Clean up mage resizing code.

This doesn’t change the functionality, other than
cleaning up the code to prepare for future changes
to support detection on different image sizes.

config.py

@@ -88,13 +88,16 @@ class Config(object):
     MINI_MASK_SHAPE = (56, 56)  # (height, width) of the mini-mask
 
     # Input image resizing
-    # Images are resized such that the smallest side is >= IMAGE_MIN_DIM and
-    # the longest side is <= IMAGE_MAX_DIM. In case both conditions can't
-    # be satisfied together the IMAGE_MAX_DIM is enforced.
+    # Images are resized such that the small side is IMAGE_MIN_DIM and
+    # the long side is <= IMAGE_MAX_DIM. If both conditions can't be
+    # satisfied at the same time then IMAGE_MAX_DIM is enforced.
+    # Resizing modes:
+    #     none: No resizing
+    #     square: Pad with zeros to make it a square (MAX_DIM, MAX_DIM)
+    # TODO: currently, only 'square' mode is supported
+    IMAGE_RESIZE_MODE = "square"
     IMAGE_MIN_DIM = 800
     IMAGE_MAX_DIM = 1024
-    # If True, pad images with zeros such that they're (max_dim by max_dim)
-    IMAGE_PADDING = True  # currently, the False option is not supported
 
     # Image mean (RGB)
     MEAN_PIXEL = np.array([123.7, 116.8, 103.9])

model.py

@@ -1198,7 +1198,7 @@ def load_image_gt(dataset, config, image_id, augment=False, augmentation=None,
         image,
         min_dim=config.IMAGE_MIN_DIM,
         max_dim=config.IMAGE_MAX_DIM,
-        padding=config.IMAGE_PADDING)
+        mode=config.IMAGE_RESIZE_MODE)
     mask = utils.resize_mask(mask, scale, padding)
 
     # Random horizontal flips.
@@ -2313,13 +2313,13 @@ class MaskRCNN():
         image_metas = []
         windows = []
         for image in images:
-            # Resize image to fit the model expected size
+            # Resize image
             # TODO: move resizing to mold_image()
             molded_image, window, scale, padding = utils.resize_image(
                 image,
                 min_dim=self.config.IMAGE_MIN_DIM,
                 max_dim=self.config.IMAGE_MAX_DIM,
-                padding=self.config.IMAGE_PADDING)
+                mode=self.config.IMAGE_RESIZE_MODE)
             molded_image = mold_image(molded_image, self.config)
             # Build image_meta
             image_meta = compose_image_meta(

utils.py

@@ -386,15 +386,17 @@ class Dataset(object):
         return mask, class_ids
 
 
-def resize_image(image, min_dim=None, max_dim=None, padding=False):
-    """
-    Resizes an image keeping the aspect ratio.
+def resize_image(image, min_dim=None, max_dim=None, mode="square"):
+    """Resizes an image keeping the aspect ratio unchanged.
 
     min_dim: if provided, resizes the image such that it's smaller
         dimension == min_dim
     max_dim: if provided, ensures that the image longest side doesn't
         exceed this value.
-    padding: If true, pads image with zeros so it's size is max_dim x max_dim
+    mode: Resizing mode.
+        none: No resizing. Return the image unchanged
+        square: Resize and pad with zeros to get a square image
+            of size [max_dim, max_dim]
 
     Returns:
     image: the resized image
@@ -409,6 +411,10 @@ def resize_image(image, min_dim=None, max_dim=None, padding=False):
     h, w = image.shape[:2]
     window = (0, 0, h, w)
     scale = 1
+    padding = [(0, 0), (0, 0), (0, 0)]
+
+    if mode == "none":
+        return image, window, scale, padding
 
     # Scale?
     if min_dim:
@@ -424,7 +430,7 @@ def resize_image(image, min_dim=None, max_dim=None, padding=False):
         image = scipy.misc.imresize(
             image, (round(h * scale), round(w * scale)))
     # Need padding?
-    if padding:
+    if mode == "square":
         # Get new height and width
         h, w = image.shape[:2]
         top_pad = (max_dim - h) // 2
@@ -434,6 +440,8 @@ def resize_image(image, min_dim=None, max_dim=None, padding=False):
         padding = [(top_pad, bottom_pad), (left_pad, right_pad), (0, 0)]
         image = np.pad(image, padding, mode='constant', constant_values=0)
         window = (top_pad, left_pad, h + top_pad, w + left_pad)
+    else:
+        raise Exception("Mode {} not supported".format(mode))
     return image, window, scale, padding