using the fractal method. The concrete compression methods 
involve the three steps: 
Stepl Setting the size of domain blocks for 16 x 16 
pixels, the size of range blocks /? for 8 x 8 pixels. The 
range blocks aren’t overlapped each other, so the number of 
512 512 
range blocks in the image is x = 4096. The 
8 8 
domain blocks could overlap, therefore the number of them in 
the image is (512-16+1) x (512-16+1) = 247009. 
R 
Step2 To each range block ' , find the most similar domain 
block ^ and the relevant (¡=1^ 2...8, j=l, 2...8),^', °‘ , 
let the domain block ^ be closest to the range block 
through the domain block transformation, ¡ s the pixel 
value of domain block after the rotary-reflection and 
stretching transformations, 5- , O j are the factors of 
contrast and brightness which can make the domain block be 
closest to the range block. The main step is: 
A. The 16x16 pixels grey domain blocks are made into 8 x 
8 pixels grey domain blocks by averaging four pixels 
into one pixel. 
B. Choose the eight different basic rotary-reflection and 
stretching transformation methods for every 8x8 grey 
domain blocks: reflection by mid-vertical axis, reflection 
by mid-horizontal axis, reflection by first diagonal and 
second diagonal, rotation by 0°,90°, 18(7 ,270°. For 
each 8x8 pixel grey domain blocks, it could obtain 
eight grey blocks through the transformation. For the 
247009 different domain blocks, we get 247009x8 
different domain blocks through the eight basic 
transformations. 
C. For each domain blocks, supposing that the pixel value 
of domain block is d i; (i = \ 2, • • • 8: / = 1,2, • • • 8 ) 
after the eight transformations, r.(i=l, 2...8, j=l, 2...8) 
is the pixel value of range block. The S (contrast) 
could be obtained from: 
8 8 8 8 8 8 
»=1 7=1 /=i j=i m j=\ 
8 8 8 8 
64 XX<-(Z2X) 1 
¿=1 j=1 1=1 7=1 
(1) 
255