OPENCV摄像头读取视频

OpenCV 读取摄像头的代码示例

以下是几种使用 OpenCV 读取摄像头的常见方法：

1. 基础摄像头读取

import cv2

# 打开默认摄像头（通常是0）
cap = cv2.VideoCapture(0)

# 检查摄像头是否成功打开
if not cap.isOpened():
    print("无法打开摄像头")
    exit()

print("摄像头已打开，按 'q' 键退出")

while True:
    # 读取一帧
    ret, frame = cap.read()
    
    # 检查帧是否读取成功
    if not ret:
        print("无法读取帧")
        break
    
    # 显示帧
    cv2.imshow('摄像头', frame)
    
    # 按'q'键退出
    if cv2.waitKey(1) & 0xFF == ord('q'):
        break

# 释放资源
cap.release()
cv2.destroyAllWindows()

2. 设置摄像头参数

import cv2

cap = cv2.VideoCapture(0)

# 设置摄像头参数
cap.set(cv2.CAP_PROP_FRAME_WIDTH, 640)   # 宽度
cap.set(cv2.CAP_PROP_FRAME_HEIGHT, 480)  # 高度
cap.set(cv2.CAP_PROP_FPS, 30)            # 帧率

# 获取实际参数值
width = cap.get(cv2.CAP_PROP_FRAME_WIDTH)
height = cap.get(cv2.CAP_PROP_FRAME_HEIGHT)
fps = cap.get(cv2.CAP_PROP_FPS)

print(f"摄像头分辨率: {width}x{height}, 帧率: {fps}")

while True:
    ret, frame = cap.read()
    if not ret:
        break
    
    # 在画面上显示信息
    cv2.putText(frame, f"分辨率: {int(width)}x{int(height)}", (10, 30), 
                cv2.FONT_HERSHEY_SIMPLEX, 0.7, (0, 255, 0), 2)
    cv2.putText(frame, f"帧率: {fps}", (10, 60), 
                cv2.FONT_HERSHEY_SIMPLEX, 0.7, (0, 255, 0), 2)
    
    cv2.imshow('摄像头', frame)
    
    if cv2.waitKey(1) & 0xFF == ord('q'):
        break

cap.release()
cv2.destroyAllWindows()

3. 多摄像头读取

import cv2

# 尝试打开多个摄像头
caps = []
for i in range(3):  # 尝试打开0,1,2号摄像头
    cap = cv2.VideoCapture(i)
    if cap.isOpened():
        caps.append(cap)
        print(f"摄像头 {i} 已连接")
    else:
        print(f"摄像头 {i} 未连接")

if not caps:
    print("没有可用的摄像头")
    exit()

print(f"共找到 {len(caps)} 个摄像头")

while True:
    frames = []
    for i, cap in enumerate(caps):
        ret, frame = cap.read()
        if ret:
            # 在每帧上标记摄像头编号
            cv2.putText(frame, f"Camera {i}", (10, 30), 
                        cv2.FONT_HERSHEY_SIMPLEX, 1, (0, 255, 0), 2)
            frames.append(frame)
    
    if not frames:
        break
    
    # 合并显示多个摄像头画面
    if len(frames) == 1:
        combined = frames[0]
    elif len(frames) == 2:
        combined = cv2.hconcat(frames)
    else:
        # 对于3个或更多摄像头，可以调整布局
        top = cv2.hconcat(frames[:2])
        bottom = cv2.hconcat(frames[2:]) if len(frames) > 2 else frames[2]
        combined = cv2.vconcat([top, bottom]) if len(frames) > 2 else top
    
    cv2.imshow('多摄像头', combined)
    
    if cv2.waitKey(1) & 0xFF == ord('q'):
        break

# 释放所有摄像头
for cap in caps:
    cap.release()
cv2.destroyAllWindows()

4. 保存视频流

import cv2

cap = cv2.VideoCapture(0)

# 设置视频编码器和输出文件
fourcc = cv2.VideoWriter_fourcc(*'XVID')
out = cv2.VideoWriter('output.avi', fourcc, 20.0, (640, 480))

recording = False
print("按 'r' 开始/停止录制，按 'q' 退出")

while True:
    ret, frame = cap.read()
    if not ret:
        break
    
    # 如果正在录制，保存帧
    if recording:
        out.write(frame)
        cv2.putText(frame, "录制中...", (10, 30), 
                    cv2.FONT_HERSHEY_SIMPLEX, 1, (0, 0, 255), 2)
    
    cv2.imshow('摄像头', frame)
    
    key = cv2.waitKey(1) & 0xFF
    if key == ord('q'):
        break
    elif key == ord('r'):
        recording = not recording
        print("录制" if recording else "停止录制")

cap.release()
out.release()  # 释放视频写入器
cv2.destroyAllWindows()

5. 带简单图像处理的摄像头读取

import cv2
import numpy as np

cap = cv2.VideoCapture(0)

mode = 0  # 0: 原图, 1: 灰度, 2: 边缘检测, 3: 模糊
modes = ['原图', '灰度', '边缘检测', '模糊']

print("按 'm' 切换模式，按 'q' 退出")

while True:
    ret, frame = cap.read()
    if not ret:
        break
    
    # 根据模式处理图像
    if mode == 1:
        processed = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
        processed = cv2.cvtColor(processed, cv2.COLOR_GRAY2BGR)  # 转回BGR用于显示
    elif mode == 2:
        gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
        processed = cv2.Canny(gray, 100, 200)
        processed = cv2.cvtColor(processed, cv2.COLOR_GRAY2BGR)
    elif mode == 3:
        processed = cv2.GaussianBlur(frame, (15, 15), 0)
    else:
        processed = frame.copy()
    
    # 显示当前模式
    cv2.putText(processed, f"模式: {modes[mode]}", (10, 30), 
                cv2.FONT_HERSHEY_SIMPLEX, 0.7, (0, 255, 0), 2)
    
    cv2.imshow('摄像头', processed)
    
    key = cv2.waitKey(1) & 0xFF
    if key == ord('q'):
        break
    elif key == ord('m'):
        mode = (mode + 1) % len(modes)
        print(f"切换到模式: {modes[mode]}")

cap.release()
cv2.destroyAllWindows()

部分api解释：

ret, frame = cap.read()

• 第一个返回值 (ret)：布尔值（True/False），表示帧是否成功读取

• 第二个返回值 (frame)：如果读取成功，这是一个包含图像数据的 NumPy 数组

# 显示一帧图像
    cv2.imshow('frame', frame)

    # 如果按下'q'键，退出循环
    if cv2.waitKey(1) & 0xFF == ord('q'):
        break