Plotting positive and negative pixels of image separately on subplots











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Suppose have an image like this, that consists of two images, 1 and 6 which are kind of superimposed on each other, if you look closely at it.



So, I need to visualize each of these digits separately by having all positive pixels of original image in one image, and all negative pixels in the second one. Is there any way to achieve that in python using matplotlib.pyplot without messing up with the structure of the image? Basically, I need all the white color pixels to be plotted separately from the black color pixels.
enter image description here










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    up vote
    0
    down vote

    favorite












    Suppose have an image like this, that consists of two images, 1 and 6 which are kind of superimposed on each other, if you look closely at it.



    So, I need to visualize each of these digits separately by having all positive pixels of original image in one image, and all negative pixels in the second one. Is there any way to achieve that in python using matplotlib.pyplot without messing up with the structure of the image? Basically, I need all the white color pixels to be plotted separately from the black color pixels.
    enter image description here










    share|improve this question
























      up vote
      0
      down vote

      favorite









      up vote
      0
      down vote

      favorite











      Suppose have an image like this, that consists of two images, 1 and 6 which are kind of superimposed on each other, if you look closely at it.



      So, I need to visualize each of these digits separately by having all positive pixels of original image in one image, and all negative pixels in the second one. Is there any way to achieve that in python using matplotlib.pyplot without messing up with the structure of the image? Basically, I need all the white color pixels to be plotted separately from the black color pixels.
      enter image description here










      share|improve this question













      Suppose have an image like this, that consists of two images, 1 and 6 which are kind of superimposed on each other, if you look closely at it.



      So, I need to visualize each of these digits separately by having all positive pixels of original image in one image, and all negative pixels in the second one. Is there any way to achieve that in python using matplotlib.pyplot without messing up with the structure of the image? Basically, I need all the white color pixels to be plotted separately from the black color pixels.
      enter image description here







      python matplotlib image-processing plot pixel






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      share|improve this question










      asked Nov 15 at 1:42









      ViniLL

      196




      196
























          1 Answer
          1






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          You may set all values above or below some threshold to nan, such that they won't appear in the final image.



          The following code leaves out the range between 0.4 and 0.6 completely. The yellow background is chosen to show that there are no pixels in that area.



          import numpy as np
          import matplotlib.pyplot as plt

          img = plt.imread("grayscaleimage.png")[:,:,0]

          white = np.copy(img)
          white[white<0.6] = np.nan

          dark = np.copy(img)
          dark[dark>0.4] = np.nan

          fig = plt.figure()
          ax0 = fig.add_subplot(211)
          ax1 = fig.add_subplot(223)
          ax2 = fig.add_subplot(224)

          ax0.imshow(img, vmin=0, vmax=1, cmap="Greys")
          ax1.imshow(white, vmin=0, vmax=1, cmap="Greys")
          ax2.imshow(dark, vmin=0, vmax=1, cmap="Greys")

          for ax in (ax1,ax2):
          ax.set_facecolor("gold")

          plt.show()


          enter image description here






          Here is the test image used in the above:
          enter image description here (right click, save as...)




          share|improve this answer























          • Thanks a lot, it worked pretty well! I had to change some values though, but I got the point. Could you also share where did you get your testing image? it looks much sharper and it is very relevant to my ML perceptron algorithm that I am implementing
            – ViniLL
            Nov 15 at 7:42










          • I added the test image. It's created via inkscape by placing a white 1 and a black 6 on gray background.
            – ImportanceOfBeingErnest
            Nov 15 at 13:40










          • Ok got you, thanks.
            – ViniLL
            Nov 15 at 18:32











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          1 Answer
          1






          active

          oldest

          votes








          1 Answer
          1






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes








          up vote
          0
          down vote



          accepted










          You may set all values above or below some threshold to nan, such that they won't appear in the final image.



          The following code leaves out the range between 0.4 and 0.6 completely. The yellow background is chosen to show that there are no pixels in that area.



          import numpy as np
          import matplotlib.pyplot as plt

          img = plt.imread("grayscaleimage.png")[:,:,0]

          white = np.copy(img)
          white[white<0.6] = np.nan

          dark = np.copy(img)
          dark[dark>0.4] = np.nan

          fig = plt.figure()
          ax0 = fig.add_subplot(211)
          ax1 = fig.add_subplot(223)
          ax2 = fig.add_subplot(224)

          ax0.imshow(img, vmin=0, vmax=1, cmap="Greys")
          ax1.imshow(white, vmin=0, vmax=1, cmap="Greys")
          ax2.imshow(dark, vmin=0, vmax=1, cmap="Greys")

          for ax in (ax1,ax2):
          ax.set_facecolor("gold")

          plt.show()


          enter image description here






          Here is the test image used in the above:
          enter image description here (right click, save as...)




          share|improve this answer























          • Thanks a lot, it worked pretty well! I had to change some values though, but I got the point. Could you also share where did you get your testing image? it looks much sharper and it is very relevant to my ML perceptron algorithm that I am implementing
            – ViniLL
            Nov 15 at 7:42










          • I added the test image. It's created via inkscape by placing a white 1 and a black 6 on gray background.
            – ImportanceOfBeingErnest
            Nov 15 at 13:40










          • Ok got you, thanks.
            – ViniLL
            Nov 15 at 18:32















          up vote
          0
          down vote



          accepted










          You may set all values above or below some threshold to nan, such that they won't appear in the final image.



          The following code leaves out the range between 0.4 and 0.6 completely. The yellow background is chosen to show that there are no pixels in that area.



          import numpy as np
          import matplotlib.pyplot as plt

          img = plt.imread("grayscaleimage.png")[:,:,0]

          white = np.copy(img)
          white[white<0.6] = np.nan

          dark = np.copy(img)
          dark[dark>0.4] = np.nan

          fig = plt.figure()
          ax0 = fig.add_subplot(211)
          ax1 = fig.add_subplot(223)
          ax2 = fig.add_subplot(224)

          ax0.imshow(img, vmin=0, vmax=1, cmap="Greys")
          ax1.imshow(white, vmin=0, vmax=1, cmap="Greys")
          ax2.imshow(dark, vmin=0, vmax=1, cmap="Greys")

          for ax in (ax1,ax2):
          ax.set_facecolor("gold")

          plt.show()


          enter image description here






          Here is the test image used in the above:
          enter image description here (right click, save as...)




          share|improve this answer























          • Thanks a lot, it worked pretty well! I had to change some values though, but I got the point. Could you also share where did you get your testing image? it looks much sharper and it is very relevant to my ML perceptron algorithm that I am implementing
            – ViniLL
            Nov 15 at 7:42










          • I added the test image. It's created via inkscape by placing a white 1 and a black 6 on gray background.
            – ImportanceOfBeingErnest
            Nov 15 at 13:40










          • Ok got you, thanks.
            – ViniLL
            Nov 15 at 18:32













          up vote
          0
          down vote



          accepted







          up vote
          0
          down vote



          accepted






          You may set all values above or below some threshold to nan, such that they won't appear in the final image.



          The following code leaves out the range between 0.4 and 0.6 completely. The yellow background is chosen to show that there are no pixels in that area.



          import numpy as np
          import matplotlib.pyplot as plt

          img = plt.imread("grayscaleimage.png")[:,:,0]

          white = np.copy(img)
          white[white<0.6] = np.nan

          dark = np.copy(img)
          dark[dark>0.4] = np.nan

          fig = plt.figure()
          ax0 = fig.add_subplot(211)
          ax1 = fig.add_subplot(223)
          ax2 = fig.add_subplot(224)

          ax0.imshow(img, vmin=0, vmax=1, cmap="Greys")
          ax1.imshow(white, vmin=0, vmax=1, cmap="Greys")
          ax2.imshow(dark, vmin=0, vmax=1, cmap="Greys")

          for ax in (ax1,ax2):
          ax.set_facecolor("gold")

          plt.show()


          enter image description here






          Here is the test image used in the above:
          enter image description here (right click, save as...)




          share|improve this answer














          You may set all values above or below some threshold to nan, such that they won't appear in the final image.



          The following code leaves out the range between 0.4 and 0.6 completely. The yellow background is chosen to show that there are no pixels in that area.



          import numpy as np
          import matplotlib.pyplot as plt

          img = plt.imread("grayscaleimage.png")[:,:,0]

          white = np.copy(img)
          white[white<0.6] = np.nan

          dark = np.copy(img)
          dark[dark>0.4] = np.nan

          fig = plt.figure()
          ax0 = fig.add_subplot(211)
          ax1 = fig.add_subplot(223)
          ax2 = fig.add_subplot(224)

          ax0.imshow(img, vmin=0, vmax=1, cmap="Greys")
          ax1.imshow(white, vmin=0, vmax=1, cmap="Greys")
          ax2.imshow(dark, vmin=0, vmax=1, cmap="Greys")

          for ax in (ax1,ax2):
          ax.set_facecolor("gold")

          plt.show()


          enter image description here






          Here is the test image used in the above:
          enter image description here (right click, save as...)





          share|improve this answer














          share|improve this answer



          share|improve this answer








          edited Nov 15 at 13:39

























          answered Nov 15 at 2:40









          ImportanceOfBeingErnest

          123k10125201




          123k10125201












          • Thanks a lot, it worked pretty well! I had to change some values though, but I got the point. Could you also share where did you get your testing image? it looks much sharper and it is very relevant to my ML perceptron algorithm that I am implementing
            – ViniLL
            Nov 15 at 7:42










          • I added the test image. It's created via inkscape by placing a white 1 and a black 6 on gray background.
            – ImportanceOfBeingErnest
            Nov 15 at 13:40










          • Ok got you, thanks.
            – ViniLL
            Nov 15 at 18:32


















          • Thanks a lot, it worked pretty well! I had to change some values though, but I got the point. Could you also share where did you get your testing image? it looks much sharper and it is very relevant to my ML perceptron algorithm that I am implementing
            – ViniLL
            Nov 15 at 7:42










          • I added the test image. It's created via inkscape by placing a white 1 and a black 6 on gray background.
            – ImportanceOfBeingErnest
            Nov 15 at 13:40










          • Ok got you, thanks.
            – ViniLL
            Nov 15 at 18:32
















          Thanks a lot, it worked pretty well! I had to change some values though, but I got the point. Could you also share where did you get your testing image? it looks much sharper and it is very relevant to my ML perceptron algorithm that I am implementing
          – ViniLL
          Nov 15 at 7:42




          Thanks a lot, it worked pretty well! I had to change some values though, but I got the point. Could you also share where did you get your testing image? it looks much sharper and it is very relevant to my ML perceptron algorithm that I am implementing
          – ViniLL
          Nov 15 at 7:42












          I added the test image. It's created via inkscape by placing a white 1 and a black 6 on gray background.
          – ImportanceOfBeingErnest
          Nov 15 at 13:40




          I added the test image. It's created via inkscape by placing a white 1 and a black 6 on gray background.
          – ImportanceOfBeingErnest
          Nov 15 at 13:40












          Ok got you, thanks.
          – ViniLL
          Nov 15 at 18:32




          Ok got you, thanks.
          – ViniLL
          Nov 15 at 18:32


















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