I'm going to wait for the lazy fill brush to be implemented and then build off that work, since there should be many similarities between the way those tools function under the hood.
The magnetic lasso tool was lost in the port to Qt4. The code was in bad shape, but is now in working condition. Before it is possible to add to Krita as an experimental feature, the magnetic lasso tool will need:
- New icons
- New cursors
- Redesign the on-screen feedback
Some of the changes need to hook into existing Krita API. Anyone know more about these?
- Hook in with the pre-existing filtering classes, e.g. KisSobelFilter, Gaussian Filter.
- Store pre-computed data caches, e.g. pre-blurring, edge gradients, color space transformations, IFT, watershed regions / superpixels...
- Subpixel accessors for e.g. computing the edge strength interpolated between pixels.
- Using signals&slots to keep cache up to date. (If someone asks for it)
- Parallel processing (Get a single threaded approach working first, worry about this later)
Finally the tool itself will have to be resdesigned. This is completely open. It barely even has to look like a magnetic lasso. Doesn't even have to be called a magnetic lasso! "Refine edge," "Paint selection," "Smart Contours"
Edge / Live-wire methods: somewhat similar to the existing tool
- [[http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.89.2987&rep=rep1&type=pdf | Intelligent Scissors (1998) ]] The classic, implemented by GIMP
- [[ http://wcours.gel.ulaval.ca/2013/a/GIF7002/default/5notes/diapositives/pdf_A13/lectures%20supplementaires/C08e.pdf | Edge and line oriented contour detection: State of the art (2011) ]]
- [[http://www.ic.unicamp.br/~afalcao/mo815-grafos/a13.pdf | Live Wire On The Fly (2000) ]] Super fast, perhaps also straightforward to implement
- [[http://www.math.lsa.umich.edu/~esedoglu/Papers_Preprints/xbresson_gmac_jmiv05.pdf | Fast global minimization of the active contour/ snake model (2005) ]]
- [[ https://hal-upec-upem.archives-ouvertes.fr/hal-00622510/document | Power Watersheds: A Unifying Graph Based Optimization Framework (2012) ]]
- [[ http://www.cb.uu.se/~filip/ImageProcessingUsingGraphs/schedule.html | Image Processing Using Graphs ]] Lecture notes. Lecture 7 focuses on live wire methods. Several lectures on computation. Another note [[http://www.ic.unicamp.br/~afalcao/talks/ift09.pdf | here]].
- [[ http://arxiv.org/abs/1406.5549 | Fast Edge Detection Using Structured Forests]]
- [[ http://web.mit.edu/phillipi/pmi-boundaries/ | Crisp Boundary Detection Using Pointwise Mutual Information ]]
- [[ http://arxiv.org/pdf/1406.6558v2.pdf | Neural Network Nearest Neighbor Fields for Image Transforms]]
- [[ http://arxiv.org/abs/1412.1123 | DeepEdge (2014) ]]
Graph cuts: fast approximate global methods well adapted for interactive use
- [[ http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.297.9821&rep=rep1&type=pdf | Image Segmentation by Iterated Region Merging with Localized Graph Cuts (2011) ]] Results look great, but speed?
- [[ http://research-srv.microsoft.com/en-us/um/people/jiansun/papers/PaintSelection_SIGGRAPH09.pdf | Paint Selection (2009) ]]
- [[ http://medialab.sjtu.edu.cn/teaching/DIP/Projects/chapter_seg/SurveyGraphImageSegmentation.pdf | A survey of graph theoretical approaches to image segmentation (2013) ]] Authors ultimately recommend their own paper, listed above.
- [[ http://www.math.wvu.edu/~kcies/Other/ElectronicReprints/106.FCvsGCReprint.pdf | Fuzzy Connectedness Image Segmentation: A Linear-Time Algorithm (2012) ]] Supposedly a new, fast algorithm is buried under the math?
Level sets: robust class of global methods, numerically slow
- [[https://vision.in.tum.de/_media/spezial/bib/cremers_rousson_deriche_ijcv07.pdf | A Review of Statistical Approaches to Level Set Segmentation (2007) ]] Overview paper, motivates level set methods
- [[http://jgmalcolm.com/pubs/malcolm_lsdm.pdf | Fast approximate surface evolution in arbitrary dimension (2008)]]
- [[ http://www.ntu.edu.sg/home/asjfcai/TIP-07763-2011_2column.pdf | Robust Interactive Segmentation using Convex Active Contours (2011) ]] Champion performer, though speed is a concern
- [[http://ocw.mit.edu/courses/mathematics/18-336-numerical-methods-for-partial-differential-equations-spring-2009/readings/MIT18_336s09_read04_levelsetpres.pdf | Level set method - MIT 336 lecture notes (2009) ]]
- [[http://www.robots.ox.ac.uk/~varun/research/gsc.pdf | Geodesic star convexity (2010) ]] Code available [[http://www.robots.ox.ac.uk/~vgg/software/iseg/ | here]]
- [[ http://bigwww.epfl.ch/publications/bernard0901.pdf | Variational B-Spline Level Set (2009) ]] Returning B-splines as an output could be nice