Practical analysis of TIFF file size reductions achievable through compression

Abstract

• This paper presents results of a practical analysis into the effects of three main lossless TIFF compression algorithms – LZW, ZIP and Group 4 – on the storage requirements for a small set of digitized materials. In particular we are interested in understanding which algorithm achieves a greater reduction in overall storage, and whether there is any variation based on the type of file (e.g. colour depth). We compress 503 files with two software utilities – ImageMagick and LibTiff – and record the resulting file size for comparison against the original uncompressed version. Overall we find that in order to effectively (although not necessarily optimally) reduce total storage, Group 4 compression is most appropriate for 1-bit/pixel images, and ZIP compression is suited to all others. We also find that ImageMagick – which uses the LibTiff library – typically out-performs LibTiff with respect to compressed file sizes, noting that this appears to be the result of setting the “Predictor” tag.