import cv2
import os

def select_and_output_roi(img_path, save=True, save_dir="roi_output"):
    img = cv2.imread(img_path)
    if img is None:
        raise RuntimeError("无法读取图片")

    # OpenCV 自带 ROI 选择工具
    roi = cv2.selectROI(
        windowName="Select ROI (ENTER or C to confirm, ESC to quit)",
        img=img,
        showCrosshair=True,
        fromCenter=False
    )

    cv2.destroyAllWindows()

    x, y, w, h = roi
    print(f"[INFO] ROI = (x={x}, y={y}, w={w}, h={h})")

    roi_img = img[y:y+h, x:x+w]

    if save:
        os.makedirs(save_dir, exist_ok=True)
        save_path = os.path.join(save_dir, "roi.png")
        cv2.imwrite(save_path, roi_img)
        print(f"[INFO] ROI 图像已保存: {save_path}")

    return roi, roi_img


# ----------------------------
# main 测试
# ----------------------------
if __name__ == "__main__":
    IMAGE_PATH = "test2.png"   # 换成你的图片

    roi, roi_img = select_and_output_roi(
        IMAGE_PATH,
        save=True
    )

    cv2.imshow("ROI Result", roi_img)
    cv2.waitKey(0)
    cv2.destroyAllWindows()