Why NMSboxes is not eleminating multiple bounding boxes?

First of all here is my code :

        image = cv2.imread(filePath)          height, width, channels = image.shape                    # USing blob function of opencv to preprocess image          blob = cv2.dnn.blobFromImage(image, 1 / 255.0, (416, 416),          swapRB=True, crop=False)          #Detecting objects          net.setInput(blob)          outs = net.forward(output_layers)                    # Showing informations on the screen          class_ids = []          confidences = []          boxes = []            for out in outs:              for detection in out:                  scores = detection[5:]                  class_id = np.argmax(scores)                  confidence = scores[class_id]                  if confidence > 0.7:                      # Object detected                      center_x = int(detection[0] * width)                      center_y = int(detection[1] * height)                      w = int(detection[2] * width)                      h = int(detection[3] * height)                        # Rectangle coordinates                      x = int(center_x - w / 2)                      y = int(center_y - h / 2)                        boxes.append([x, y, w, h])                      confidences.append(float(confidence))                      class_ids.append(class_id)                                        indexes = cv2.dnn.NMSBoxes(boxes, confidences,score_threshold=0.4,nms_threshold=0.8,top_k=1)                            font = cv2.FONT_HERSHEY_PLAIN          colors = np.random.uniform(0, 255, size=(len(classes), 3))          labels = ['bicycle','car','motorbike','bus','truck']          for i in range(len(boxes)):              if i in indexes:                  label = str(classes[class_ids[i]])                  if label in labels:                      x, y, w, h = boxes[i]                      color = colors[class_ids[i]]                      cv2.rectangle(image, (x, y), (x + w, y + h), color, 2)                      cv2.putText(image, label, (x, y + 30), font, 2, color, 3)          cv2.imshow(fileName,image)  

My Question is : Isn't cv2.dnn.NMSBoxes is suppose to eliminate multiple bounding boxes? then why I still get output like sample below :

What I expected is something like below :

Did I do something wrong with my code? Is there any better alternative? Thank you very much for your help.

https://stackoverflow.com/questions/66701910/why-nmsboxes-is-not-eleminating-multiple-bounding-boxes March 19, 2021 at 10:54AM