opencv-python实例系列一-摄像头图片视频操作

1、加载一张图片，并且在窗口中显示

import cv2

img = cv2.imread('北京.jpg') # 导入图片

# cv2.namedWindow('Image')
# cv2.imshow('Image', img)
cv2.imshow('my image', img)
cv2.waitKey(0) # 不加这一条会无响应，这也太奇怪了，直接给我卡死了
cv2.destroyAllWindows()

打印img的类型，是numpy的数组

2、BGR转化为灰度图片

import cv2

img = cv2.imread('北京.jpg')
img = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
cv2.imwrite('北京.png', img)
cv2.imshow('Image', img)
cv2.waitKey()
cv2.destroyWindow("Image")

在pycharm中查看相关的方法，有各种图片转化的模式。

3、调用摄像头并保存为视频

调用VideoCapture类
可以设置帧率
可以设置图片的大小
设置拍摄的时长：通过计算帧来实现
cameraCapture.read()返回两个参数，一是否成功，二图片frame
打印frame类型

import cv2

cameraCapture = cv2.VideoCapture(0)
fps = 30
size = (int(cameraCapture.get(cv2.CAP_PROP_FRAME_WIDTH)),
        int(cameraCapture.get(cv2.CAP_PROP_FRAME_HEIGHT)))
print('width={0}, height={1}'.format(
    int(cameraCapture.get(cv2.CAP_PROP_FRAME_WIDTH)),
    int(cameraCapture.get(cv2.CAP_PROP_FRAME_HEIGHT))
))

videoWriter = cv2.VideoWriter(
    'MyOutputVid.avi', cv2.VideoWriter_fourcc('I', '4', '2', '0'),\
    fps, size
)

success, frame = cameraCapture.read()
numFramesRemaining = 10 * fps - 1
while success and numFramesRemaining > 0:
    videoWriter.write(frame)
    success, frame = cameraCapture.read()
    numFramesRemaining -= 1
cameraCapture.release()

4、调用摄像头并在窗口中显示

调用摄像头，在窗口中显示。捕获键盘和鼠标活动，例如鼠标单击退出窗口，安任意建退出。

import cv2

clicked = False
def onMouse(event, x, y, flags, param): # 鼠标触发的事件
    global clicked
    if event == cv2.EVENT_LBUTTONUP: # 左键松开
        clicked = True
    return

cameraCapture = cv2.VideoCapture(0)
cv2.namedWindow('Video')
cv2.setMouseCallback('Video', onMouse)

print("正在读取摄像头，按任意建或者左键点击退出")

success, frame = cameraCapture.read()
while success and cv2.waitKey(1) == -1 and not clicked:
    cv2.imshow('Video', frame)
    # cv2.imshow('Video2', frame) # 多个窗口
    success, frame = cameraCapture.read()

cv2.destroyWindow('Video')
cameraCapture.release()

事件对应的表

书上是这么说的