Chapter 3 - OpenCV Basics - 1 - Basics

Install OpenCV

pip install opencv-python 
pip install opencv-contrib-python

I installed opencv-python on the command line, but every time I can't find cv2 in pycharm, I finally add dependencies to the project. The specific operations are as follows:

PyCharm->Settings->Project: Project Name->Python Interpreter -> Click + select version import (opencv-python:4.5.5.64 numpy:1.24.2)

read image

retval = cv2.imread("image file path"[,flags])

retval : read the return value of the picture, essentially an image array class

filename : the full filename of the read file

flags: read the logo, the details are as follows, the first line and the third line are equivalent, you can leave it blank, it is the original image

value	meaning	value
cv2.IMREAD_UNCHANGED	Keep the original format unchanged	-1
cv2.IMREAD_GRAYSCALE	Adjust the image to a single-channel grayscale image	0
cv2.IMREAD_COLOR	Adjust the image to a three-channel BGR image, this is the default value	1

display image

cv2.imshow(window_name,mat)

window_name: the displayed window name

mat is the read or processed image data

save Picture

vetval = cv2.imwrite( filename , img [,flag] )

vetval : save the result, success is True, failure is False

filename : the full path and name of the saved file, including the extension

img : the image to keep

flag: the format of the picture to be saved, can be filled, generally not filled

wait for key

retval = cv2.waitKey( [delay] )

retval: the return value of the button during the waiting time, specifically the ASC code of the button, if there is no button during the waiting time, return -1

delay: A parameter that can be filled in, indicating the waiting time for keyboard operations, in ms, when it is not filled or is 0 or a negative number, it means infinite waiting

After executing this method, the window displaying the picture has been displayed

destroy window

cv2.destroyAllWindows()

After judging the value of the button, judge whether to close and destroy all windows according to the selection (of course, you can not judge, and close the window directly after receiving the button)

Full code:

import cv2 as cv
# 读取图片 可不传图片格式参数,默认为原图 -1和1为原图 0为灰度图
lena = cv.imread("lena.jpg", -1)
# 显示图片 窗口名
cv.imshow("lena's face", lena)
# 保存图片
cv.imwrite("1_other_lena.jpg", lena)
# 窗口显示时间,单位为ms 0/-1为一直显示
cv.waitKey(0)
# 销毁窗口
cv.destroyAllWindows()

Chapter 3 - OpenCV Basics - 1 - Basics

Guess you like