	US 12,277,737 B2
	Method for encoding a digital image in order to compress same
Amaury Darsch, Lorient (FR); and Lucas Clarté, Gagny (FR)
Assigned to SHADOW, Paris (FR)
Appl. No. 17/757,532
Filed by SHADOW, Paris (FR)
PCT Filed Dec. 16, 2020, PCT No. PCT/FR2020/052464 § 371(c)(1), (2) Date Jun. 16, 2022, PCT Pub. No. WO2021/123617, PCT Pub. Date Jun. 24, 2021.
Claims priority of application No. 1914826 (FR), filed on Dec. 19, 2019.
Prior Publication US 2023/0009035 A1, Jan. 12, 2023
Int. Cl. G06T 9/00 (2006.01); G06V 10/44 (2022.01); H04N 19/90 (2014.01)

CPC G06T 9/00 (2013.01) [H04N 19/90 (2014.11); G06V 10/44 (2022.01)]

12 Claims

1. A method for encoding a digital image formed by a set of N pixels (p_ij) for compression thereof, the digital image being defined as a cloud of N points (i, j, f_ij), designated as vertices (v_k), associating the set of N pixels (p_ij) with a scalar intensity value (f_ij), the method comprising the following steps:

a) ordering N vertices (v_k) in increasing order of scalar intensity values (f_ij) in a vertex table, wherein the ordering step comprises applying a discrimination rule so as to order, in the vertex table, two vertices having the same scalar intensity value;

b) initializing an iteration index i and a class index c to 0, initializing a starting simplicial complex (K₀) to an empty set and repeating the sequence of the following operations until the iteration index i reaches N:

incrementing the iteration index i;

extracting the vertex of rank i (v_i) from the vertex table and checking whether the vertex of rank i (v_i) is in the neighborhood of a vertex comprised in the simplicial complex of rank i−1 (K_i−1); and

if no vertex of the simplicial complex of rank i (K_i) is in the neighborhood of the vertex of rank i (v_i), incrementing the rank of class c, forming the simplicial complex of rank i (K_i) by adding a new class (C_c) composed of the vertex of rank i (v_i) to the simplicial complex of rank i−1 (K_i−1), and assigning rank c to the new class (C_c);

if at least one vertex of a single class of the simplicial complex of rank i (K_i) is in the neighborhood of the vertex of rank i (v_i), forming the simplicial complex of rank i (K_i) by adding the vertex of rank i (v_i) to the simplicial complex of rank i−1 (K_i−1) in this one class;

if several vertices of a plurality of classes of the simplicial complex of rank i (K_i) are in the neighborhood of the vertex of rank i (v_i), forming the simplicial complex of rank i (K_i) by grouping together, in the simplicial complex of rank i−1 (K_i−1), the vertices forming this plurality of classes and the vertex of rank i (v_i) in the class of lowest rank and forming a persistence pair comprising:

i. the first vertex (v_ic) corresponding to the lowest rank vertex in the lowest rank class of the plurality of classes of the simplicial complex of rank i (K_i), this rank being called the appearance rank of the persistence pair (ic); and

ii. the second vertex (v_id) corresponding to the vertex of rank of index i (v_i), this rank i being called the disappearance rank of the persistence pair (id); and

in a decimation step, calculating, for each persistence pair (v_ic, v_id) identified, a lifetime associated with the persistence pair (v_ic, v_id) calculated as a difference between the disappearance rank of the persistence pair (id) and the appearance rank of the persistence pair (ic), and retaining, in a restricted list, some of the persistence pairs (v_ic, v_id) exhibiting the longest lifetimes;

the encoded digital image comprising at least some pixels (p_ij) corresponding to the vertices constituting the persistence pairs (v_ic, v_id) of the restricted list.