Image processing

image-processing

asked 2013-03-14 14:39:31 +0200

beginner
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updated 2013-03-14 14:47:55 +0200

kcrisman
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Dear all, I have question about manipulating image in Sage. Here is some example.

import pylab
img=pylab.imread(DATA+'lena.png')

Img is now array with float elements. But I want to add some shapes on this image like circle, rectangle, polygon etc, but c=Circle, b=Rectangle and a=Polygon are object of some clases so if I want to do something like this show(img+c) or show(img+b) it is not allowed. Another question is: How I can put circle on my position (position is corner of image) because Img is array so I don't know where new row start.

Is there some simple way to do this?

Thank you in advance

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answered 2013-03-14 15:00:00 +0200

kcrisman
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I'd suggest using matrix_plot.

sage: import pylab
sage: from scipy import misc
sage: I = misc.lena()
sage: (matrix_plot(I)+circle((5,3),100)).show(ymax=500)

If you try this, you'll see that there are a couple bugs (?) that this unveils in how we compute limits; apparently no one has ever wanted to put a circle on an image before!

It's also possible to export images as matplotlib objects.

sage: C = circle((5,3),100)
sage: C.matplotlib()
sage: pylab.imshow(misc.lena())
<matplotlib.image.AxesImage at 0x1121f0310>

But someone else will have to answer how to combine those in native matplotlib, though it certainly isn't hard for anyone who uses mpl regularly.

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answered 2013-05-13 01:59:15 +0200

blueimage
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updated 2013-11-10 22:18:22 +0200

ppurka
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answered 2013-11-10 22:13:39 +0200

aclink
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updated 2013-11-10 22:18:04 +0200

ppurka
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answered 2013-03-14 15:59:08 +0200

beginner
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Thank you this example works, but what about if my image is not Lena.png (I put that like example). If I put something like this:

I=misc.imread(DATA+'myexample.png') and put the rest of Your code I got "TypeError: mat must be a Matrix or a two dimensional array".

My image is color image so it's 3D. How I can easy convert to 2D?

Thank you in advance!

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I suggest looking at http://matplotlib.org/users/image_tutorial.html In principle it shouldn't matter that it's color, as long as you use the right syntax (I note you have scipy.misc.imread, not pylab.imread).

kcrisman ( 2013-03-15 08:42:59 +0200 )edit

Thank you so much!!!

beginner ( 2013-03-15 18:05:06 +0200 )edit

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