Plotting bounding box around detected object using template matching

Question

I made a yolo model, not relevant for this topic. It is working fine. I wanted to add the template matching for detecting arrows on detected object with yolo.

Here is my function for template matching which returns coordinates of an arrow. (NOTE: I tested it on a small (cropped) image because there might be many arrows on picture, but I am only interested on the arrows inside my firstly detected object with yolo algorithm.)

def detect_arrows(img_path, template_paths):
img = cv2.imread(img_path)
img = cv2.cvtColor(img, cv2.COLOR_BGR2RGB)

arrow_coords = []
for temp_path in template_paths:
    arrow_template = cv2.imread(temp_path)
    arrow_template = cv2.cvtColor(arrow_template, cv2.COLOR_BGR2RGB)

    height, width, channels = arrow_template.shape
    res = cv2.matchTemplate(img, arrow_template, cv2.TM_CCOEFF)
    min_val, max_val, min_loc, max_loc = cv2.minMaxLoc(res)
    top_left = max_loc
    bottom_right = (top_left[0] + width, top_left[1] + height)
    arrow_coords.append((top_left, bottom_right))

return arrow_coords

When I test that function on a single image, it works perfectly. But now, when I want to add it to my yolo algorithm, it doesnt draw arrow bounding box on the correct spot.

This is my current code:

           for *xyxy, conf, cls in reversed(det):
                object_coordinates = [int(xyxy[0]),int(xyxy[1]),int(xyxy[2]),int(xyxy[3])]
                cropobj = im0[int(xyxy[1]):int(xyxy[3]),int(xyxy[0]):int(xyxy[2])] 

                gray_cropobj = cv2.cvtColor(cropobj, cv2.COLOR_BGR2GRAY)
                gray_cropobj = cv2.bitwise_not(gray_cropobj)

                crop_file_path = os.path.join("crop",str(crop_count)+".jpg")
                cv2.imwrite(crop_file_path, gray_cropobj)
                crop_count = crop_count + 1

                up_path = r'C:\Users\qwe\Desktop\up.jpg'
                up_right_path = r'C:\Users\qwe\Desktop\up_right.jpg'

                img_path = crop_file_path
                
                arrow_coords = detect_arrows(crop_file_path, template_paths=[up_path, up_right_path])

                if save_txt:  # Write to file
                    xywh = (xyxy2xywh(torch.tensor(xyxy).view(1, 4)) / gn).view(-1).tolist()  # normalized xywh
                    line = (cls, *xywh, conf) if opt.save_conf else (cls, *xywh)  # label format
                    with open(txt_path + '.txt', 'a') as f:
                        f.write(('%g ' * len(line)).rstrip() % line + '\n')

                if save_img or view_img:  # Add bbox to image
                    label = f'{names[int(cls)]} {conf:.2f}'
                    plot_one_box(xyxy, im0, label=label, color=colors[int(cls)], line_thickness=1)
                    for arrow_coord in arrow_coords:
                        top_left, bottom_right = arrow_coord
                        arrow_top_left = (int(xyxy[0]) + top_left[0], int(xyxy[1]) + top_left[1])
                        arrow_bottom_right = (int(xyxy[0]) + bottom_right[0], int(xyxy[1]) + bottom_right[1])
                        cv2.rectangle(im0, arrow_top_left, arrow_bottom_right, (0, 255,255), 1, cv2.LINE_AA)

it draws inside firstly detected object, but not around the arrow, it draws on the wrong spot. I tried with scaling between the cropped picture, adding offset, printing the coordinates to debug it, but nothing seems to be working.

So, I want to detect arrows on the cropped picture and plot it on the first original image (inside of firstly detected object, its coordinates).

Plotting bounding box around detected object using template matching

0 Answers0