1. A computer-implemented, raster to vector conversion method of an initial digital image comprising a pixel matrix, the method comprising: using a computer to perform the following steps: generating a digital image divided into polygons by dividing the initial digital image into a plurality of base triangles; defining a similarity criterion depending on at least one parameter; storing in memory said similarity criterion and said at least one parameter; and performing an iterative operation comprising: selecting at least a first polygon and a second polygon adjacent to each other and which satisfy said similarity criterion; merging said first polygon with said second polygon in order to generate a new digital image divided into polygons and comprising at least one new A polygon formed by the merging of said at least first polygon and second polygon; and updating in memory said at least one parameter of the similarity criterion, wherein the digital image divided into polygons is said new generated image and wherein the similarity criterion depends on the modified parameter.