# Full text: Mapping without the sun

```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
```

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