Interested In Image Compression And Visible Watermark Technology

With rapid development of multimedia technology, the amount of image information became larger and larger, so it needs large storage capacity and a wide-band transportation channel. Image compression is achievable because of the redundant information between the adjacent pixels in an image, now it has become a hotspot. In order to satisfy all kinds of application requirement in different environment, the standard of image compression system has been improved, it not only requires a higher performance on compression, but also needs other new functions.At present, in the aspect of image compression, embedded coding algorithm based on wavelet transform is the key technology, and increasingly importance has been attached to it. In order to improve the quality and safty of ROI after image coding and decoding process, some research on image segmentation has been done, ROI extraction, such as color image compression, ROI coding and visual watermark technology, the achievements can be concluded as follows:⑴By studying the energy distribution of the color channels in the transformed color space, and the quantitative method in the traditional embeded coding, a new quantitative method for color image compression was designed, which is based on the distributing of wavelet coefficients. Combined with the keystone of SPIHT (set partitioning in hierarchical trees algorithm), the wavelet coefficients in every color channel are quantized and coded in unity. In comparison with the original quantitative scheme, the new scheme gives better image compression performance, especially in the lower bit rate, the reconstructed image after impression has higher quality.⑵Combined with the significant characteristic of human eyes and morphological watershed algorithm, this paper designed a new segmentation region-of-interest extraction algorithm used for the color image. After the segmentation process, the image retained a very fine edge of the targets, over-segmentation caused by watershed algorithm has been greatly improved, and ROI can be exactly extracted from simple background.⑶The ROI extraction method can be applied in ROI coding, in large compression rate, the experiment result shows that the quality of ROI in reconstructed image is higher than BG (background).⑷An adaptive visual watermark technical in ROI was designed, which can better protect the copyright of the image. The embedding depth is fixed by every pixel's texture feature of host image. In wavelet domain, the visual watermark is embedded into the region of interest in the image adatively, and this step can be set during the image coding. Experimental results have shown that watermarked image meet the requirements of visible watermark quite well, watermark is translucently showing in the image and ROI does receive better protection, what's more, it realizes the watermark timely, safty and no effect on compression rate.Based on the above studies, visual watermark adaptive embedded in the objects of the host image, which is realized synchronously with compression. It not only improves the performance of color image compression, but also better protects the image's copyright.