fix GoogleNetRandomCropResize interpolation

docs/tutorial/inference.md

@@ -12,92 +12,53 @@ There are two ways to do inference during training.
 
 2. If your inference follows the paradigm of:
 	"evaluate some tensors for each input, and aggregate the results in the end".
-	You can use the `InferenceRunner` interface with some `Inferencer**.
+	You can use the `InferenceRunner` interface with some `Inferencer`.
 	This will further support prefetch & data-parallel inference.
-	More details to come.
+	
+    Currently this lacks documentation, but you can refer to examples
+    that uses `InferenceRunner` or custom `Inferencer` to learn more.
 
 In both methods, your tower function will be called again, with `TowerContext.is_training==False`.
 You can use this predicate to choose a different code path in inference mode.
 
-## Inference After Training
 
-Tensorpack is a training interface -- __it doesn't care what happened after training__.
-You already have everything you need for inference or model diagnosis after
-training:
-1. The model (the graph): you've already written it yourself with TF symbolic functions.
-2. The trained parameters: tensorpack saves them in standard TF checkpoint format.
-
-### Step 1: build the model
-
-You can build a graph however you like, with pure TensorFlow. If your model is written with
-tensorpack's `ModelDesc`, you can also build it like this:
-
-```python
-a, b = tf.placeholder(...), tf.placeholder(...)
-# call ANY symbolic functions on a, b. e.g.:
-with TowerContext('', is_training=False):
-	model.build_graph(a, b)
-```
-
-```eval_rst
-.. note:: **Do not use metagraph for inference!**. 
-
-	Metagraph is the wrong abstraction for a "model". 
-	It stores the entire graph which contains not only the mathematical model, but also all the
-	training settings (queues, iterators, summaries, evaluations, multi-gpu replications).
-	Therefore it is usually wrong to import a training metagraph for inference.
+## Inference After Training: What Tensorpack Does
 
-    It's especially error-prone to load a metagraph on top of a non-empty graph.
-    The potential name conflicts between the current graph and the nodes in the
-    metagraph can lead to esoteric bugs or sometimes completely ruin the model.
-
-	It's also very common to change the graph for inference.
-	For example, you may need a different data layout for CPU inference,
-	or you may need placeholders in the inference graph (which may not even exist in
-	the training graph). However metagraph is not designed to be easily modified at all.
-
-	Due to the above reasons, to do inference, it's best to recreate a clean graph (and save it if needed) by yourself.
-```
-
-### Step 2: load the checkpoint
-
-You can just use `tf.train.Saver` for all the work.
-Alternatively, use tensorpack's `SaverRestore(path).init(tf.get_default_session())`
-
-
-Now, you've already built a graph for inference, and the checkpoint is loaded. 
-You can then apply any graph processing or use deployment tools TensorFlow supports.
-These are unrelated to tensorpack, and you'll need to read TF docs and __do it on your own__.
+Tensorpack provides some small tools to do the most basic types of inference for demo purposes.
+You can use them but
+__these approaches are often suboptimal and may fail__.
+They may often be inefficient or lack functionalities you need.
 
+If you need anything more complicated, please
+learn what TensorFlow can do, and __do it on your own__ because Tensorpack
+is a training interface and doesn't care what happened after training.
 
 ### OfflinePredictor
 
-Tensorpack provides one tool [OfflinePredictor](../modules/predict.html#tensorpack.predict.OfflinePredictor),
-to merge the above two steps together.
-It has simple functionailities to build the graph, load the checkpoint, and
-return a callable for you for simple prediction.
+Tensorpack provides  [OfflinePredictor](../modules/predict.html#tensorpack.predict.OfflinePredictor),
+for inference demo after training.
+It has functionailities to build the graph, load the checkpoint, and
+return a callable for you for simple prediction. Refer to its docs for details.
 
 OfflinePredictor is only for quick demo purposes.
 It runs inference on numpy arrays, therefore may not be the most efficient way.
 It also has very limited functionalities.
-If you need anything more complicated, please __do it on your own__ because Tensorpack
-doesn't care what happened after training.
 
-A simple explanation of how it works:
+A simple example of how it works:
 ```python
 pred_config = PredictConfig(
     session_init=get_model_loader(model_path),
     model=YourModel(),
-    input_names=['input1', 'input2'],
-    output_names=['output1', 'output2'])
+    input_names=['input1', 'input2'],  # tensor names in the graph, or name of the declared inputs
+    output_names=['output1', 'output2'])  # tensor names in the graph
 predictor = OfflinePredictor(pred_config)
-outputs = predictor(input1_array, input2_array)
+output1_array, output2_array = predictor(input1_array, input2_array)
 ```
 
-As mentioned before, you might want to use a different graph for inference, 
-e.g., use NHWC format, support base64-encoded images. 
-You can make these changes in the `model` or `tower_func` in your `PredictConfig`.
-The example in [examples/basic/export-model.py](../examples/basic/export-model.py) demonstrates such an altered inference graph.
+It's __common to use a different graph for inference__, 
+e.g., use NHWC format, support encoded image format, etc. 
+You can make these changes inside the `model` or `tower_func` in your `PredictConfig`.
+The example in [examples/basics/export-model.py](../examples/basics/export-model.py) demonstrates such an altered inference graph.
 
 ### Exporter
 
@@ -114,7 +75,7 @@ you can also save your models into other formats so it may be more friendly for
    This format contains both the graph and the variables. Refer to TensorFlow
    serving documentation on how to use it.
 
-2. Export to a frozen and pruned graph:
+2. Export to a frozen and pruned graph for TensorFlow's builtin tools such as TOCO:
 
    ```python
    ModelExporter(pred_config).export_compact('/path/to/compact_graph.pb', toco_compatible=True)
@@ -133,9 +94,71 @@ you can also save your models into other formats so it may be more friendly for
    tf.import_graph_def(graph_def)
    ```
 
-[examples/basic/export-model.py](../examples/basic/export-model.py) demonstrates the usage of such a frozen/pruned graph.
+[examples/basics/export-model.py](../examples/basics/export-model.py)
+demonstrates the usage of such a frozen/pruned graph.
+Again, you may often want to use a different graph for inference and you can
+do so by the arguments of `PredictConfig`.
+
+
+## Inference After Training: Do It Yourself
+
+Tensorpack is a training interface -- __it doesn't care what happened after training__.
+It already provides everything you need for inference or model diagnosis after
+training:
+
+1. The model (the graph): you've already written it yourself with TF symbolic functions.
+   Nothing about it is related to the tensorpack interface.
+   If you use tensorpack layers, they are mainly just wrappers around `tf.layers`.
+
+2. The trained parameters: tensorpack saves them in standard TF checkpoint format.
+   Nothing about it is related to tensorpack.
+
+With the model and the weights, you can do inference with whatever approaches
+TensorFlow supports. Usually it involves the following steps:
+
+### Step 1: build the model (graph)
+
+You can build a graph however you like, with pure TensorFlow. If your model is written with
+tensorpack's `ModelDesc`, you can also build it like this:
+
+```python
+a, b = tf.placeholder(...), tf.placeholder(...)
+# call ANY symbolic functions on a, b. e.g.:
+with TowerContext('', is_training=False):
+	model.build_graph(a, b)
+```
+
+```eval_rst
+.. note:: **Do not use metagraph for inference!**. 
+
+	Metagraph is the wrong abstraction for a "model". 
+	It stores the entire graph which contains not only the mathematical model, but also all the
+	training settings (queues, iterators, summaries, evaluations, multi-gpu replications).
+	Therefore it is usually wrong to import a training metagraph for inference.
+
+    It's especially error-prone to load a metagraph on top of a non-empty graph.
+    The potential name conflicts between the current graph and the nodes in the
+    metagraph can lead to esoteric bugs or sometimes completely ruin the model.
+
+	It's also very common to change the graph for inference.
+	For example, you may need a different data layout for CPU inference,
+	or you may need placeholders in the inference graph (which may not even exist in
+	the training graph). However metagraph is not designed to be easily modified at all.
+
+	Due to the above reasons, to do inference, it's best to recreate a clean graph (and save it if needed) by yourself.
+```
+
+### Step 2: load the checkpoint
+
+You can just use `tf.train.Saver` for all the work.
+Alternatively, use tensorpack's `SaverRestore(path).init(tf.get_default_session())`
+
+Now, you've already built a graph for inference, and the checkpoint is loaded. 
+You may now:
+
+1. use `sess.run` to do inference
+2. save the grpah to some formats for further processing
+3. apply graph transformation for efficient inference
 
-Note that these steps are not the optimal way for inference. They may very likely
-produce an inefficent graph.
-To do efficient inference, understand what TensorFlow can do and do it on your
-own, because inference after training is unrelated to tensorpack.
+These steps are unrelated to tensorpack, and you'll need to learn TensorFlow and
+do it yourself.

tensorpack/dataflow/imgaug/crop.py

@@ -94,11 +94,11 @@ class GoogleNetRandomCropAndResize(ImageAugmentor):
 
     It attempts to crop a random rectangle with 8%~100% area of the original image,
     and keep the aspect ratio between 3/4 to 4/3. Then it resize this crop to the target shape.
-    If such crop cannot be found in 10 iterations, it will to a ResizeShortestEdge + CenterCrop.
+    If such crop cannot be found in 10 iterations, it will do a ResizeShortestEdge + CenterCrop.
     """
     def __init__(self, crop_area_fraction=(0.08, 1.),
                  aspect_ratio_range=(0.75, 1.333),
-                 target_shape=224, interp=cv2.INTER_LINEAR):
+                 target_shape=224, interp=cv2.INTER_CUBIC):
         """
         Args:
             crop_area_fraction (tuple(float)): Defaults to crop 8%-100% area.
@@ -123,7 +123,7 @@ class GoogleNetRandomCropAndResize(ImageAugmentor):
                 out = img[y1:y1 + hh, x1:x1 + ww]
                 out = cv2.resize(out, (self.target_shape, self.target_shape), interpolation=self.interp)
                 return out
-        out = ResizeShortestEdge(self.target_shape, interp=cv2.INTER_CUBIC).augment(img)
+        out = ResizeShortestEdge(self.target_shape, interp=self.interp).augment(img)
         out = CenterCrop(self.target_shape).augment(out)
         return out