refactor api

api/src/common/boxes.py

@@ -0,0 +1,64 @@
+"""Bounding box helpers. Boxes are [xmin, ymin, xmax, ymax] unless noted.
+
+Used by training and by the production server, so keep this free of
+training-only dependencies."""
+
+
+def iou(boxA, boxB):
+    xA = max(boxA[0], boxB[0])
+    yA = max(boxA[1], boxB[1])
+    xB = min(boxA[2], boxB[2])
+    yB = min(boxA[3], boxB[3])
+
+    inter_area = max(0, xB - xA) * max(0, yB - yA)
+
+    boxA_area = (boxA[2] - boxA[0]) * (boxA[3] - boxA[1])
+    boxB_area = (boxB[2] - boxB[0]) * (boxB[3] - boxB[1])
+
+    union = boxA_area + boxB_area - inter_area
+
+    return inter_area / union if union > 0 else 0
+
+
+def nms(bboxes, iou_threshold=0.1):
+    """bboxes: [confidence, xmin, ymin, xmax, ymax]. Returns boxes without
+    the confidence, highest confidence first."""
+    bboxes = sorted(bboxes, key=lambda x: x[0], reverse=True)
+
+    keep = []
+    while bboxes:
+        best = bboxes.pop(0)
+        keep.append(best[1:5])
+        bboxes = [box for box in bboxes if iou(best[1:5], box[1:5]) < iou_threshold]
+
+    return keep
+
+
+def xy_center_to_edges(xcenter, ycenter, width, height):
+    width = max(width, 1)
+    height = max(height, 1)
+
+    x = xcenter - (width / 2)
+    y = ycenter - (height / 2)
+
+    return [x, y, x + width, y + height]
+
+
+def cell_to_image_coords(x, y, img_w, img_h, S, cell_i, cell_j):
+    """Grid-cell-relative position -> image position."""
+    return x + (img_w / S) * cell_i, y + (img_h / S) * cell_j
+
+
+def image_to_cell_coords(x, y, img_w, img_h, S, cell_i, cell_j):
+    """Image position -> grid-cell-relative position."""
+    return x - (img_w / S) * cell_i, y - (img_h / S) * cell_j
+
+
+def is_center_in_grid_cell(x, y, img_w, img_h, S, cell_i, cell_j):
+    gt_cell_i = min(int(x / (img_w / S)), S - 1)
+    gt_cell_j = min(int(y / (img_h / S)), S - 1)
+    return (gt_cell_i == cell_i) and (gt_cell_j == cell_j)
+
+
+def scale_box(box, scale_w, scale_h):
+    return [int(box[0] * scale_w), int(box[1] * scale_h), int(box[2] * scale_w), int(box[3] * scale_h)]