obb_crop.py

import ultralytics
from ultralytics import YOLO
import matplotlib.pyplot as plt
import cv2 
import numpy as np 

print(ultralytics.__version__)

def crop_obb(image, obb):
    """ Crop the Oriented Bounding Box (OBB) """
    x_c, y_c, w, h, angle = obb
    center = (x_c, y_c)
    size = (w, h)
    angle_deg = np.degrees(angle)

    # Rotated rectangle
    rot_rect = ((x_c, y_c), (w, h), angle_deg)

    # Get the rotation matrix
    box = cv2.boxPoints(rot_rect)
    box = np.int0(box)

    # Crop the bounding box region
    width = int(w)
    height = int(h)
    src_pts = box.astype("float32")
    dst_pts = np.array([[0, height-1],
                        [0, 0],
                        [width-1, 0],
                        [width-1, height-1]], dtype="float32")
    
    M = cv2.getPerspectiveTransform(src_pts, dst_pts)
    cropped_img = cv2.warpPerspective(image, M, (width, height))
    
    return cropped_img


model = YOLO("yolo11n-obb.pt")
results = model("https://ultralytics.com/images/boats.jpg")  # predict on an image
results[0].show()  # display the image

cropped_img = crop_obb(results[0].orig_img, results[0].obb.xywhr[0].cpu().numpy())
plt.imshow(cropped_img)