flownet inference for a seq of images

examples/OpticalFlow/README.md

@@ -37,10 +37,13 @@ wget http://models.tensorpack.com/OpticalFlow/flownet2-c.npz
 
 ```bash
 python flownet2.py \
-	--left left.png --right right.png \
+	--images frame0.png frame1.png frame2.png
 	--load flownet2.npz --model flownet2
 ```
 
+This command will show predictions for all the consecutive pairs one by one.
+Press any key to visualize the next prediction.
+
 3. Evaluate AEE (Average Endpoing Error) on Sintel dataset:
 
 ```

examples/OpticalFlow/flownet2.py

@@ -14,15 +14,13 @@ import flownet_models as models
 from helper import Flow
 
 
-def apply(model, model_path, left, right, ground_truth=None):
-    left = cv2.imread(left)
-    right = cv2.imread(right)
-
+def apply(model, model_path, images, ground_truth=None):
+    left = cv2.imread(images[0])
     h, w = left.shape[:2]
     newh = (h // 64) * 64
     neww = (w // 64) * 64
     aug = imgaug.CenterCrop((newh, neww))
-    left, right = aug.augment(left), aug.augment(right)
+    left = aug.augment(left)
 
     predict_func = OfflinePredictor(PredictConfig(
         model=model(height=newh, width=neww),
@@ -30,6 +28,9 @@ def apply(model, model_path, left, right, ground_truth=None):
         input_names=['left', 'right'],
         output_names=['prediction']))
 
+    for right in images[1:]:
+        right = aug.augment(cv2.imread(right))
+
         left_input, right_input = [x.astype('float32').transpose(2, 0, 1)[None, ...]
                                    for x in [left, right]]
         output = predict_func(left_input, right_input)[0].transpose(0, 2, 3, 1)
@@ -45,6 +46,8 @@ def apply(model, model_path, left, right, ground_truth=None):
         cv2.imwrite('flow_prediction.png', img)
         cv2.waitKey(0)
 
+        left = right
+
 
 class SintelData(DataFlow):
 
@@ -118,8 +121,8 @@ if __name__ == '__main__':
     parser.add_argument('--load', help='path to the model', required=True)
     parser.add_argument('--model', help='model',
                         choices=['flownet2', 'flownet2-s', 'flownet2-c'], required=True)
-    parser.add_argument('--left', help='input')
-    parser.add_argument('--right', help='input')
+    parser.add_argument('--images', nargs="+",
+                        help='a list of equally-sized images. FlowNet will be applied to all consecutive pairs')
     parser.add_argument('--gt', help='path to ground truth flow')
     parser.add_argument('--sintel_path', help='path to sintel dataset')
     args = parser.parse_args()
@@ -131,4 +134,5 @@ if __name__ == '__main__':
     if args.sintel_path:
         inference(model, args.load, args.sintel_path)
     else:
-        apply(model, args.load, args.left, args.right, args.gt)
+        assert len(args.images) >= 2
+        apply(model, args.load, args.images, args.gt)