Tag: Python

Preventing Windows OS from sleeping while your python code runs

- by mahmood 
class WindowsInhibitor:
    '''Prevent OS sleep/hibernate in windows; code from:
    https://github.com/h3llrais3r/Deluge-PreventSuspendPlus/blob/master/preventsuspendplus/core.py
    API documentation:
    https://msdn.microsoft.com/en-us/library/windows/desktop/aa373208(v=vs.85).aspx'''
    ES_CONTINUOUS = 0x80000000
    ES_SYSTEM_REQUIRED = 0x00000001

    def __init__(self):
        pass

    def inhibit(self):
        import ctypes
        print("Preventing Windows from going to sleep")
        ctypes.windll.kernel32.SetThreadExecutionState(
            WindowsInhibitor.ES_CONTINUOUS | \
            WindowsInhibitor.ES_SYSTEM_REQUIRED)

    def uninhibit(self):
        import ctypes
        print("Allowing Windows to go to sleep")
        ctypes.windll.kernel32.SetThreadExecutionState(
            WindowsInhibitor.ES_CONTINUOUS)
import os

osSleep = None
# in Windows, prevent the OS from sleeping while we run
if os.name == 'nt':
    osSleep = WindowsInhibitor()
    osSleep.inhibit()

# do slow stuff

if osSleep:
    osSleep.uninhibit()

References
https://trialstravails.blogspot.com/2017/03/preventing-windows-os-from-sleeping.html

Basic NumPy for working with OpenCV

- by mahmood

Create an array from a list

my_list = [1, 2, 3]
my_array = np.array(my_list)

Create an array with arrange

my_array = np.arange(0, 10)
my_array2 = np.arange(0, 10, 2) # with step 2

Create an array with zeros

my_array = np.zeros((2, 3)) # default type if float
my_array2 = np.zeros((2, 3), np.int32) # with type int

Create an array with ones

my_array = np.ones((10, 8), np.int32)

Create an array from random

np.random.seed(101)
array1 = np.random.randint(0, 100, 10)
array2=np.random.randint(0,100,10)

Max, Min, Mean

np.random.seed(101)
array1 = np.random.randint(0, 100, 10)
print(array1.max())
print(array1.argmax()) # index of max value
print(array1.min())
print(array1.argmin()) # index of min value
print(array1.mean())

Indexing an array

matrix = np.arange(0, 100).reshape(10, 10)
print(matrix)

print(matrix[2,3])

row = 1
col = 4
print(matrix[row,col])

Manipulating an array

matrix = np.arange(0, 100).reshape(10, 10)
print(matrix)

matrix[0:3, 0:3] = 0
print(matrix)

Copying an array

matrix: np.ndarray = np.arange(0, 100).reshape(10, 10)
print(matrix)

matrix2 = matrix.copy()
matrix2[0:3, 0:3] = 0
print(matrix2)

Slicing an array

matrix = np.arange(0, 100).reshape(10, 10)

print(matrix[1, :])  # whole row 1
print(matrix[:, 1])  # whole col 1
print(matrix[1, 1:4])  # row 1 from col 1 to 4
print(matrix[1:4, 1])  # col 1 from row 1 to 4

new_matrix: np.ndarray = matrix[1, :]
print(new_matrix.reshape(5, 2))

Reshaping an array

np.random.seed(101)
array1 = np.random.randint(0, 100, 10)
print(array1)
print(array1.shape)

array2 = array1.reshape((2, 5))
print(array2)
print(array2.shape)

References
https://www.tutorialspoint.com/numpy/index.htm

Image Operations with OpenCV Python

- by mahmood

Read Pixel

import cv2
import numpy as np
import pprint

image = cv2.imread('cow.jpg',cv2.IMREAD_COLOR)
pixel= image[55,55]
pprint.pprint(pixel)

Change Pixel

import cv2
import numpy as np
import pprint

image = cv2.imread('cow.jpg', cv2.IMREAD_COLOR)
image[55, 55] = [255, 255, 255]
pixel = image[55, 55]
pprint.pprint(pixel)

Change the color of Region of Image

import cv2
import numpy as np
import pprint

image = cv2.imread('cow.jpg', cv2.IMREAD_COLOR)
image[150:200, 100:150] = [255, 255, 255]
cv2.imshow("image", image)
cv2.waitKey(0)
cv2.destroyAllWindows()

Image Characteristics 

import cv2
import numpy as np
import pprint

image = cv2.imread('cow.jpg', cv2.IMREAD_COLOR)
print(image.shape)
print(image.size)
print(image.dtype)

Copy Paste Region

import cv2
import numpy as np
import pprint

image = cv2.imread('cow.jpg', cv2.IMREAD_COLOR)

watch_face = image[200:250,107:194]
image[0:50,0:87] = watch_face

cv2.imshow('image',image)
cv2.waitKey(0)
cv2.destroyAllWindows()

References
https://pythonprogramming.net/image-operations-python-opencv-tutorial/
https://www.youtube.com/watch?v=1pzk_DIL_wo&list=PLQVvvaa0QuDdttJXlLtAJxJetJcqmqlQq&index=4
https://github.com/mhdr/OpenCV/tree/master/004