Jasper van de Gronde
 room number: 491 (Bernoulliborg, building 5161)
 email: j.j.van.de.gronde rug.nl
Research interests
I am interested in all sorts of image processing topics, including compressed sensing, linear and morphological filters, and deep learning, with a special interest in applications on large/highdimensional and nonscalar data. Making proper use of vector or tensorvalued data, possibly as an intermediate step, also interests me greatly, as does the interplay between (mostly) linear approaches and morphological approaches. My PhD thesis was on morphological operators for tensor images, exploring shape and structure in movement and direction dependence. I defended my thesis on 30 June 2015, and am currently a postdoc.
Tensor images (or volumes) are just like ordinary images or volumes, except that at each point we have a vector or matrix (tensors are essentially a generalization of vectors and matrices). To visualize a tensor image with matrices at each position, we typically use "glyphs": for each position a small glyph is drawn whose shape represents the matrix (S). The glyph is often a unit sphere deformed in such a way that each vector v on the unit sphere is given the magnitude v.(S.v). Below you can interact with a live demonstration of this technique (requires a WebGL capable browser, I recommend Firefox, and possibly some patience):


In this case, the matrices describe stresses at atomic positions in a nanowire (courtesy of S.S.R. Saane, Micromechanics group, RuG). Blue shows positive values(/radii), while orange shows negative values. 
Demos
Apart from the rendering above, here is some more code you can try out both in the browser and using Node.js:
 Groupinvariant frames for colour morphology. This tries to make "false" colours much less objectionable by using group invariant frames (and thereby operators).
 Frames for Tensor Field Morphology. Uses rotationinvariant frames to apply morphological filters to structure tensors.
 Pathbased mathematical morphology on tensor fields. Path openings on general directed acyclic graphs derived from tensor fields.
 Efficient and Robust Path Openings using the ScaleInvariant Rank Operator. Generalized path openings on binary images and greyscale sequences.
There are also some demos that can only be run offline:
 Groupinvariant colour morphology based on frames. Similar to other previous demo concerning groupinvariant frames, but also has code for performing a simple classification task. (Python)
 Frames, the Loewner order and eigendecomposition for morphological operators on tensor fields. Demonstration of various methods for computing morphological filters on tensor fields. (Python)
 Fast Computation of Greyscale Path Openings. Novel algorithm for computing greyscale path openings on images. (C++)
 Tensorial Orientation Scores. Computes tensorial orientation scores. (Mathematica)
 Generalized Morphology using Sponges. Simple example of filtering anglevalued signals. (Mathematica)
Various projects not (necessarily) associated with a particular publication can be found on Github (also see the SciJS repository).
Further information and links
I maintain a bibliography of work done on both colour morphology and tensor morphology (note that I'm not too strict about what classifies as "colour" morphology). I try to subclassify (using tags) papers based on what kind of method they use. If you feel anything is missing or wrong, please let me know.
An interesting (informal) discussion of the problem of finding a total order for colours can be found here. Note that most of the approaches discussed there indeed correspond to actual algorithms that have been tried in mathematical morphology (and the overview is even fairly, although not entirely, complete). In particular, people have experimented with methods similar to the Hilbert curve approach (Chanussot1998), as well as the travelling salesman approach (Florez2005, Chevallier2014). But note that Chevallier has shown that any total order is necessarily discontinuous when computing joins and meets (this is part of the reason why much of my thesis is focussed on making partial orders more palatable).
Although I tend to talk about product orders and lexicographical orders, there are many more related concepts, as well as different terms for the same concepts. To clarify, I have made a short summary of different terms and in which context they are used.
Publications
 Ji, Chengtao, Gronde, Jasper J. van de, Maurits, Natasha M. and Roerdink, Jos B. T. M (2019) Visual Exploration of Dynamic Multichannel EEG Coherence Networks.. . (URL) (BibTeX)
 Soancatl Aguilar, Venustiano, van de Gronde, Jasper J., Lamoth, Claudine J. C., Maurits, Natasha M. and Roerdink, Jos B. T. M. (2018) Assessing Postural Control Performance during Exergaming based on Speed and Curvature of Body Movements.. . Attach:pdf.gif Δ Δ (BibTeX)
 Soancatl Aguilar, Venustiano, J. van de Gronde, Jasper, J. C. Lamoth, Claudine, van Diest, Mike, M. Maurits, Natasha and B. T. M. Roerdink, Jos (2017) Visual Data Exploration for Balance Quantification in RealTime During Exergaming.. . (URL) (BibTeX)
 Chengtao Ji and Jasper J. van de Gronde and Natasha M. Maurits and Jos B. T. M. Roerdink (2017) Visualizing and Exploring Dynamic Multichannel EEG Coherence Networks. In {VCBM} 17: Eurographics Workshop on Visual Computing for Biology and Medicine, Bremen, Germany, September 78, 2017.. Eurographics Association, pages 6372. Honorable Mention Award. (URL) (BibTeX)
 Soancatl Aguilar, Venustiano, van de Gronde, Jasper J., Maurits, Natasha M., Lamoth, Claudine C. J. C. and Roerdink, Jos B. T. M. (2016) Curvature and Speed for Balance Quantification During Exergaming. In Proceedings of the 9th International Conference on Motion in Games. New York, NY, USA. ACM, pages 201202. (URL) (BibTeX)
 Soancatl Aguilar, Venustiano, van de Gronde, J. J. and Lamoth, C. J. C., Maurits, N. M. and Roerdink, Jos B. T. M. (2016) Visual Data Exploration for Balance Quantification During Exergaming. In EuroVis 2016  Posters. Groningen. The Eurographics Association, pages 2527. (URL) (BibTeX)
 Ji, Chengtao, van de Gronde, Jasper J. and Maurits, Natasha M. and Roerdink, Jos B. T. M. (2016) Tracking and Visualizing Dynamic Structures in Multichannel EEG Coherence Networks. In EuroVis 2016  Posters.. The Eurographics Association, pages 2830. (URL) (BibTeX)
 Ji, Chengtao, van de Gronde, Jasper J. and Maurits, Natasha M. and Roerdink, Jos B. T. M. (2016) Exploration of Complex Dynamic Structures in Multichannel EEG Coherence Networks via Information Visualization Techniques. In CCS 2016  Posters.. (BibTeX)
 van de Gronde, Jasper J., Offringa, AndrĂ© R. and Roerdink, Jos B. T. M. (2016) Efficient and Robust Path Openings using the ScaleInvariant Rank Operator.. . Attach:pdf.gif Δ Δ (URL) (BibTeX)
 Schubert, Herman, van de Gronde, Jasper J. and Roerdink, Jos B. T. M. (2016) Efficient Computation of Greyscale Path Openings.. . Attach:pdf.gif Δ Δ (URL) (BibTeX)
 van de Gronde, Jasper J. and Roerdink, Jos B. T. M. (2016) Generalized Morphology using Sponges.. . Attach:pdf.gif Δ Δ (URL) (BibTeX)
 van de Gronde, Jasper J. (2015) Beyond Scalar Morphology. PhD thesis. (URL) (BibTeX)
 van de Gronde, Jasper J. (2015) Tensorial Orientation Scores. In Computer Analysis of Images and Patterns.. Springer International Publishing, pages 783794. Attach:pdf.gif Δ Δ (URL) (BibTeX)
 van de Gronde, Jasper J. and Roerdink, Jos B. T. M. (2015) Sponges for Generalized Morphology. In Mathematical Morphology and Its Applications to Signal and Image Processing. (Benediktsson, J\'on Atli, Chanussot, Jocelyn, Najman, Laurent and Talbot, Hugues, Eds.) Springer International Publishing, pages 351362. Attach:pdf.gif Δ Δ (BibTeX)
 van de Gronde, Jasper J., Lysenko, Mikola and Roerdink, Jos B. T. M. (2015) PathBased Mathematical Morphology on Tensor Fields. In Visualization and Processing of Higher Order Descriptors for MultiValued Data. (Hotz, Ingrid and Schultz, Thomas, Eds.) Springer International Publishing, pages 109127. (URL) (BibTeX)
 van de Gronde, Jasper J., Schubert, Herman R. and Roerdink, Jos B. T. M. (2015) Fast Computation of Greyscale Path Openings. In Mathematical Morphology and Its Applications to Signal and Image Processing. (Benediktsson, J\'on Atli, Chanussot, Jocelyn, Najman, Laurent and Talbot, Hugues, Eds.) Springer International Publishing, pages 621632. Attach:pdf.gif Δ Δ (URL) (BibTeX)
 van de Gronde, Jasper J. and Roerdink, Jos B. T. M. (2014) GroupInvariant Colour Morphology Based on Frames.. . Attach:pdf.gif Δ Δ (URL) (BibTeX)
 van de Gronde, Jasper J. and Roerdink, Jos B. T. M. (2014) Frames, the Loewner order and eigendecomposition for morphological operators on tensor fields.. . Attach:pdf.gif Δ Δ (URL) (BibTeX)
 van de Gronde, Jasper J., Wilkinson, Michael H. F. and Roerdink, Jos B. T. M. (2013) Rotationinvariant morphological filtering of tensor fields using frames. In Poster session of the National ICT.OPEN (Eindhoven). nov. Attach:pdf.gif Δ Δ (BibTeX)
 van de Gronde, Jasper J. and Roerdink, Jos B. T. M. (2013) GroupInvariant Frames for Colour Morphology. In ASCI.OPEN (Eindhoven). nov. (BibTeX)
 van de Gronde, Jasper J. (2013) Web Graphics for Science. In HTML5 Developer Conference. oct. (URL) (BibTeX)
 van de Gronde, Jasper J. and Roerdink, Jos B. T. M. (2013) Frames for Tensor Field Morphology. In Geometric Science of Information. (Frank Nielsen and Fr\'ed\'eric Barbaresco, Eds.) Springer Berlin Heidelberg, pages 527534. Attach:pdf.gif Δ Δ (URL) (BibTeX)
 van de Gronde, Jasper J. and Roerdink, Jos B. T. M. (2013) GroupInvariant Frames for Colour Morphology. In Mathematical Morphology and Its Applications to Signal and Image Processing. (Luengo Hendriks, Cris L., Borgefors, Gunilla and Strand, Robin, Eds.) Springer Berlin Heidelberg, pages 267278. Attach:pdf.gif Δ Δ (URL) (BibTeX)
 van de Gronde, Jasper J., Wilkinson, Michael H.F. and Roerdink, Jos B.T.M. (2012) Making computers see tensors using mathematical morphology. In Poster session of the National ICT.OPEN (Rotterdam). oct. Attach:pdf.gif Δ Δ (BibTeX)
 A. R. Offringa and J. J. van~de~Gronde and J. B. T. M. Roerdink (2012) A morphological algorithm for improving radiofrequency interference detection.. . (BibTeX)
 Jasper van de Gronde (2010) A High Quality Solver for Diffusion Curves. Master's thesis. Attach:pdf.gif Δ Δ (URL) (BibTeX)