Python OpenCV —— bitwise

　　關於圖像的位操做，目的是爲了將一個logo覆蓋到另外一個圖片上。

# -*- coding: utf-8 -*-
"""
Created on Wed Sep 28 20:05:50 2016

@author: Administrator
"""

'''
位運算
Bitwise Operations
'''
import numpy as np
import cv2


def show(img_name,img_data):
	cv2.imshow(img_name,img_data)
	cv2.waitKey(0)
	cv2.destroyAllWindows()

# Load two images
img1 = cv2.imread('ml.png')
img2 = cv2.imread('opencv_logo.png')

# I want to put ligo on top-left corner,so I create a ROI
rows,cols,channels = img2.shape
roi = img1[0:rows,0:cols]
#show('roi',roi)

# Now create a mask of logo and create its inverse mask also
img2gray = cv2.cvtColor(img2,cv2.COLOR_BGR2GRAY)
#show('img2gray',img2gray)
# threshold 閥值函數
# grayscale image; threshold; maxval; function of style
# THRESH_BINARY 
ret, mask = cv2.threshold(img2gray,10,255,cv2.THRESH_BINARY)
#show('mask',mask)

mask_inv = cv2.bitwise_not(mask)
#show('mask_inv',mask_inv)
# Now black-out the area of logo in ROI
# sr1;sr2;dst;mask;
# dst 就是記錄結果的 mask 就是控制位
# 就是 2個數據都要先和mask按位和 而後再按位和 若是有mask這個參數的話
# 經過位的與運算，達到「掩蓋」的目的
img1_bg = cv2.bitwise_and(roi,roi,mask = mask_inv)
#show('img1_bg',img1_bg)

# Take only region of logo from logo image
img2_fg = cv2.bitwise_and(img2,img2,mask=mask)

#show('img2_fg',img2_fg)

# Put logo in ROI and modify the main image
dst = cv2.add(img1_bg,img2_fg)
show('dst',dst)

img1[0:rows,0:cols] = dst

show('res',img1)

　　輸出圖形（位置好像不太對。。。請忽略）：

　　這裏感謝交流羣裏廢帝和黃同窗幫助理解位運算。目前仍是不能深刻理解，再學習下吧。