一、opencv打开摄像头修改尺寸
1、首先导入相关库文件：
# import necessary packages
import cv2
# define the codec and create VideoWriter object
fourcc = cv2.VideoWriter_fourcc(*'XVID')
out = cv2.VideoWriter('output.avi',fourcc, 20.0, (640,480))2、接着打开摄像头：
# open the camera
cap = cv2.VideoCapture(0)
# set the width and height of the camera capture
cap.set(3, 640)
cap.set(4, 480)3、循环读取摄像头画面，完成尺寸的修改：
while(cap.isOpened()):
# read frames from the camera
ret, frame = cap.read()
if ret==True:
# resize the frame
frame = cv2.resize(frame, (800,600))
# write the resized frame
out.write(frame)
# display the resized frame
cv2.imshow('frame',frame)
# break if the 'q' key is pressed
if cv2.waitKey(1) & 0xFF == ord('q'):
break
else:
break
# release the video capture
cap.release()
# release the video writer
out.release()
# close all the frames
cv2.destroyAllWindows()二、opencv打开摄像头并识别图形形状
1、首先导入相关库文件：
# import the necessary packages
import imutils
import cv2
# define the lower and upper boundaries of the color of the object
colorLower = (24, 100, 100)
colorUpper = (44, 255, 255)2、接着打开摄像头：
# open the camera
cap = cv2.VideoCapture(0)3、循环读取摄像头画面，完成图形的识别：
while True:
# get a frame
ret, frame = cap.read()
# if we are unable to get a frame, this means we have reached the end of the video
if not ret:
break
# resize the frame, blur it, and convert it to the HSV color space
frame = imutils.resize(frame, width=600)
blurred = cv2.GaussianBlur(frame, (11, 11), 0)
hsv = cv2.cvtColor(blurred, cv2.COLOR_BGR2HSV)
# create a mask for the color of the object, then perform the bitwise and operation
mask = cv2.inRange(hsv, colorLower, colorUpper)
mask = cv2.erode(mask, None, iterations=2)
mask = cv2.dilate(mask, None, iterations=2)
# find contours in the mask and initialize the current (x, y) center of the object
cnts = cv2.findContours(mask.copy(), cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)
cnts = imutils.grab_contours(cnts)
center = None
# if we have found at least one contour, find the largest one and compute its minimum enclosing circle
if len(cnts) > 0:
c = max(cnts, key=cv2.contourArea)
((x, y), radius) = cv2.minEnclosingCircle(c)
M = cv2.moments(c)
center = (int(M["m10"] / M["m00"]), int(M["m01"] / M["m00"]))
# if the circle is big enough, draw it and label the current shape
if radius > 10:
cv2.circle(frame, (int(x), int(y)), int(radius), (0, 255, 255), 2)
cv2.putText(frame, "Circle", (int(x-radius),int(y-radius)), cv2.FONT_HERSHEY_SIMPLEX, 0.6, (0, 255, 255), 2)
# display the resulting frame
cv2.imshow("Frame", frame)
# if the 'q' key is pressed, stop the loop
if cv2.waitKey(1) & 0xFF == ord('q'):
break
# release the camera and close all windows
cap.release()
cv2.destroyAllWindows()三、opencv打开摄像头代码
使用opencv打开摄像头代码如下：
import cv2
cap = cv2.VideoCapture(0)
while(True):
# Capture frame-by-frame
ret, frame = cap.read()
# Display the resulting frame
cv2.imshow('frame',frame)
# if the 'q' key is pressed, stop the loop
if cv2.waitKey(1) & 0xFF == ord('q'):
break
# When everything done, release the capture
cap.release()
cv2.destroyAllWindows()四、opencv打开摄像头没画面
如果打开摄像头没有画面，可以检查一下以下两种情况：
1、检查摄像头是否连接好，是否以及设置为默认摄像头；
2、修改代码段中以下这句话：
cap = cv2.VideoCapture(0)将摄像头的索引修改为1或其他数字，即可打开其他连接上的摄像头。
五、opencv打开摄像头失败
如果打开摄像头失败，可以检查以下几个方面：
1、检查电脑是否有权限读取使用摄像头；
2、检查电脑是否有摄像头设备；
3、修改代码段中以下这句话，在其后添加superuser权限：
cap = cv2.VideoCapture(0)如下：
cap = cv2.VideoCapture(0, cv2.CAP_DSHOW)六、opencv打开摄像头python
在python中使用opencv打开摄像头的代码如下：
import cv2
cap = cv2.VideoCapture(0)
while(True):
# Capture frame-by-frame
ret, frame = cap.read()
# Display the resulting frame
cv2.imshow('frame',frame)
# if the 'q' key is pressed, stop the loop
if cv2.waitKey(1) & 0xFF == ord('q'):
break
# When everything done, release the capture
cap.release()
cv2.destroyAllWindows()七、opencv打开摄像头并捕捉图像
使用opencv打开摄像头并捕捉图像的代码如下：
import cv2
cap = cv2.VideoCapture(0)
while(True):
# Capture frame-by-frame
ret, frame = cap.read()
# Display the resulting frame
cv2.imshow('frame',frame)
# if the space bar is pressed, capture the current frame
if cv2.waitKey(1) == 32:
cv2.imwrite('image.jpg', frame)
print('Image captured')
# if the 'q' key is pressed, stop the loop
if cv2.waitKey(1) & 0xFF == ord('q'):
break
# When everything done, release the capture
cap.release()
cv2.destroyAllWindows()八、opencv打开摄像头并保存手势
使用opencv打开摄像头并保存手势的代码如下：
# import the necessary packages
import cv2
import os
# define the paths to the training images and the output directory
imagePaths = ["images/1.jpg", "images/2.jpg", "images/3.jpg",
"images/4.jpg", "images/5.jpg", "images/6.jpg",
"images/7.jpg", "images/8.jpg", "images/9.jpg"]
outputDir = "gestures"
# loop over the training images
for imagePath in imagePaths:
# load the image, convert it to grayscale, and blur it
image = cv2.imread(imagePath)
gray = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)
blurred = cv2.GaussianBlur(gray, (5, 5), 0)
# threshold the image, erode and dilate it
thresh = cv2.threshold(blurred, 60, 255, cv2.THRESH_BINARY)[1]
thresh = cv2.erode(thresh, None, iterations=2)
thresh = cv2.dilate(thresh, None, iterations=2)
# find contours in the thresholded image and sort the contours by area in descending order
cnts = cv2.findContours(thresh.copy(), cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)
cnts = cnts[0] if imutils.is_cv2() else cnts[1]
cnts = sorted(cnts, key=cv2.contourArea, reverse=True)[:1]
# initialize the hull list and loop over the contours
hull = []
for c in cnts:
# compute the convex hull of the contour
hull.append(cv2.convexHull(c))
# draw the contour and convex hull of the hand
drawing = np.zeros(image.shape[:2], dtype=np.uint8)
for i in range(len(cnts)):
cv2.drawContours(drawing, cnts, i, (255, 255, 255), -1)
cv2.drawContours(drawing, hull, i, (255, 255, 255), -1)
# save the image to disk
filename = os.path.splitext(os.path.basename(imagePath))[0] + ".png"
cv2.imwrite(os.path.join(outputDir, filename), drawing)九、opencv打开摄像头不显示
如果打开摄像头后没有显示，请检查以下几个方面：
1、检查opencv是否安装正确；
2、检查电脑是否有摄像头设备；
3、检查电脑是否设置了防火墙或者杀软是否对opencv进行了限制；
4、修改代码段中以下这句话，添加数据类型转换：
cv2.imshow('frame',frame)如下：
cv2.imshow('frame', np.uint8(frame))
