Dithering system and method for use in image processing
A dithering system includes a linear transformer, a dither data generator, an adder and a shifter. The transformer linearly transforms M bit input data using a linear function having a predetermined gradient in order to generate and output M bit transform data. The dither data generator generates and outputs M−N bit dither data. The adder adds the M bit transform data and the M−N bit dither data to generate and output M bit correction data. The shifter cuts off the bottom M−N bits of the M bit correction data in order to generate and output the N bit output data. The dithering system and associated dithering method widely disperses an error generated due to a physical limit of a data bit that can be expressed by a low gray scale system throughout the entirety of the gray scales when high gray scale image data is converted to low gray scale image data. This is done without using a lookup table which avoids using valuable chip area. In addition, by utilizing a plurality of adders and shifters rather than a multiplier and divider, the number of required logic gates is remarkably reduced as well as reducing associated power requirements.
1. A dithering system utilized in image processing, the dithering system comprising:
a linear transformer which linearly transforms received M bit input data using a linear function having a predetermined gradient to generate and output M bit transform data where M is a natural number;
a dither data generator configured to generate and outputs M−N bit dither data where N is a natural number and N<M;
an adder connected to the linear transformer and the dither data generator, the adder configured to add the M bit transform data from the linear transformer and the M−N bit dither data from the dither data generator to generate and output M bit correction data; and
a shifter connected to the adder and configured to cut-off the bottom M−N bits of the M bit correction data received from the adder to generate and output N bit output data.
2. The dithering system of claim 1 wherein the gradient of the linear function is
2
M
-
1
-
(
2
M
-
N
-
1
)
+
α
OFFSET
2
M
-
1
+
β
OFFSET
where αOFFSET is a first variable and βOFFSET is a second variable.
3. The dithering system of claim 2 wherein the linear function has a y intercept equal to the gradient of the linear function.
4. The dithering system of claim 2 wherein a numerator a of the slope of the linear function is converted to satisfy
α
=
∑
i
=
0
M
-
1
C
i
×
2
i
,
C
optimum
set
=
arg
min
∑
C
i
.
5. The dithering system of claim 4 wherein βOFFSET is 1.
6. The dithering system of claim 5 wherein the linear transformer is formed only of a plurality of adders in combination with a plurality of shifters.
7. The dithering system of claim 6 wherein the shifter is a barrel shifter.
8. The dithering system of claim 1 further comprising an over-sampling unit connected to the linear transformer is configured to over-sample the M bit input data to generate 2(M−N) identical strings of each M bit input data string and output the M−N identical strings to the linear transformer.
9. The dithering system of claim 1 wherein the linear transformer performs a fixed point calculation.
10. The dithering system of claim 1 wherein the N output data is supplied to a liquid crystal display.
11. A dithering system utilized in image processing which converts received M bit input data to N bit output data where M and N are natural numbers and N<M, the dithering system comprising:
a dither data generator configured to generate and output M−N bit dither data;
an adder connected to the dither data generator configured to add the M bit input data and the M−N bit dither data received from the dither data generator to generate and output M bit correction data;
a linear transformer connected to the adder and receiving the output M bit correction data, the linear transformer configured to linearly transform the M bit correction data using a linear function in a predetermined slope to generate and output M bit transform data; and
a shifter connected to the linear transformer and configured to cut-off the bottom M−N bits of the M bit transform data to generate and output the N bit output data.
12. The dithering system of claim 11 wherein the gradient of the linear function is
2
M
-
1
-
(
2
M
-
N
-
1
)
+
α
OFFSET
2
M
-
1
+
(
2
M
-
N
-
1
)
β
OFFSET
where αOFFSET is a first variable and βOFFSET is a second variable.
13. The dithering system of claim 12 wherein a numerator a of the gradient of the linear function is converted to satisfy
α
=
∑
i
=
0
M
-
1
C
i
×
2
i
,
C
optimum
set
=
arg
min
∑
C
i
.
14. The dithering system of claim 13 wherein βOFFSET is 2−2M−N.
15. The dithering system of claim 11 further comprising an over-sampling unit connected to the adder is configured to over-sample the M bit input data to generate 2(M−N) identical strings of each M bit input data string and output the M−N identical strings to the adder.
16. The dithering system of claim 11 wherein M is 8 and N is 6.
17. The dithering system of claim 11 wherein the dither data generator sequentially generates and outputs M−N bit dither data having different logic levels.
18. A dithering method utilized in image processing which converts M bit input data to N bit output data using dither data wherein M and N are natural numbers and N<M, the dithering method comprising:
linearly transforming the M bit input data to M bit transform data using a linear function having a predetermined gradient;
outputting the M bit transform data;
generating and outputting M−N bit dither data;
adding the M bit transform data and the M−N bit dither data to generate and output M bit correction data; and
generating and outputting the N bit output data by cutting off the bottom M−N bits of the M bit correction data.
19. The dithering method of claim 18 further comprising:
generating 2(M−N) identical strings of each M bit input data string by over-sampling the M bit input data; and
outputting the 2(M−N) identical strings to undergo the linear transformation of the M−N pieces of M bit input data to M−N pieces of M bit transform data.
20. The dithering method of claim 18 further comprising supplying the N bit output data to a liquid crystal display.
21. A dithering method utilized in image processing which converts M bit input data to N bit output data using dither data wherein M and N are natural numbers and N<M, the dithering method comprising:
generating and outputting M−N bit dither data;
generating and outputting M bit correction data by adding the M bit input data and the M−N bit dither data;
linearly transforming the M bit correction data to M bit transform data using a linear function having a predetermined gradient;
outputting the M bit transform data; and
generating and outputting the N bit output data by cutting off the bottom M−N bits of the M bit transform data.
22. The dithering method of claim 21 , further comprising:
generating 2(M−N) identical strings of each M bit input data string by over-sampling the M bit input data;
outputting the 2(M−N) identical strings of each M bit input data wherein the M bit correction data and the M−N strings of M bit correction data are generated and output by adding the over sampled 2(M−N) identical strings of each M bit input data string and a corresponding plurality of portions of M−N bit dither data.
23. The dithering method of claim 21 wherein a plurality of portions of M−N bit dither data having different logic levels is sequentially generated and outputted.