Computer implemented method for determining a predetermined number of k representative colours from at least one digital colour image, comprising the steps of: a) obtaining at least one digital colour image having a number, p, of pixels each pixel having a colour value within an n-dimensional colour space; b) defining, irrespective of the obtained image, a predetermined number of K cluster centres which are distributed along a plurality of lines in cubic RGB colour space intersecting at an intersection point located centrally in the cubic RGB colour space, wherein K > k; c) forming clusters by, for each pixel associating its colour value with the nearest of the cluster centres; and after forming the clusters, c1) for each cluster, re-determining a cluster centre; d) reducing the number of clusters to k by deleting cluster centres and merging clusters, wherein the deleting includes: - for each cluster, determining the number of pixels associated with that cluster, and - deleting the cluster centres in case the number of associated pixels is below or equal to a predefined pruning threshold, and wherein the merging includes: - determining a distance between at least two clusters and - merging those clusters which have a distance that is smaller than a predefined merging threshold; wherein the steps c), c1), and d) are iterated; and e) from each of the resulting k clusters defining a respective representative colour. a) obtaining at least one digital colour image having a number, p, of pixels each pixel having a colour value within an n-dimensional colour space; b) defining, irrespective of the obtained image, a predetermined number of K cluster centres which are distributed along a plurality of lines in cubic RGB colour space intersecting at an intersection point located centrally in the cubic RGB colour space, wherein K > k; c) forming clusters by, for each pixel associating its colour value with the nearest of the cluster centres; and after forming the clusters, c1) for each cluster, re-determining a cluster centre; d) reducing the number of clusters to k by deleting cluster centres and merging clusters, wherein the deleting includes: - for each cluster, determining the number of pixels associated with that cluster, and - deleting the cluster centres in case the number of associated pixels is below or equal to a predefined pruning threshold, and wherein the merging includes: - determining a distance between at least two clusters and - merging those clusters which have a distance that is smaller than a predefined merging threshold; wherein the steps c), c1), and d) are iterated; and - for each cluster, determining the number of pixels associated with that cluster, and - deleting the cluster centres in case the number of associated pixels is below or equal to a predefined pruning threshold, and wherein the merging includes: - determining a distance between at least two clusters and - merging those clusters which have a distance that is smaller than a predefined merging threshold; wherein the steps c), c1), and d) are iterated; and - determining a distance between at least two clusters and - merging those clusters which have a distance that is smaller than a predefined merging threshold; e) from each of the resulting k clusters defining a respective representative colour.