1. A computer implemented method of compressing an image using one of a plurality of compression methods, said method comprising the steps of: analysing a first portion of the image to determine a compressibility score; comparing the compressibility score to a plurality of threshold values, each of the plurality of threshold values associated with a corresponding compression method from the plurality of compression methods, wherein each of the plurality of threshold values is dependent upon an amount of the analysed first portion of the image; if the compressibility score satisfies a first one of the plurality of threshold values, selecting a compression method associated with said threshold value to compress the image and if the compressibility score satisfies a second one of the plurality of threshold values, rejecting the compression method associated with said threshold value.