KerasCV Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+import tensorflow as tf
+
+from keras_cv.layers import preprocessing
+
+
+class RandomResizedCropTest(tf.test.TestCase):
+    height, width = 300, 300
+    batch_size = 4
+    target_size = (224, 224)
+    def test_train_augments_image(self):
+        # Checks if original and augmented images are different
+
+        input_image_shape = (self.batch_size, self.height, self.width, 3)
+        image = tf.random.uniform(shape=input_image_shape)
+
+        layer = preprocessing.RandomResizedCrop(
+            target_size=self.target_size, area_factor=(0.08, 1.0)
+        )
+        output = layer(image, training=True)
+
+        input_image_resized = tf.image.resize(image, self.target_size)
+
+        self.assertNotAllClose(output, input_image_resized)
+
+    def test_grayscale(self):
+        input_image_shape = (self.batch_size, self.height, self.width, 1)
+        image = tf.random.uniform(shape=input_image_shape)
+
+        layer = preprocessing.RandomResizedCrop(target_size=self.target_size,
+                                                area_factor=(0.8, 1.0))
+        output = layer(image, training=True)
+
+        input_image_resized = tf.image.resize(image, self.target_size)
+
+        self.assertAllEqual(output.shape, (4, 224, 224, 1))
+        self.assertNotAllClose(output, input_image_resized)
+
+    def test_preserves_image(self):
+        image_shape = (self.batch_size, self.height, self.width, 3)
+        image = tf.random.uniform(shape=image_shape)
+
+        layer = preprocessing.RandomResizedCrop(
+            target_size=self.target_size, area_factor=(0.8, 1.0)
+        )
+
+        input_resized = tf.image.resize(image, self.target_size)
+        output = layer(image, training=False)
+
+        self.assertAllClose(output, input_resized)

keras_cv/layers/serialization_test.py

@@ -117,6 +117,17 @@ class SerializationTest(tf.test.TestCase, parameterized.TestCase):
                 "seed": 1,
             },
         ),
+        (
+            "RandomResizedCrop",
+            preprocessing.RandomResizedCrop,
+            {
+                "target_size": (224, 224),
+                "area_factor": (0.08, 1.0),
+                "aspect_ratio_factor": (3.0 / 4.0, 4.0 / 3.0),
+                "interpolation": "bilinear",
+                "seed": 1,
+            },
+        ),
         (
             "DropBlock2D",
             regularization.DropBlock2D,