Lossless transform with functionality of thumbnail previewing

This report proposes a new functionality of lossless coding of image signals. The proposed method provides `thumbnail previewing´ of the original image from a part of the bit-stream without expanding all the compressed data. It also avoids degradation of resolution in pixel density of the thumbnail image. It is composed of a new lossless color transform and an existing lossless wavelet transform. We add a free parameter to the color transform and utilize it to control a scaling parameter of the luminance component. As a result, it became possible to preview the `thumb-nail´ luminance image from a part of the bit-stream. Due to the free parameter, quality and data volume of the `thumbnail´ can be controlled according to a users´ request. Unlike the existing two layer lossless / lossy coding, the proposed method achieves good performance in lossless coding of the original image signal.