SPOQ: norm ratio sparsity restoration (how I discovered sparsity and stopped worrying about it)

[TL;DR] How I discovered sparsity and stopped worrying about it This is a journey into sparsity. The story started in 2009, in the South of France, and the nice island of Porquerolles. Here, clear blue water. France, Porquerolles, plage Notre-Dame There was a workshop organized in June called Porquerolles 2019: Approximation and optimization in image restoration and reconstruction . A bunch of first class researchers were there: Amel Benazza-Benyahia, Jérôme Bolte, Antonin Chambolle, Caroline Chaux, Philippe Ciuciu, Albert Cohen, Patrick Louis Combettes, Claude Comtat, Christine de Mol, Alvaro R. De Pierro, Michel Defrise, Ron DeVore, Jalal Fadili, Mario Figueiredo, Massimo Fornasier, Jacques Froment, Yves Goussard, Gabor Herman, Jérome Idier, Dirk Lorenz, Russell Luke, Francois Malgouyres, Pierre Maréchal, Ali Mohammad-Djafari, Stanley Osher, Valérie Perrier, Jean-Christophe Pesquet, Gabriel Peyré, Aleksandra Pizurica, Andrew Reader, Elena Resmerita, Marc Sig