A new progressive file format for lossy and lossless image compression
ETH Zurich, Institute of Theoretical Computer Science
ETH Zentrum, 8092 Zurich, Switzerland
We present a new image file format, called Progressive Graphics File (PGF), which is based on a discrete wavelet transform with progressive coding features. We show all steps of a transform based coder in detail and discuss some important aspects of our careful implementation. PGF can be used for lossless and lossy compression. It performs best for natural images and aerial ortho-photos. For these types of images it shows in its lossy compression mode a better compression efficiency than JPEG. This efficiency gain is almost for free, because the encoding and decoding times are only marginally longer. We also compare PGF with JPEG 2000 and show that JPEG 2000 is about ten times slower than PGF. In its lossless compression mode PGF has a slightly worse compression efficiency than JPEG 2000, but a clearly better compression efficiency than JPEG-LS and PNG. If both, compression efficiency and runtime, is important, then PGF is the best of the tested algorithms for compression of natural images and aerial photos.
Keywords: still image file format, lossy/lossless image compression, progressive coding, discrete wavelet transform.