Proposal#
Versioned name: Proposal-1
Category: Object detection
Short description: Proposal operation filters bounding boxes and outputs only those with the highest prediction confidence.
Detailed description
Proposal has three inputs: a tensor with probabilities whether particular bounding box corresponds to background and foreground, a tensor with bbox_deltas for each of the bounding boxes, a tensor with input image size in the [image_height
, image_width
, scale_height_and_width
] or [image_height
, image_width
, scale_height
, scale_width
] format. The produced tensor has two dimensions [batch_size * post_nms_topn, 5]
, and for each output box contains batch index and box coordinates.
Proposal layer does the following with the input tensor:
Generates initial anchor boxes. Left top corner of all boxes is at (0, 0). Width and height of boxes are calculated from base_size with scale and ratio attributes.
For each point in the first input tensor:
pins anchor boxes to the image according to the second input tensor that contains four deltas for each box: for x and y of center, for width and for height
finds out score in the first input tensor
Filters out boxes with size less than min_size
Sorts all proposals (box, score) by score from highest to lowest
Takes top pre_nms_topn proposals
Calculates intersections for boxes and filter out all boxes with \(intersection/union > nms\_thresh\)
Takes top post_nms_topn proposals
Returns top proposals, if there is not enough proposals to fill the whole output tensor, the valid proposals will be terminated with a single -1.
Attributes:
base_size
Description: base_size is the size of the anchor to which scale and ratio attributes are applied.
Range of values: a positive integer number
Type:
int
Required: yes
pre_nms_topn
Description: pre_nms_topn is the number of bounding boxes before the NMS operation. For example, pre_nms_topn equal to 15 means to take top 15 boxes with the highest scores.
Range of values: a positive integer number
Type:
int
Required: yes
post_nms_topn
Description: post_nms_topn is the number of bounding boxes after the NMS operation. For example, post_nms_topn equal to 15 means to take after NMS top 15 boxes with the highest scores.
Range of values: a positive integer number
Type:
int
Required: yes
nms_thresh
Description: nms_thresh is the minimum value of the proposal to be taken into consideration. For example, nms_thresh equal to 0.5 means that all boxes with prediction probability less than 0.5 are filtered out.
Range of values: a positive floating-point number
Type:
float
Required: yes
feat_stride
Description: feat_stride is the step size to slide over boxes (in pixels). For example, feat_stride equal to 16 means that all boxes are analyzed with the slide 16.
Range of values: a positive integer
Type:
int
Required: yes
min_size
Description: min_size is the minimum size of box to be taken into consideration. For example, min_size equal 35 means that all boxes with box size less than 35 are filtered out.
Range of values: a positive integer number
Type:
int
Required: yes
ratio
Description: ratio is the ratios for anchor generation.
Range of values: a list of floating-point numbers
Type:
float[]
Required: yes
scale
Description: scale is the scales for anchor generation.
Range of values: a list of floating-point numbers
Type:
float[]
Required: yes
clip_before_nms
Description: clip_before_nms flag that specifies whether to perform clip bounding boxes before non-maximum suppression or not.
Range of values: true or false
Type:
boolean
Default value: true
Required: no
clip_after_nms
Description: clip_after_nms is a flag that specifies whether to perform clip bounding boxes after non-maximum suppression or not.
Range of values: true or false
Type:
boolean
Default value: false
Required: no
normalize
Description: normalize is a flag that specifies whether to perform normalization of output boxes to [0,1] interval or not.
Range of values: true or false
Type:
boolean
Default value: false
Required: no
box_size_scale
Description: box_size_scale specifies the scale factor applied to bbox_deltas of box sizes before decoding.
Range of values: a positive floating-point number
Type:
float
Default value: 1.0
Required: no
box_coordinate_scale
Description: box_coordinate_scale specifies the scale factor applied to bbox_deltas of box coordinates before decoding.
Range of values: a positive floating-point number
Type:
float
Default value: 1.0
Required: no
framework
Description: framework specifies how the box coordinates are calculated.
Range of values:
“” (empty string) - calculate box coordinates like in Caffe
tensorflow - calculate box coordinates like in the TensorFlow* Object Detection API models
Type: string
Default value: “” (empty string)
Required: no
Inputs:
1: 4D tensor of type T and shape
[batch_size, 2*K, H, W]
with class prediction scores. Required.2: 4D tensor of type T and shape
[batch_size, 4*K, H, W]
with deltas for each bounding box. Required.3: 1D tensor of type T with 3 or 4 elements:
[image_height, image_width, scale_height_and_width]
or[image_height, image_width, scale_height, scale_width]
. Required.
Outputs:
1: Tensor of type T and shape
[batch_size * post_nms_topn, 5]
.
Types
T: floating-point type.
Example
<layer ... type="Proposal" ... >
<data base_size="16" feat_stride="16" min_size="16" nms_thresh="0.6" post_nms_topn="200" pre_nms_topn="6000"
ratio="2.67" scale="4.0,6.0,9.0,16.0,24.0,32.0"/>
<input> ... </input>
<output> ... </output>
</layer>