Filling Array is Slow











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The code below is a project that I am working on to eventually analyze some images but right now I am purely trying to read an image and convert it to black and white. The input should be either white or something else which would end up as black so it is easy to check for this.



import matplotlib.pyplot as plt
import matplotlib.image as mpimg
import numpy as np

img = mpimg.imread('./Training/Image1.png')

imgplot = plt.imshow(img)

width = img.shape[1]
height = img.shape[0]

def generateArray():
arr =
for y in range(img.shape[0]):
arr.append()
for x in range(img.shape[1]):
if img[y][x][0] != 1:
arr[y].append(1)
else:
arr[y].append(0)
return arr

arr = generateArray()

plt.show()


To be clear, I desire to create an array arr that contains either a 0 if the corresponding pixel in the inputted image is white or 1 if it is anything other than white.



I am somewhat of a beginner with Python but I am confused as to why this code takes so long to run (>19 seconds on my older mac). Is there something that I am missing that would speed it up significantly?










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    up vote
    0
    down vote

    favorite












    The code below is a project that I am working on to eventually analyze some images but right now I am purely trying to read an image and convert it to black and white. The input should be either white or something else which would end up as black so it is easy to check for this.



    import matplotlib.pyplot as plt
    import matplotlib.image as mpimg
    import numpy as np

    img = mpimg.imread('./Training/Image1.png')

    imgplot = plt.imshow(img)

    width = img.shape[1]
    height = img.shape[0]

    def generateArray():
    arr =
    for y in range(img.shape[0]):
    arr.append()
    for x in range(img.shape[1]):
    if img[y][x][0] != 1:
    arr[y].append(1)
    else:
    arr[y].append(0)
    return arr

    arr = generateArray()

    plt.show()


    To be clear, I desire to create an array arr that contains either a 0 if the corresponding pixel in the inputted image is white or 1 if it is anything other than white.



    I am somewhat of a beginner with Python but I am confused as to why this code takes so long to run (>19 seconds on my older mac). Is there something that I am missing that would speed it up significantly?










    share|improve this question
























      up vote
      0
      down vote

      favorite









      up vote
      0
      down vote

      favorite











      The code below is a project that I am working on to eventually analyze some images but right now I am purely trying to read an image and convert it to black and white. The input should be either white or something else which would end up as black so it is easy to check for this.



      import matplotlib.pyplot as plt
      import matplotlib.image as mpimg
      import numpy as np

      img = mpimg.imread('./Training/Image1.png')

      imgplot = plt.imshow(img)

      width = img.shape[1]
      height = img.shape[0]

      def generateArray():
      arr =
      for y in range(img.shape[0]):
      arr.append()
      for x in range(img.shape[1]):
      if img[y][x][0] != 1:
      arr[y].append(1)
      else:
      arr[y].append(0)
      return arr

      arr = generateArray()

      plt.show()


      To be clear, I desire to create an array arr that contains either a 0 if the corresponding pixel in the inputted image is white or 1 if it is anything other than white.



      I am somewhat of a beginner with Python but I am confused as to why this code takes so long to run (>19 seconds on my older mac). Is there something that I am missing that would speed it up significantly?










      share|improve this question













      The code below is a project that I am working on to eventually analyze some images but right now I am purely trying to read an image and convert it to black and white. The input should be either white or something else which would end up as black so it is easy to check for this.



      import matplotlib.pyplot as plt
      import matplotlib.image as mpimg
      import numpy as np

      img = mpimg.imread('./Training/Image1.png')

      imgplot = plt.imshow(img)

      width = img.shape[1]
      height = img.shape[0]

      def generateArray():
      arr =
      for y in range(img.shape[0]):
      arr.append()
      for x in range(img.shape[1]):
      if img[y][x][0] != 1:
      arr[y].append(1)
      else:
      arr[y].append(0)
      return arr

      arr = generateArray()

      plt.show()


      To be clear, I desire to create an array arr that contains either a 0 if the corresponding pixel in the inputted image is white or 1 if it is anything other than white.



      I am somewhat of a beginner with Python but I am confused as to why this code takes so long to run (>19 seconds on my older mac). Is there something that I am missing that would speed it up significantly?







      python performance






      share|improve this question













      share|improve this question











      share|improve this question




      share|improve this question










      asked 11 mins ago









      dalearn

      1113




      1113



























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