Fix an RGB conversion issue. (jacobgil#89)

* Fixes an RGB conversion issue.

1. The input image is RGB so use_rgb must be set to True in ``show_cam_on_image``
2. The returned cam_image is RGB encoded whereas cv2.imwrite requires BGR. Switch encoding of cam_image from RGB to BGR prior to writing.

* Change BGR2RGB -> RGB2BGR

cam.py

@@ -99,7 +99,10 @@ def get_args():
     # Here grayscale_cam has only one image in the batch
     grayscale_cam = grayscale_cam[0, :]
 
-    cam_image = show_cam_on_image(rgb_img, grayscale_cam)
+    cam_image = show_cam_on_image(rgb_img, grayscale_cam, use_rgb=True)
+
+    # cam_image is RGB encoded whereas "cv2.imwrite" requires BGR encoding.
+    cam_image = cv2.cvtColor(cam_image, cv2.COLOR_RGB2BGR)
 
     gb_model = GuidedBackpropReLUModel(model=model, use_cuda=args.use_cuda)
     gb = gb_model(input_tensor, target_category=target_category)