| | Input: |
| | is a set of range numbers |
| | is a set of bounding boxes in the input image |
| | is a set of pixel maps’ strides |
| | Output: |
| | is the kth pixel map |
| (1) | for each level do |
| (2) | build a mesh grid Mi according to the stride at kth level |
| (3) | for each pixel xi, yi ∈ Mido |
| (4) | calculate the pixel center coordinate xc, yc |
| (5) | for each bounding box ∈ do |
| (6) | if xc, yc locates within then |
| (7) | compute distances d = (l, t, r, b) from the pixel center to the box’s boundary |
| (8) | if < max(l, t, r, b) < then |
| (9) | if the pixel xi, yi has not been marked positive then |
| (10) | mark the pixel xi, yi in a positive sample, assign regression target d, classification target t and centerness score c |
| (11) | else |
| (12) | compare 4 distances l, t, r, b with target d and replace with l, t, r, b if the corresponding value in d is larger. |
| (13) | end if |
| (14) | end if |
| (15) | end if |
| (16) | end for |
| (17) | end for |
| (18) | end for |
