要实现通过相机确定物品坐标位置，通常需要相机标定、物体检测和坐标转换几个步骤。下面我将提供一个完整的解决方案，包括相机标定、物体检测和3D坐标估计。
1. 系统架构
-
相机标定 - 获取相机内参和畸变系数
-
物体检测 - 使用OpenCV或深度学习模型检测物品
-
坐标转换 - 将2D图像坐标转换为3D世界坐标
-
ROS2集成 - 将上述功能集成到ROS2节点中
2. 实现步骤
2.1 创建功能包
bash
ros2 pkg create object_localization --build-type ament_python --dependencies rclpy sensor_msgs cv_bridge opencv-python geometry_msgs
2.2 相机标定节点
首先实现相机标定节点，用于获取相机内参和畸变系数。
在object_localization/object_localization目录下创建camera_calibration.py:
python
#!/usr/bin/env python3
import rclpy
from rclpy.node import Node
import cv2
import numpy as np
import os
from sensor_msgs.msg import Image
from cv_bridge import CvBridge
class CameraCalibrationNode(Node):
def __init__(self):
super().__init__('camera_calibration_node')
# 参数
self.declare_parameter('chessboard_width', 9)
self.declare_parameter('chessboard_height', 6)
self.declare_parameter('square_size', 0.025) # 25mm
self.declare_parameter('calibration_images_dir', 'calibration_images')
self.declare_parameter('save_file', 'camera_calibration.yaml')
self.chessboard_width = self.get_parameter('chessboard_width').value
self.chessboard_height = self.get_parameter('chessboard_height').value
self.square_size = self.get_parameter('square_size').value
self.calibration_images_dir = self.get_parameter('calibration_images_dir').value
self.save_file = self.get_parameter('save_file').value
# 创建目录
os.makedirs(self.calibration_images_dir, exist_ok=True)
# 初始化
self.bridge = CvBridge()
self.subscription = self.create_subscription(
Image,
'image_raw',
self.image_callback,
10)
self.criteria = (cv2.TERM_CRITERIA_EPS + cv2.TERM_CRITERIA_MAX_ITER, 30, 0.001)
self.objp = np.zeros((self.chessboard_height*self.chessboard_width, 3), np.float32)
self.objp[:,:2] = np.mgrid[0:self.chessboard_width, 0:self.chessboard_height].T.reshape(-1,2) * self.square_size
self.objpoints = [] # 3D点
self.imgpoints = [] # 2D点
self.get_logger().info("Camera calibration node ready. Point camera at chessboard...")
def image_callback(self, msg):
try:
frame = self.bridge.imgmsg_to_cv2(msg, "bgr8")
gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
# 查找棋盘格角点
ret, corners = cv2.findChessboardCorners(gray, (self.chessboard_width, self.chessboard_height), None)
if ret:
corners2 = cv2.cornerSubPix(gray, corners, (11,11), (-1,-1), self.criteria)
# 绘制并显示角点
cv2.drawChessboardCorners(frame, (self.chessboard_width, self.chessboard_height), corners2, ret)
cv2.imshow('Calibration', frame)
key = cv2.waitKey(1)
if key == ord('s'):
# 保存当前帧用于标定
img_path = os.path.join(self.calibration_images_dir, f'calib_{len(self.objpoints)}.png')
cv2.imwrite(img_path, frame)
self.objpoints.append(self.objp)
self.imgpoints.append(corners2)
self.get_logger().info(f"Saved calibration image {img_path}")
elif key == ord('c'):
# 执行标定
self.calibrate_camera()
except Exception as e:
self.get_logger().error(f"Error processing image: {e}")
def calibrate_camera(self):
if len(self.objpoints) < 5:
self.get_logger().warning("Need at least 5 images for calibration")
return
try:
ret, mtx, dist, rvecs, tvecs = cv2.calibrateCamera(
self.objpoints, self.imgpoints,
(self.objpoints[0].shape[1], self.objpoints[0].shape[0]),
None, None)
# 保存标定结果
calibration_data = {
'camera_matrix': mtx.tolist(),
'distortion_coefficients': dist.tolist()
}
import yaml
with open(self.save_file, 'w') as f:
yaml.dump(calibration_data, f)
self.get_logger().info(f"Calibration completed. Results saved to {self.save_file}")
self.get_logger().info(f"Camera matrix:\n{mtx}")
self.get_logger().info(f"Distortion coefficients:\n{dist}")
# 计算重投影误差
mean_error = 0
for i in range(len(self.objpoints)):
imgpoints2, _ = cv2.projectPoints(self.objpoints[i], rvecs[i], tvecs[i], mtx, dist)
error = cv2.norm(self.imgpoints[i], imgpoints2, cv2.NORM_L2)/len(imgpoints2)
mean_error += error
self.get_logger().info(f"Total reprojection error: {mean_error/len(self.objpoints)}")
except Exception as e:
self.get_logger().error(f"Calibration failed: {e}")
def main(args=None):
rclpy.init(args=args)
node = CameraCalibrationNode()
rclpy.spin(node)
node.destroy_node()
rclpy.shutdown()
if __name__ == '__main__':
main()
2.3 物体定位节点
创建object_localization_node.py用于检测物体并计算其3D坐标：
python
#!/usr/bin/env python3
import rclpy
from rclpy.node import Node
from sensor_msgs.msg import Image, CameraInfo
from geometry_msgs.msg import PointStamped
from cv_bridge import CvBridge
import cv2
import numpy as np
import yaml
class ObjectLocalizationNode(Node):
def __init__(self):
super().__init__('object_localization_node')
# 参数
self.declare_parameter('calibration_file', 'camera_calibration.yaml')
self.declare_parameter('object_height', 0.0) # 物体高度(相对于相机)
self.declare_parameter('target_color_low', [0, 100, 100])
self.declare_parameter('target_color_high', [10, 255, 255])
self.calibration_file = self.get_parameter('calibration_file').value
self.object_height = self.get_parameter('object_height').value
self.target_color_low = np.array(self.get_parameter('target_color_low').value, np.uint8)
self.target_color_high = np.array(self.get_parameter('target_color_high').value, np.uint8)
# 加载相机标定数据
self.camera_matrix = None
self.dist_coeffs = None
self.load_calibration_data()
# 初始化
self.bridge = CvBridge()
self.image_sub = self.create_subscription(
Image,
'image_raw',
self.image_callback,
10)
self.camera_info_sub = self.create_subscription(
CameraInfo,
'camera_info',
self.camera_info_callback,
10)
self.position_pub = self.create_publisher(
PointStamped,
'object_position',
10)
self.get_logger().info("Object localization node ready")
def load_calibration_data(self):
try:
with open(self.calibration_file, 'r') as f:
calibration_data = yaml.safe_load(f)
self.camera_matrix = np.array(calibration_data['camera_matrix'])
self.dist_coeffs = np.array(calibration_data['distortion_coefficients'])
self.get_logger().info("Loaded camera calibration data")
except Exception as e:
self.get_logger().error(f"Failed to load calibration data: {e}")
def camera_info_callback(self, msg):
if self.camera_matrix is None:
self.camera_matrix = np.array(msg.k).reshape(3, 3)
self.dist_coeffs = np.array(msg.d)
self.get_logger().info("Received camera info")
def image_callback(self, msg):
if self.camera_matrix is None:
self.get_logger().warn("Camera calibration data not available yet")
return
try:
frame = self.bridge.imgmsg_to_cv2(msg, "bgr8")
# 1. 预处理图像
hsv = cv2.cvtColor(frame, cv2.COLOR_BGR2HSV)
mask = cv2.inRange(hsv, self.target_color_low, self.target_color_high)
# 2. 形态学操作
kernel = np.ones((5,5), np.uint8)
mask = cv2.morphologyEx(mask, cv2.MORPH_OPEN, kernel)
mask = cv2.morphologyEx(mask, cv2.MORPH_CLOSE, kernel)
# 3. 查找轮廓
contours, _ = cv2.findContours(mask, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)
if len(contours) > 0:
# 找到最大轮廓
largest_contour = max(contours, key=cv2.contourArea)
# 计算轮廓的矩
M = cv2.moments(largest_contour)
if M['m00'] > 0:
# 计算中心点
cx = int(M['m10']/M['m00'])
cy = int(M['m01']/M['m00'])
# 4. 计算3D位置
object_point = self.calculate_3d_position(cx, cy)
if object_point is not None:
# 发布位置
position_msg = PointStamped()
position_msg.header.stamp = self.get_clock().now().to_msg()
position_msg.header.frame_id = "camera"
position_msg.point.x = object_point[0]
position_msg.point.y = object_point[1]
position_msg.point.z = object_point[2]
self.position_pub.publish(position_msg)
# 可视化
cv2.circle(frame, (cx, cy), 5, (0, 0, 255), -1)
cv2.putText(frame, f"({object_point[0]:.2f}, {object_point[1]:.2f}, {object_point[2]:.2f})",
(cx+10, cy), cv2.FONT_HERSHEY_SIMPLEX, 0.5, (0, 255, 0), 1)
# 显示结果
cv2.imshow('Object Detection', frame)
cv2.waitKey(1)
except Exception as e:
self.get_logger().error(f"Error processing image: {e}")
def calculate_3d_position(self, u, v):
"""
根据2D图像坐标计算3D世界坐标
假设物体位于地面平面(Z=object_height)
"""
try:
# 归一化图像坐标
uv_point = np.array([[u, v]], dtype=np.float32)
uv_point = np.array([uv_point])
# 去畸变
normalized_point = cv2.undistortPoints(uv_point, self.camera_matrix, self.dist_coeffs)
normalized_point = normalized_point[0][0]
# 计算3D坐标
fx = self.camera_matrix[0, 0]
fy = self.camera_matrix[1, 1]
cx = self.camera_matrix[0, 2]
cy = self.camera_matrix[1, 2]
# 相机坐标系中的坐标
x = (normalized_point[0] - cx) / fx
y = (normalized_point[1] - cy) / fy
# 假设物体高度已知
Z = self.object_height
X = x * Z
Y = y * Z
return (X, Y, Z)
except Exception as e:
self.get_logger().error(f"Error calculating 3D position: {e}")
return None
def main(args=None):
rclpy.init(args=args)
node = ObjectLocalizationNode()
rclpy.spin(node)
node.destroy_node()
rclpy.shutdown()
if __name__ == '__main__':
main()
2.4 启动文件
创建launch/object_localization.launch.py:
python
from launch import LaunchDescription
from launch_ros.actions import Node
def generate_launch_description():
return LaunchDescription([
Node(
package='object_localization',
executable='object_localization_node',
name='object_localization_node',
parameters=[
{'calibration_file': 'camera_calibration.yaml'},
{'object_height': 0.5}, # 假设物体高度为0.5米
{'target_color_low': [0, 100, 100]},
{'target_color_high': [10, 255, 255]}
]
)
])
3. 使用说明
3.1 相机标定
-
打印一个棋盘格图案(例如9x6)
-
运行标定节点:
bash
-
ros2 run object_localization camera_calibration_node
-
将棋盘格以不同角度展示给相机，按's'键保存图像
-
收集足够多(建议15-20张)图像后，按'c'键进行标定
-
标定结果将保存到
camera_calibration.yaml
3.2 物体定位
-
运行物体定位节点:
bash
-
ros2 launch object_localization object_localization.launch.py
-
确保目标物体颜色在
target_color_low和target_color_high范围内 -
节点将发布检测到的物体位置到
/object_position话题
3.3 可视化
可以使用RViz查看物体位置:
bash
ros2 run rviz2 rviz2
添加PointStamped显示，设置话题为/object_position
4. 高级改进建议
-
使用深度学习模型 - 替换简单的颜色检测，使用YOLO等模型进行更准确的物体检测
-
多相机融合 - 使用多个相机进行三角测量，提高定位精度
-
深度相机支持 - 集成RealSense或Kinect等深度相机，直接获取深度信息
-
坐标变换 - 使用TF2将物体坐标转换到世界坐标系
-
AR标记检测 - 使用AprilTag或Aruco标记进行更精确的定位
这个实现提供了基于单目相机和已知高度的物体定位方法。对于更复杂的场景，可能需要结合深度信息或其他传感器数据。
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