1 : (Regular Paper) 19 4, 2014 7 (JBE Vol. 19, No. 4, July 2014) http://dx.doi.org/10.5909/jbe.2014.19.4.453 ISSN 2287-9137 (Online) ISSN 1226-7953 (Print) a), b) Bi-Histogram Equalization based on Differential Compression Method for Preserving the Trend of Natural Mean Brightness Jae-Won Lee a) and Sung-Hoon Hong b). TV.. (over-enhancement), (false-contouring)..,..,.,. Abstract A typical histogram equalization contrast enhancement effect for improving the image quality is excellent. However, because it appears that excessive changes of the brightness values, The average brightness of the image is changing in units of frames of applications such as a TV video is unsuitable. In order to solve these drawbacks, a modified method of histogram equalization on various studies have been made. But the result images of existing methods sometimes shown visual degradations such as over-enhancement and false contouring. In this paper, we propose improved contrast enhancement method through bi-histogram equalization using target mean brightness based on differential compression method. The proposed method is based on the average brightness value by dividing the histogram, the histogram for each zone, according to the frequency differential of compression. And equalize the modified histogram based on target mean brightness. This allows to suppress deterioration of picture quality, and changes in the average brightness of each frame of video, while maintaining and improving the contrast. Experimental results show that the proposed method compared to the conventional method, the average brightness of each frame from a movie well maintained, and no degradation of the image quality showed a good effect to improve the contrast. Keyword : Bi-Histogram Equalizer, Histogram Compression, Contrast Enhancement, Mean Brightness Preserving, Trend of Mean Brightness
(JBE Vol. 19, No. 4, July 2014)... (histogram equalization) [1],., (false contouring) (over-enhancement).. (mean shift) TV,... (mean) 2 BBHE(Brightness preseving Bi-Histogram a) (Dept. of Electronic and Computer Engineering, Chonnam National University) b), (School of Electronic and Computer Engineering, Chonnam National Univ. & Information and Telecommunication Research Institute) Corresponding Author : (Sunghoon Hong) E-mail: hsh@jnu.ac.kr Tel: +82-62-530-1758 (2012H1B8A2025531). Manuscript received March 5, 2014 Revised June 16, 2014 Accepted July 17, 2014 Equalization) [2], (median) 2 DSIHE(Dualistic Sub-Image Histogram Equalization) [3], RMSHE (Recursive Mean-Separate Histogram Equalization) [4], RSIHE (Recursive Sub-Image Histogram Equalization) [5]. BHEPL (Bi-Histogram Equalization with a Plateau Limit) 2 [6]. BHENM(Bi- Histogram Equalization with Neighborhood Metric) 2 2040 sub-bin distriction metric [7].,.,. DHE(Dynamic Histogram Equalzation) (sub-histograms) [8].,. BPDHE(Brightness Preserving Dynamic Histogram Equalzation) [9]. BPDHE DHE,.. QDHE (Quadrants Dynamic Histogram Equalization)
1 : 4, [10]..,., (BHEDC). CLAHE QDHE.,,.... 2. 3, 4.. (BHEDC).,. 1.. CLAHE QDHE,..
(JBE Vol. 19, No. 4, July 2014),,... 1 (b) 1 (a) T. 1 (c) T (1)., T. T. ( ) 1 (d). CLAHE,.,. 1. (a) (b) (c) 1. Fig. 1. Procedure of differential compression histogram transformation (d)
1 : (a), (b) T. (c) 1/2, 1/3, 1/4,. (d). 2.. 1. BBHE, BHEPL, BHENM.,.. (a) (b) (c) 2. Fig. 2. Procedure of proposal histogram equalization method (c)
(JBE Vol. 19, No. 4, July 2014). 1..,... L/2(8bit L/2 = 128) (2). α = 1,, α, α. α 0.5..... (3). mean. (4) (normalized histogram) (5) (CDF : Cumulative Distribution Function). (6).. 3. 3..
1 : (a) original (b) BHEDC 1.0 (c) BHEDC 0.5 (d) BHEDC 0.2 (i) BBHE (j) BHEPL (k) BHENM (l) DSIHE 3. Fig. 3. Comparison of result of Bi-histogram equalization,.,,... SHE(Standard Histogram Equalization), BBHE, RMSHE, BHEPL, QDHE, BHENM, DHE, BPDHE, DSIHE (α =1), (α=0.5). ATMBE(Absolute Target Mean Brightness Error) GSD(Global Standard Deviation), AE(Average Entropy),. ATMBE AMBE (7). Meantarget
460 방송공학회논문지 제19권 제4호, 2014년 7월 (JBE Vol. 19, No. 4, July 2014) 의 평균 밝기값을 의미하게 되고 제안하는 방법은 α값에 따라 결정된 목표 평균 밝기값을 의미하게 된다. (7) 는 출력영상의 표준 편차값이다. 이는 전체적인 명 암대비 개선 정도를 나타내며 이 값이 높을수록 명암대비 개선이 잘 되었음을 의미한다. GSD (8) 가 높다는 것은 영상의 세부 정보가 잘 나타난다는 것을 의미한다. AE는 아래와 같이 정의된다. AE 는 영상의 세부 정보의 포함 정도를 나타내는 것으로 AE log 여기서 pout(xk)는 밝기값 k에 대한 명암대비 향상 결과 영상의 pdf이다. 마지막으로 제안하는 방법의 연산량을 측 정하기 위하여 평균 수행시간을 이용하여 비교 평가한다. 표 1은 각 알고리즘의 그림 4, 6, 8, 10, 12에 대한 결과를 평균한 객관적 성능 분석 결과이다. ATMBE는 BPDHE, QDHE, RMSHE에 이어 낮은 수치가 나왔다. (a) original image (b) SHE (c) BBHE (d) RMSHE (e) BHEPL (f) QDHE (g) BHENM (h) DHE (i) BPDHE (j) DSIHE (k) BHEDC(alpah = 1) (l) BHEDC(alpha = 0.5) 그림 4. White House 영상에 대한 명암대비 개선 결과 (9) Fig. 4. Contrast enhancement results for the image White House.
1 : 1. Table. 1. Result of Objective performance analysis Method ATMBE GSD AE (fps) SHE 79.29 74.90 5.16 0.032797 BBHE 26.16 71.52 5.72 0.125269 RMSHE 4.40 50.90 5.74 0.119862 BHEPL 18.91 68.83 5.12 0.123407 QDHE 6.41 59.85 5.84 0.946514 BHENM 19.24 69.94 6.50 0.946889 DHE 13.85 49.51 5.66 0.161638 BPDHE 0 31.83 5.46 0.157311 DSIHE 37.50 78.30 5.73 0.125029 BHEDC(1.0) 8.48 50.78 5.82 0.135194 BHEDC(0.5) 7.42 52.27 5.81 0.135194. GSD. AE local BHENM. AE, local enhancement, BHENM local enhancement... (a) original image (b) SHE (c) BBHE (d) RMSHE (e) BHEPL (f) QDHE (g) BHENM (h) DHE (i) BPDHE (j) DSIHE (k) BHEDC(alpah = 1) (l) BHEDC(alpha = 0.5) 5. White House Fig. 5. Histogram of Contrast enhancement results for the image White House.
462 방송공학회논문지 제19권 제4호, 2014년 7월 (JBE Vol. 19, No. 4, July 2014) (a) original image (b) SHE (c) BBHE (d) RMSHE (e) BHEPL (f) QDHE (g) BHENM (h) DHE (i) BPDHE (j) DSIHE (k) BHEDC(alpah = 1) (l) BHEDC(alpha = 0.5) 그림 6. Korean Actress 영상에 대한 명암대비 개선 결과 Fig. 6. Contrast enhancement results for the image Korean Actress. (a) original image (b) SHE (c) BBHE (d) RMSHE (e) BHEPL (f) QDHE (g) BHENM (h) DHE (i) BPDHE (j) DSIHE (k) BHEDC(alpah = 1) (l) BHEDC(alpha = 0.5) 그림 7. Korean Actress 영상에 대한 명암대비 개선 결과의 히스토그램 Fig. 7. Histogram of Contrast enhancement results for the image Korean Actress.
이재원 외 인 자연스러운 영상의 평균 밝기 유지를 위한 차별적 압축 방법 기반의 분할 히스토그램 평활화 1 : (a) original image (b) SHE (c) BBHE (d) RMSHE (e) BHEPL (f) QDHE (g) BHENM (h) DHE (i) BPDHE (j) DSIHE (k) BHEDC(alpah = 1) (l) BHEDC(alpha = 0.5) 그림 8. School 영상에 대한 명암대비 개선 결과 Fig. 8. Contrast enhancement results for the image School (a) original image (b) SHE (c) BBHE (d) RMSHE (e) BHEPL (f) QDHE (g) BHENM (h) DHE (i) BPDHE (j) DSIHE (k) BHEDC(alpah = 1) (l) BHEDC(alpha = 0.5) 그림 9. School 영상에 대한 명암대비 개선 결과의 히스토그램 Fig. 9. Histogram of Contrast enhancement results for the image School 463
464 방송공학회논문지 제19권 제4호, 2014년 7월 (JBE Vol. 19, No. 4, July 2014) (a) original image (b) SHE (c) BBHE (d) RMSHE (e) BHEPL (f) QDHE (g) BHENM (h) DHE (i) BPDHE (j) DSIHE (k) BHEDC(alpah = 1) (l) BHEDC(alpha = 0.5) 그림 10. Apartment 영상에 대한 명암대비 개선 결과 Fig. 10. Contrast enhancement results for the image Apartment (a) original image (b) SHE (c) BBHE (d) RMSHE (e) BHEPL (f) QDHE (g) BHENM (h) DHE (i) BPDHE (j) DSIHE (k) BHEDC(alpah = 1) (l) BHEDC(alpha = 0.5) 그림 11. Apartment 영상에 대한 명암대비 개선 결과의 히스토그램 Fig. 11. Histogram of Contrast enhancement results for the image Apartment
1 : 4 SHE. BBHE, RMSHE, BHEPL. QDHE, DHE, BPDHE,. BHENM. DSIHE SHE.. 6 SHE. BBHE, RMSHE, BHEPL, QDHE, BHENM. DHE BPDHE. DSIHE SHE.. 8 SHE, BBHE, RMSHE, BHEPL. QDHE, BHENM, DHE, BPDHE, DSIHE, QDHE, BHENM.. 10 SHE. BBHE, BHEPL, BHENM. RMSHE, QDHE, DHE, BPDHE,.. 12. TMD ( ) Fig. 12. Comparion for result of TMD(in movie minority report )
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이재원 외 인 자연스러운 영상의 평균 밝기 유지를 위한 차별적 압축 방법 기반의 분할 히스토그램 평활화 1 : 저자소개 이재원 년 3월 ~ 2009년 2월 : 전남대학교 전자컴퓨터공학부 학사 년 3월 ~ 2012년 2월 : 전남대학교 전자컴퓨터공학과 석사 년 3월 ~ 현재 : 전남대학교 전자컴퓨터공학과 박사과정 주관심분야 : 영상처리, 컴퓨터 비전, 멀티미디어시스템 - 2004-2009 - 2012 - 홍성훈 - 년 2월 : 영남대학교 전자공학과 공학사 년 2월 : 한국과학기술원 전기및전자공학과 공학석사 년 2월 : 한국과학기술원 전기및전자공학과 공학박사 년 ~ 2000년 7월 : LG전자 DTV 연구소 책임연구원 년 ~ 현재 : 전남대학교 전자컴퓨터공학부 교수 주관심분야 : 의료영상처리, 영상부호화, 멀티미디어시스템 1988 1991 1999 1991 2007 467