Apparatus and method for encoding image data
An apparatus for encoding an image data includes a sub-pixel rendering unit configured to convert a first image data of a RGB type, supplied from an outside thereof, into a second image data of a RG-BG type by performing sub-pixel rendering on the first image data, a first differential pulse code modulation (DPCM) processing unit configured to generate a first differential data including a differential value between gray scale values corresponding to green sub-pixels in the second image data, and a second DPCM processing unit configured to generate a second differential data including a differential value between a gray scale value corresponding to a red or blue sub-pixel in the second image data and an average value of gray scale values corresponding to green sub-pixels adjacent to the red or blue sub-pixel.
1. An apparatus for encoding an image data, the apparatus comprising:
a sub-pixel rendering unit configured to convert a first image data of a RGB type, supplied from an outside thereof, into a second image data of a RG-BG type by performing sub-pixel rendering on the first image data;
a first differential pulse code modulation (DPCM) processing unit configured to generate a first differential data including a differential value between gray scale values corresponding to green sub-pixels in the second image data; and
a second DPCM processing unit configured to generate a second differential data including a differential value between a gray scale value corresponding to a red or blue sub-pixel in the second image data and an average value of gray scale values corresponding to green sub-pixels adjacent to the red or blue sub-pixel.
2. The apparatus as claimed in claim 1 , wherein the second DPCM processing unit includes:
an average calculation unit configured to calculate the average value of the gray scale values corresponding to the adjacent green sub-pixels; and
a subtraction unit configured to generate the second differential data by calculating a differential value between the gray scale value corresponding to the red or blue sub-pixel and the average value.
3. The apparatus as claimed in claim 1 , further comprising an image processing unit configured to perform image processing on the first image data, in response to an image processing control signal, and output the image-processed first image data to the sub-pixel rendering unit.
4. The apparatus as claimed in claim 1 , wherein, when calculating a differential value corresponding to a leftmost sub-pixel, the second DPCM processing unit calculates, as the differential value corresponding to the leftmost sub-pixel, a difference between a gray scale value corresponding to the leftmost sub-pixel and a gray scale value corresponding to a green sub-pixel adjacent to the right side of the leftmost sub-pixel.
5. The apparatus as claimed in claim 1 , wherein the average value is an arithmetic mean value of the gray scale values corresponding to the adjacent green sub-pixels.
6. The apparatus as claimed in claim 1 , wherein the average value is calculated according to the following equation:
A
avg
=
(
G
n
-
1
γ
+
G
n
γ
2
)
1
/
γ
,
and
wherein A avg denotes the average value, G n-1 and G n denote the gray scale values corresponding to the adjacent green sub-pixels, and γ denotes a gamma constant.
7. The apparatus as claimed in claim 1 , wherein each differential value included in the second differential data is stored using three bits or less.
8. A method for encoding an image data, the method comprising:
converting a first image data of a RGB type, supplied from an outside, into a second image data of a RG-BG type by performing sub-pixel rendering on the first image data;
generating a first differential data including a differential value between gray scale values corresponding to green sub-pixels in the second image data; and
generating a second differential data including a differential value between a gray scale value corresponding to a red or blue sub-pixel in the second image data and an average value of gray scale values corresponding to green sub-pixels adjacent to the red or blue sub-pixel.
9. The method as claimed in claim 8 , wherein the converting includes:
image-processing the first image data, in response to an image processing control signal; and
converting the image-processed first image data into the second image data by performing sub-pixel rendering on the first image data.
10. The method as claimed in claim 8 , wherein the differential value corresponding to a leftmost sub-pixel among the red and blue sub-pixels is a difference between a gray scale value corresponding to the leftmost sub-pixel and a gray scale value corresponding to a green sub-pixel adjacent to the right side of the leftmost sub-pixel.
11. The method as claimed in claim 8 , wherein the average value is an arithmetic mean value of the gray scale values corresponding to the adjacent green sub-pixels.
12. The method as claimed in claim 8 , wherein the average value is calculated according to the following equation:
A
avg
=
(
G
n
-
1
γ
+
G
n
γ
2
)
1
/
γ
,
and
wherein A avg denotes the average value, G n-1 and G n denote the gray scale values corresponding to the adjacent green sub-pixels, and γ denotes a gamma constant.
13. The method as claimed in claim 8 , wherein each differential value included in the second differential data is stored using three bits or less.