add yolo_box (#1608)

* add yolo_box and add unittest of yolo_box.

* update comment

* update sample code, call op in ppdet

ppdet/modeling/ops.py

@@ -32,7 +32,7 @@ __all__ = [
     #'generate_proposals',
     'iou_similarity',
     #'box_coder',
-    #'yolo_box',
+    'yolo_box',
     #'multiclass_nms',
     'distribute_fpn_proposals',
     'collect_fpn_proposals',
@@ -534,3 +534,138 @@ def distribute_fpn_proposals(fpn_rois,
     if rois_num is not None:
         return multi_rois, restore_ind, rois_num_per_level
     return multi_rois, restore_ind
+
+
+def yolo_box(
+        x,
+        origin_shape,
+        anchors,
+        class_num,
+        conf_thresh,
+        downsample_ratio,
+        clip_bbox=True,
+        scale_x_y=1.,
+        name=None, ):
+    """
+
+    This operator generates YOLO detection boxes from output of YOLOv3 network.
+     
+     The output of previous network is in shape [N, C, H, W], while H and W
+     should be the same, H and W specify the grid size, each grid point predict
+     given number boxes, this given number, which following will be represented as S,
+     is specified by the number of anchors. In the second dimension(the channel
+     dimension), C should be equal to S * (5 + class_num), class_num is the object
+     category number of source dataset(such as 80 in coco dataset), so the
+     second(channel) dimension, apart from 4 box location coordinates x, y, w, h,
+     also includes confidence score of the box and class one-hot key of each anchor
+     box.
+     Assume the 4 location coordinates are :math:`t_x, t_y, t_w, t_h`, the box
+     predictions should be as follows:
+     $$
+     b_x = \\sigma(t_x) + c_x
+     $$
+     $$
+     b_y = \\sigma(t_y) + c_y
+     $$
+     $$
+     b_w = p_w e^{t_w}
+     $$
+     $$
+     b_h = p_h e^{t_h}
+     $$
+     in the equation above, :math:`c_x, c_y` is the left top corner of current grid
+     and :math:`p_w, p_h` is specified by anchors.
+     The logistic regression value of the 5th channel of each anchor prediction boxes
+     represents the confidence score of each prediction box, and the logistic
+     regression value of the last :attr:`class_num` channels of each anchor prediction
+     boxes represents the classifcation scores. Boxes with confidence scores less than
+     :attr:`conf_thresh` should be ignored, and box final scores is the product of
+     confidence scores and classification scores.
+     $$
+     score_{pred} = score_{conf} * score_{class}
+     $$
+
+    Args:
+        x (Tensor): The input tensor of YoloBox operator is a 4-D tensor with shape of [N, C, H, W].
+                    The second dimension(C) stores box locations, confidence score and
+                    classification one-hot keys of each anchor box. Generally, X should be the output of YOLOv3 network.
+                    The data type is float32 or float64.
+        origin_shape (Tensor): The image size tensor of YoloBox operator, This is a 2-D tensor with shape of [N, 2].
+                    This tensor holds height and width of each input image used for resizing output box in input image
+                    scale. The data type is int32.
+        anchors (list|tuple): The anchor width and height, it will be parsed pair by pair.
+        class_num (int): The number of classes to predict.
+        conf_thresh (float): The confidence scores threshold of detection boxes. Boxes with confidence scores
+                    under threshold should be ignored.
+        downsample_ratio (int): The downsample ratio from network input to YoloBox operator input,
+                    so 32, 16, 8 should be set for the first, second, and thrid YoloBox operators.
+        clip_bbox (bool): Whether clip output bonding box in Input(ImgSize) boundary. Default true.
+        scale_x_y (float): Scale the center point of decoded bounding box. Default 1.0.
+        name (string): The default value is None.  Normally there is no need
+                       for user to set this property.  For more information,
+                       please refer to :ref:`api_guide_Name`
+
+    Returns:
+        boxes Tensor: A 3-D tensor with shape [N, M, 4], the coordinates of boxes,  N is the batch num,
+                    M is output box number, and the 3rd dimension stores [xmin, ymin, xmax, ymax] coordinates of boxes.
+        scores Tensor: A 3-D tensor with shape [N, M, :attr:`class_num`], the coordinates of boxes,  N is the batch num,
+                    M is output box number.
+                    
+    Raises:
+        TypeError: Attr anchors of yolo box must be list or tuple
+        TypeError: Attr class_num of yolo box must be an integer
+        TypeError: Attr conf_thresh of yolo box must be a float number
+
+    Examples:
+
+    .. code-block:: python
+
+        import paddle
+        
+        paddle.enable_static()
+        x = paddle.static.data(name='x', shape=[None, 255, 13, 13], dtype='float32')
+        img_size = paddle.static.data(name='img_size',shape=[None, 2],dtype='int64')
+        anchors = [10, 13, 16, 30, 33, 23]
+        boxes,scores = ops.yolo_box(x=x, img_size=img_size, class_num=80, anchors=anchors,
+                                        conf_thresh=0.01, downsample_ratio=32)
+    """
+    helper = LayerHelper('yolo_box', **locals())
+
+    if not isinstance(anchors, list) and not isinstance(anchors, tuple):
+        raise TypeError("Attr anchors of yolo_box must be list or tuple")
+    if not isinstance(class_num, int):
+        raise TypeError("Attr class_num of yolo_box must be an integer")
+    if not isinstance(conf_thresh, float):
+        raise TypeError("Attr ignore_thresh of yolo_box must be a float number")
+
+    if in_dygraph_mode():
+        attrs = ('anchors', anchors, 'class_num', class_num, 'conf_thresh',
+                 conf_thresh, 'downsample_ratio', downsample_ratio, 'clip_bbox',
+                 clip_bbox, 'scale_x_y', scale_x_y)
+        boxes, scores = core.ops.yolo_box(x, origin_shape, *attrs)
+        return boxes, scores
+
+    boxes = helper.create_variable_for_type_inference(dtype=x.dtype)
+    scores = helper.create_variable_for_type_inference(dtype=x.dtype)
+
+    attrs = {
+        "anchors": anchors,
+        "class_num": class_num,
+        "conf_thresh": conf_thresh,
+        "downsample_ratio": downsample_ratio,
+        "clip_bbox": clip_bbox,
+        "scale_x_y": scale_x_y,
+    }
+
+    helper.append_op(
+        type='yolo_box',
+        inputs={
+            "X": x,
+            "ImgSize": origin_shape,
+        },
+        outputs={
+            'Boxes': boxes,
+            'Scores': scores,
+        },
+        attrs=attrs)
+    return boxes, scores

ppdet/modeling/tests/test_ops.py

@@ -355,6 +355,8 @@ class TestIoUSimilarity(LayerTest):
         x_np = make_rois(h, w, [20], output_size)
         y_np = make_rois(h, w, [10], output_size)
         with self.static_graph():
+            program = Program()
+            with program_guard(program):
                 x = paddle.static.data(name='x', shape=[20, 4], dtype='float32')
                 y = paddle.static.data(name='y', shape=[10, 4], dtype='float32')
 
@@ -363,7 +365,9 @@ class TestIoUSimilarity(LayerTest):
                     feed={
                         'x': x_np,
                         'y': y_np,
-                }, fetch_list=[iou], with_lod=False)
+                    },
+                    fetch_list=[iou],
+                    with_lod=False)
 
         with self.dynamic_graph():
             x_dy = base.to_variable(x_np)
@@ -375,5 +379,85 @@ class TestIoUSimilarity(LayerTest):
         self.assertTrue(np.array_equal(iou_np, iou_dy_np))
 
 
+class TestYOLO_Box(LayerTest):
+    def test_yolo_box(self):
+
+        # x shape [N C H W], C=K * (5 + class_num), class_num=10, K=2
+        np_x = np.random.random([1, 30, 7, 7]).astype('float32')
+        np_origin_shape = np.array([[608, 608]], dtype='int32')
+        class_num = 10
+        conf_thresh = 0.01
+        downsample_ratio = 32
+        scale_x_y = 1.2
+
+        # static
+        with self.static_graph():
+            # x shape [N C H W], C=K * (5 + class_num), class_num=10, K=2
+            x = paddle.static.data(
+                name='x', shape=[1, 30, 7, 7], dtype='float32')
+            origin_shape = paddle.static.data(
+                name='origin_shape', shape=[1, 2], dtype='int32')
+
+            boxes, scores = ops.yolo_box(
+                x,
+                origin_shape, [10, 13, 30, 13],
+                class_num,
+                conf_thresh,
+                downsample_ratio,
+                scale_x_y=scale_x_y)
+
+            boxes_np, scores_np = self.get_static_graph_result(
+                feed={
+                    'x': np_x,
+                    'origin_shape': np_origin_shape,
+                    'anchors': [10, 13, 30, 13],
+                    'class_num': 10,
+                    'conf_thresh': 0.01,
+                    'downsample_ratio': 32,
+                    'scale_x_y': 1.0,
+                },
+                fetch_list=[boxes, scores],
+                with_lod=False)
+
+        # dygraph
+        with self.dynamic_graph():
+            x_dy = fluid.layers.assign(np_x)
+            origin_shape_dy = fluid.layers.assign(np_origin_shape)
+
+            boxes_dy, scores_dy = ops.yolo_box(
+                x_dy,
+                origin_shape_dy, [10, 13, 30, 13],
+                10,
+                0.01,
+                32,
+                scale_x_y=scale_x_y)
+
+            boxes_dy_np = boxes_dy.numpy()
+            scores_dy_np = scores_dy.numpy()
+
+            self.assertTrue(np.array_equal(boxes_np, boxes_dy_np))
+            self.assertTrue(np.array_equal(scores_np, scores_dy_np))
+
+    def test_yolo_box_error(self):
+        paddle.enable_static()
+        program = Program()
+        with program_guard(program):
+            # x shape [N C H W], C=K * (5 + class_num), class_num=10, K=2
+            x = paddle.static.data(
+                name='x', shape=[1, 30, 7, 7], dtype='float32')
+            origin_shape = paddle.static.data(
+                name='origin_shape', shape=[1, 2], dtype='int32')
+
+            self.assertRaises(
+                TypeError,
+                ops.yolo_box,
+                x,
+                origin_shape, [10, 13, 30, 13],
+                10.123,
+                0.01,
+                32,
+                scale_x_y=1.2)
+
+
 if __name__ == '__main__':
     unittest.main()