Underwater Acoustic Image Encoding Based on Interest Region and Correlation Coefficient

Table 1

8 kinds of isometric transformations.

Index	Transformation name	Transformed pixel
1	Identity transformation
2	Axisymmetric reflection on the vertical axis
3	Axisymmetric reflections on the horizontal
4	Symmetric reflection on the main diagonal
5	Symmetric reflection on the sub-diagonal
6	90° counterclockwise about the center
7	180° counterclockwise about the center
8	270° counterclockwise about the center