图像基本操作

数据读取-图像

• cv2.IMREAD_COLOR：彩色图像
• cv2.IMREAD_GRAYSCALE：灰度图像

import cv2 #opencv读取的格式是BGR
import matplotlib.pyplot as plt
import numpy as np 
%matplotlib inline 

img=cv2.imread('cat.jpg')

#图像的显示,也可以创建多个窗口
cv2.imshow('image',img) 
# 等待时间，毫秒级，0表示任意键终止
cv2.waitKey(0) 
cv2.destroyAllWindows()

def cv_show(name,img):
    cv2.imshow(name,img) 
    cv2.waitKey(0) 
    cv2.destroyAllWindows()

 

数据读取-视频

• cv2.VideoCapture可以捕获摄像头，用数字来控制不同的设备，例如0,1。
• 如果是视频文件，直接指定好路径即可。

vc = cv2.VideoCapture('test.mp4')
# 检查是否打开正确
if vc.isOpened(): 
    oepn, frame = vc.read()
else:
    open = False

while open:
    ret, frame = vc.read()
    if frame is None:
        break
    if ret == True:
        gray = cv2.cvtColor(frame,  cv2.COLOR_BGR2GRAY)
        cv2.imshow('result', gray)
        if cv2.waitKey(100) & 0xFF == 27:
            break
vc.release()
cv2.destroyAllWindows()

 

截取部分图像数据

img=cv2.imread('cat.jpg')
cat=img[0:50,0:200] 
cv_show('cat',cat)

 

颜色通道提取

b,g,r=cv2.split(img)

img=cv2.merge((b,g,r))
img.shape

# 只保留R
cur_img = img.copy()
cur_img[:,:,0] = 0
cur_img[:,:,1] = 0
cv_show('R',cur_img)

 

 

边界填充

top_size,bottom_size,left_size,right_size = (50,50,50,50)

replicate = cv2.copyMakeBorder(img, top_size, bottom_size, left_size, right_size, borderType=cv2.BORDER_REPLICATE)
reflect = cv2.copyMakeBorder(img, top_size, bottom_size, left_size, right_size,cv2.BORDER_REFLECT)
reflect101 = cv2.copyMakeBorder(img, top_size, bottom_size, left_size, right_size, cv2.BORDER_REFLECT_101)
wrap = cv2.copyMakeBorder(img, top_size, bottom_size, left_size, right_size, cv2.BORDER_WRAP)
constant = cv2.copyMakeBorder(img, top_size, bottom_size, left_size, right_size,cv2.BORDER_CONSTANT, value=0)

import matplotlib.pyplot as plt
plt.subplot(231), plt.imshow(img, 'gray'), plt.title('ORIGINAL')
plt.subplot(232), plt.imshow(replicate, 'gray'), plt.title('REPLICATE')
plt.subplot(233), plt.imshow(reflect, 'gray'), plt.title('REFLECT')
plt.subplot(234), plt.imshow(reflect101, 'gray'), plt.title('REFLECT_101')
plt.subplot(235), plt.imshow(wrap, 'gray'), plt.title('WRAP')
plt.subplot(236), plt.imshow(constant, 'gray'), plt.title('CONSTANT')

plt.show()

 

数值计算

img_cat=cv2.imread('cat.jpg')
img_dog=cv2.imread('dog.jpg')
img_cat2= img_cat +10 
img_cat[:5,:,0]

 

图像融合

res = cv2.addWeighted(img_cat, 0.4, img_dog, 0.6, 0)
plt.imshow(res)

也可不设size,进行比例放缩