2015-05-21 A simple pre-processing filter for image processing

When processing images, it is useful to avoid artifacts, in particular when you try to understand biological processes. In the past, I have used natural images (found on internet, grabbed from holiday pictures, ...) without controlling for possible problems.

In particular, digital pictures are taken on pixels which are most often placed on a rectangular grid. It means that if you rotate that image, you may lose information and distort it and thus get wrong results (even for the right algorithm!). Moreover, pictures have a border while natural scenes do not, unless you are looking at it through an aperture. Intuitively, this means that large objects would not fit on the screen and are less informative.

In computer vision, it is easier to handle these problems in Fourier space. There, an image (that we suppose square for simplicity) is transformed in a matrix of coefficients of the same size as the image. If you rotate the image, the Fourier spectrum is also rotated. But as you rotate the image, the information that was in the corners of the original spectrum may span outside the spectrum of the rotated image. Also, the information in the center of the spectrum (around low frequencies) is less relevant than the rest.

Here, we will try to keep as much information about the image as possible, while removing the artifacts related to the process of digitalizing the picture.

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2015-05-12 Extending Olshausens classical SparseNet

This is an old blog post, see the newer version in this post

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2015-05-06 Reproducing Olshausens classical SparseNet (part 2)

This is an old blog post, see the newer version in this post

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2015-05-05 Reproducing Olshausen's classical SparseNet (part 1)

This is an old blog post, see the newer version in this post

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2015-04-30 trame-sensorielle

L'installation Elasticité dynamique agit comme un filtre et génère de nouveaux espaces démultipliés, comme un empilement quasi infini d'horizons. Par principe de réflexion, la pièce absorbe l'image de l'environnement et accumule les points de vue ; le mouvement permanent requalifie continuellement ce qui est regardé et entendu.

Ce post utilise une image naturelle comme entrée d'une "trame sensorielle".

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2015-04-29 Moving from Mayavi to VisPy

A long standing dependency of MotionClouds is MayaVi. While powerful, it is tedious to compile and may discourage new users. We are trying here to show some attempts to do the same with the vispy library.

In another post, we tried to use matplotlib, but this had some limitations. Let's now try vispy, a scientific visualisation library in python using opengl.

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2015-04-26 MoviePy and python3

I was recently trying to embed a clip in a jupyter notebook using https://github.com/Zulko/moviepy, somthing that was working smoothly with python 2.7. After switching to python 3, this was not working anymore and left me scratcthing my head for a solution.

We live in a open-sourced world, so I filled an issue:

https://github.com/Zulko/moviepy/issues/160

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2015-04-10 elastic-force

L'installation Elasticité dynamique agit comme un filtre et génère de nouveaux espaces démultipliés, comme un empilement quasi infini d'horizons. Par principe de réflexion, la pièce absorbe l'image de l'environnement et accumule les points de vue ; le mouvement permanent requalifie continuellement ce qui est regardé et entendu.

On va maintenant utiliser des forces elastiques pour coordonner la dynamique des lames dans la trame.

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2015-04-01 homebrew cask : updating an existing cask

  • A new version of psychopy is out, I will try today to push that new infomation to http://caskroom.io/

  • I will base things on this previous contribution

  • set-up variables

    cd $(brew --prefix)/Library/Taps/caskroom/homebrew-cask
    github_user='meduz'
    project='psychopy'
    git remote -v
    

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2015-03-17 homebrew cask : updating an existing cask

  • A new version of owncloud is out, I will try today to push that new infomation to http://caskroom.io/

  • I will base things on this previous contribution

  • set-up variables

    cd $(brew --prefix)/Library/Taps/caskroom/homebrew-cask
    github_user='meduz'
    project='owncloud'
    git remote -v
    

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