A Fractal Image Coding Method Based on the Linear Rotation Transforms of Domain Blocks
基于相似块线性旋转变换的分形图象编码方法

Because the number of domain blocks is not sufficient in the Jacquin's fractal image coding method, the matching between domain blocks and range blocks is not very effective. To improve the matching efficiency, this paper puts forward a new fractal image coding method, which increases the number of domain blocks through linear rotation transforms and gets the optimal matching. Unlike in the ordinary methods, in order to exploit fully the self similarity in the image, this method chooses domain blocks from multiple directions in the image, then generates new sets of domain blocks through a symmetric transform and linear rotation transforms. The Isometries transforms proposed by Jacquin can be viewed as a special case of this method when the rotation direction number is fixed to 4. This method modifies the number of rotation directions, thus amends for the inadequacy of domain blocks in the Isometries transforms, and gets a better compression result. An acceleration algorithm based on a lookup table is also established for the linear rotation transforms, which effectively shortens the encoding time.