1. A method for determining a scaled colour map of a scaled image, comprising: employing a hardware processor for: obtaining an original colour map of an original image, the original colour map having N colours; scaling an entire original image into a scaled image by resizing the entire original image with a scaling factor not equal to 1; determining a scaled colour map for the scaled image, using the original colour map and the original image only, comprising: (a) introducing respective predetermined minimum and maximum N max thresholds for a number of colours in the original colour map; (b) provided N min <N<N max : (i) selecting a sub-set of colours in the original colour map as a function of N and N max only; (ii) increasing a number of colours in the selected sub-set to form an increased sub-set of colours; (iii) forming the scaled colour map by adding the increased sub-set of colours to the original colour map.