#!/usr/bin/env python
# coding: utf-8

# # Linux terminal essential

# ```
# cd ..                                                       
# cd # back to home dir                                       
# cd ~/p2 # ~ means home dir as well                             
# 
# ls # dir
# ```
# 
# \# install vim: sudo is to notify running as administrater,                         
# \# apt-get install to install package,                     
# \# vim is a common editor (extension of vi)                 
# ```
# sudo apt-get install vim 
# sudo apt-cache search vim # search packages relating to vi
# ```
# 
# ```
# gedit tmp.py # open to edit a file                        
# ctrl-z # break the current job                                   
# bg # send job to background                                              
# fg # send job back to foreground                                      
# ctrl-c # kill foreground job                                           
# ps aux | grep gedit # list all jobs and then search for "gedit" jobs              
# kill -9 12345 # kill job with job number 12345                                        
# ```
# 
# \# extract the audio channel of dummy.mp4                                     
# \# audio format suppose to be aac though                                     
# \# change extension (.ac3/.flac) accordingly                                       
# ```
# ffmpeg -i dummy.mp4 -acodec copy -vn audio.aac                   
# ```
# 
# #extract audio channels from all mp4 files in current folder    
# ```
# ls -1 \*.mp4|sed 's/\(.*\)\.mp4/ffmpeg -i "&" -acodec copy -vn "\1.aac"/'|sh
# ```
# 

# # Setup virtualenv (tested on Ubuntu 18.04) 

# ```
# sudo apt-get install python-virtualenv
# virtualenv ~/p2 # create a virtualenv with python2
# virtualenv --python=/usr/bin/python3 ~/p3 # create a virtualenv with python3
# source ~/p2/bin/activate
# ```

# # Install opencv

# ```
# source ~/p2/bin/activate # make sure you have create virtualenv already, see above.
# pip install numpy # install numpy (matlab like library for scientific computing). 
#                   # Note that we don't include sudo here as we are installing to the virtualenv 
# pip install opencv-python
# pip install opencv-contrib-python
# pip install opencv-python==3.4.5.20 # install a particular version
# pip install -U opencv-python # upgrade to latest
# 
# pip search opencv # search packages relating to opencv
# ```

# ## Load image with opencv

# In[74]:


import cv2
import matplotlib.pyplot as plt
import numpy as np
from skimage import io
import os.path

filename='Lena.png'
if os.path.isfile(filename):
    im=cv2.imread('Lena.png') 
else: 
    im=io.imread('http://optipng.sourceforge.net/pngtech/img/lena.png') 
# note that io.imread and cv2.imread handle images differently, io.imread compatible with plt.imshow directly


# ## Display with matplotlib

# In[75]:


get_ipython().run_line_magic('matplotlib', 'inline')
plt.imshow(im)


# ## resize image

# In[76]:


ims=cv2.resize(im,(128,128))


# ## rearrange color component and display image

# In[77]:


im2=np.zeros_like(ims)
im2[:,:,0]=ims[:,:,2]
im2[:,:,1]=ims[:,:,1]
im2[:,:,2]=ims[:,:,0]

plt.imshow(im2)


# ## set r as the first component, edit r, and display the original image

# In[78]:


r=im2[:,:,0] 

r[:,50:100]=0

plt.imshow(im2) # note that the original image was modified as well. You may find this surprising 
                # if you are used to the MATLAB world
                # this article may help 
                # https://jeffknupp.com/blog/2012/11/13/is-python-callbyvalue-or-callbyreference-neither/


# ## Define a new filter f and convolve with r

# In[79]:


f=np.zeros([5,5])
f[4,4]=1
r=ims[:,:,0]

r2=cv2.filter2D(r,-1,f,borderType=cv2.BORDER_CONSTANT)

plt.imshow(r2)


# ## apply Canny edge detector on r

# In[80]:


edge=cv2.Canny(r,100,200)

plt.imshow(edge,cmap='gray')


# # Video capture from webcam

# In[19]:


import cv2
import platform

cap=cv2.VideoCapture(0)

while (True):
    
    ret,frame=cap.read()
    
    cv2.namedWindow("camera",cv2.WND_PROP_FULLSCREEN)
    cv2.setWindowProperty("camera",cv2.WND_PROP_FULLSCREEN,cv2.WINDOW_FULLSCREEN)
    cv2.imshow('camera',frame)
    
    if cv2.waitKey(1) &0xFF == ord('q'): # press q or ESC to quit. You probably need to hit the screen first
        break

        
cap.release()
cv2.destroyAllWindows()
    


# # Edge detection with webcam input

# In[22]:


import cv2
import platform

cap=cv2.VideoCapture(0)

while (True):
    
    ret,frame=cap.read()
    
    cv2.namedWindow("camera",cv2.WND_PROP_FULLSCREEN)
    cv2.setWindowProperty("camera",cv2.WND_PROP_FULLSCREEN,cv2.WINDOW_FULLSCREEN)
    frame=cv2.cvtColor(frame,cv2.COLOR_RGB2GRAY)
    frame=cv2.Canny(frame,50,60)

    cv2.imshow('camera',frame)
    
    if cv2.waitKey(1) &0xFF == ord('q'): # press q or ESC to quit. You probably need to hit the screen first
        break

        
cap.release()
cv2.destroyAllWindows()