public class MultiBoxTarget
extends java.lang.Object
MultiBoxTarget is the class that computes the training targets for training a Single Shot
Detection (SSD) models.
The output from a Single Shot Detection (SSD) network would be class probabilities, box offset predictions, and the generated anchor boxes. The labels contain a class label and the bounding box for each object in the image. The generated anchor boxes are each a prior, and need loss computed for each of them. This requires that we assign a ground truth box to every one of them.
MultiBoxTarget takes an NDList containing (anchor boxes, labels, class
predictions) in that order. It computes the Intersection-over-Union (IoU) of each anchor box
against every ground-truth box. For every anchor box, it assigns a ground-truth box with maximum
IoU with respect to the anchor box if the IoU is greater than a given threshold. Once a
ground-truth box is assigned for each anchor box, it computes the offset of each anchor box with
respect to it's assigned ground-truth box.
MultiBoxTarget handles these tasks and returns an NDList containing (Bounding
box offsets, bounding box masks, class labels). Bounding box offsets and class labels are
computed as above. Bounding box masks is a mask array that contains either a 0 or 1, with the 0s
corresponding to the anchor boxes whose IoUs with the ground-truth boxes were less than the given
threshold.
| Modifier and Type | Class and Description |
|---|---|
static class |
MultiBoxTarget.Builder
The Builder to construct a
MultiBoxTarget object. |
| Constructor and Description |
|---|
MultiBoxTarget(MultiBoxTarget.Builder builder)
Creates a new instance of
MultiBoxTarget with the arguments from the given MultiBoxTarget.Builder. |
| Modifier and Type | Method and Description |
|---|---|
static MultiBoxTarget.Builder |
builder()
Creates a builder to build a
MultiBoxTarget. |
NDList |
target(NDList inputs)
Computes multi-box training targets.
|
public MultiBoxTarget(MultiBoxTarget.Builder builder)
MultiBoxTarget with the arguments from the given MultiBoxTarget.Builder.builder - the MultiBoxTarget.Builder with the necessary argumentspublic NDList target(NDList inputs)
inputs - a NDList of (anchors, labels, and class prediction) in that orderNDList containing (Bounding box offsets, bounding box masks, class labels)public static MultiBoxTarget.Builder builder()
MultiBoxTarget.