Wavelet based scalable image compression

In this paper, we present scalable image compression algorithms based oh wavelet transform. Recently, the International Standard Organization (ISO) has proposed the JPEG standard for still image compression. JPEG standard not only provides the basic feature of compression (baseline algorithm) but also provides the framework of reconstructing images in different picture qualities and sizes. These features are referred to as SNR and spatial scalability, respectively. Spatial scalability can be implemented using the hierarchical mode in the JPEG standard. However, the standard does not specify the downsampling filters to be used for obtaining the progressively lower size images. A straightforward implementation would employ mean downsampling filters. However, this filter does not perform very well in extracting the features from the full size image resulting in poor quality images and a lower compression ratio. We present a wavelet transform based technique for achieving spatial scalability (within the framework of hierarchical mode). Our simulation results confirm the substantial performance improvement and superior subjective quality images using the proposed technique. Most importantly, the wavelet based technique does not require any modifications to existing JPEG decoders.