MULTI HISTOGRAM EQUALIZATION BASED CONTRAST ENHANCEMENT FOR IMAGES

Transcription

1 VOL. 10, NO. 1, JANUARY 015 ISSN ARPN Journal of Engneerng and Appled Scences Asan Research Publshng Networ (ARPN). All rghts reserved. MULTI HISTOGRAM EQUALIZATION BASED CONTRAST ENHANCEMENT FOR IMAGES P. Jagatheeswar 1, S. Suresh Kumar and T. A. Svaumar 1 1 Department of EEE, Ponjesly College of Engneerng, Nagercol, Tamlnadu, Inda Department of ECE, Sun College of Engneerng and Technology, Nagercol, Tamlnadu, Inda E-Mal: jagatheeswarss@gmal.com ABSTRACT The fundamental and mportant pre-processng stage n mage processng s the mage contrast enhancement technque. Hstogram equalzaton s an effectve contrast enhancement technque and thus n ths paper, a hstogram equalzaton based technque called Quadrant Dynamc wth Automatc Plateau Lmt Hstogram Equalzaton (QDAPLHE) s ntroduced. In ths method, a hybrd of dynamc and clpped hstogram equalzaton methods are used to ncrease the brghtness preservaton and to reduce the over enhancement. Intally, the proposed QDAPLHE algorthm passes the nput mage through a Decson based modfed medan flter (DBMMF) to remove the noses present n the mage. Then the hstogram of the fltered mage s dvded nto four sub hstograms whle mantanng second separated pont as the mean brghtness. Next, the clppng process s mplemented by calculatng automatcally the plateau lmt as the clpped level. The clpped porton of the hstogram s modfed to reduce the loss of mage ntensty value. Fnally, the clpped porton s redstrbuted unformly to the entre dynamc range and the conventonal hstogram equalzaton s executed n each sub-hstogram ndependently. Hence, the contrast enhancement s mproved and the nose amplfyng artfacts are reduced. Based on the qualtatve and the quanttatve analyss, the QDAPLHE method outperforms compared to some exstng methods n lterature. Keywords: hstogram equalzaton, mage contrast enhancement, dynamc hstogram equalzaton, clpped hstogram equalzaton, medan flter, decson based modfed medan flter. INTRODUCTION An mportant challenge n the feld of dgtal mage processng s contrast enhancement. Compared to the orgnal mage, contrast enhancement produces better mage by changng the pxel ntenstes. Of the many technques avalable for mage contrast enhancement, Hstogram equalzaton (HE) s a wdely used technque. The fundamental dea of hstogram equalzaton s to flatten the hstogram and stretch the dynamc range of the gray levels by usng the cumulatve densty functon of the mage. Nowadays, hstogram equalzaton s appled n varous applcatons such as medcal mage processng and radar mage processng [1]. In hstogram equalzaton, the brghtness of an nput mage s sgnfcantly changed and causes undesrable artfacts. Ths s not sutable for some applcatons where brghtness preservaton s necessary. To overcome the aforementoned problem, several brghtness preservng methods have been proposed []-[6]. Generally, these enhancement methods can be classfed nto two types: Parttoned hstogram equalzaton (PHE) and Dynamc parttoned hstogram equalzaton (DPHE). In these methods, the orgnal hstogram s dvded nto several sub hstograms based on the hstogram statstcal nformaton. The dfference between the PHE and DPHE s that, n the DPHE each sub hstogram s assgned to a new enhanced dynamc range nstead of usng the orgnal dynamc range. One of the popular PHE based method s Mean brghtness preservng B-Hstogram equalzaton (BBHE). BBHE segments the orgnal hstogram nto two portons by the mean of the nput hstogram. BBHE has been analyzed both expermentally and mathematcally that ths technque s capable to acheve the brghtness preservaton [1]. Later, Dualstc Sub -Image Hstogram Equalzaton (DSIHE) has been proposed. Ths algorthm separates the nput mage s hstogram nto two sub hstograms based on medan of the nput mage []. Ths technque has been clamed to outperform BBHE both n term of brghtness preservaton and also entropy (mage content) preservaton. BBHE and DSIHE methods can preserve the mean brghtness of orgnal mage n some extent. In order to provde scalable brghtness preservaton, Recursve Mean-Separate Hstogram Equalzaton (RMSHE) and Mnmum Mean Brghtness Error B-Hstogram Equalzaton (MMBEBHE) has been proposed [3]. In RMSHE algorthm, the orgnal mage s recursvely segmented nto some sub-mages based on ther mean brghtness and equalzed them separately. The better mean brghtness wll be preserved when the recursve degrees have been ncreased. If the recursve levels tend to nfnty, the output mage wll be equal to nput mage. For DPHE, there are two methods exstng n lterature: Dynamc hstogram Equalzaton (DHE) [7] and Brghtness preservng Dynamc Hstogram Equalzaton (BPDHE) [8]. The DHE parttons the hstogram of nput mage based on local mnmal and assgns a new dynamc range for each sub-hstogram. To ensure many domnatng portons, the DHE further segments the large subhstogram. To ensure many domnatng portons, the DHE further segments the large sub-hstogram through a reparttonng test. As the DHE does not consder the mean brghtness preservaton, t neglects the mean brghtness preservng and tends to ntensty saturaton artfact. 4

2 VOL. 10, NO. 1, JANUARY 015 ISSN ARPN Journal of Engneerng and Appled Scences Asan Research Publshng Networ (ARPN). All rghts reserved. To overcome the drawbacs of the DHE, brghtness preservng dynamc hstogram equalzaton (BPDHE) has been ntroduced [8]. The BPDHE uses the local maxmal as the separatng pont rather than the local mnmal. For ths reason, Ibrahm and Kong [8] clam that the local maxmals are better for mean brghtness preservaton. Fnally n BPDHE, hstogram equalzaton s mplemented after assgnng a new dynamc range for each sub hstogram. In order to mantan the mean brghtness, brghtness normalzaton s appled to ensure that the enhanced mage has smlar mean brghtness of the nput mage. Research by Praveen et al. [9] has done comparson between orgnal mage and mage enhanced by Hstogram Equalzaton and Contrast Lmted Adaptve Hstogram Equalzaton (CLAHE) for bone fracture crac detecton usng pxel value measurement. They concluded that CLAHE s better than Hstogram Equalzaton. CLAHE had been clamed also to mprove the contrast better n the applcaton of automated segmentaton of blood vessels n retnal mages when compared to Hstogram Equalzaton [10]. Kentaro Koufuta et al. [11] descrbed an approach for real tme processng of the contrast lmted adaptve hstogram equalzaton (CLAHE) usng an FPGA. In ths approach, a hstogram s generated for each pxel n an mage for remappng the pxel, and each hstogram s speculatvely dstrbuted wthout teratons by feedng bac the dstrbuton result of ts prevous pxel. But the computatonal complexty of ths approach s very hgh [9, 15]. Oo and Kong et al. [1] proposed a b-hstogram equalzaton Plateau lmt (BHEPL) as the hybrd of the BBHE and clpped hstogram equalzaton. BHEPL dvdes the hstogram of nput mage by the value of mean brghtness of the nput mage. Both the sub hstograms are clpped by each mean of hstograms of the occuped ntensty respectvely. At last, conventonal hstogram equalzaton methods are able to control the enhancement rate. In addton, these methods can avod over amplfcaton of nose n the mage. Recently, Wayalun, Pchet et al., [13] presented an enhancement algorthm for chromosome mages based on hstogram equalzaton (HE). Underwater magng s qute a challengng n the area of photography especally for low resoluton and ordnary dgtal camera. Mean values of the stretched hstogram are used to mprove the contrast of the mage [14]. An advance multband satellte colour contrast mprovement technque of a poor-contrast satellte mages s proposed based on Dscrete Cosne Transform (DCT) n [15]. The retnal mages are preprocessed usng Adaptve Hstogram Equalzaton (AHE) and the blood vessels are enhanced by applyng Top-hat and Bottom-hat transforms n [16]. Based on the nspraton of the local contrast range transform, a new general form of fast dynamc range compresson wth a local-contrast-preservaton (FDRCLCP) algorthm s developed to resolve mage enhancement problems drectly n the spatal doman [17]. Although these methods perform well for mage enhancement, the enhancement process requres hgh computatonal costs wth a large memory requrement, usually leadng to an neffcent algorthm and requrng hardware acceleraton. In ths paper, a novel method s proposed as the extenson of the BHEPL and RMSHE, called Quadrant Dynamc wth Automatc Plateau Lmt Hstogram Equalzaton (QDAPLHE). Frst, the nput mage s passed through a Decson based modfed medan flter (DBMMF) to remove the noses present n the mage. Then the proposed method dvdes the hstogram of the fltered mage nto four sub-hstograms whle mantanng second separated pont as the mean brghtness. Then the clppng process s mplemented by automatcally calculatng the plateau lmt as the clpped level. The clpped porton of the hstogram s modfed to reduce the loss of mage ntensty value. Fnally, the clpped porton s redstrbuted unformly to the entre dynamc range and the conventonal hstogram equalzaton s executed n each sub-hstogram ndependently. Hence, the contrast enhancement s mproved and the nose amplfyng artfacts are reduced. The rest of ths paper s organzed as follows. In precedng chapter, the methodology of the proposed Quadrant Dynamc wth Automatc Plateau Lmt Hstogram Equalzaton (QDAPLHE) s dscussed n detal. Then, next chapter presents the qualtatve and quanttatve analyss of exstng and proposed mage enhancement methods. The Fnal chapter serves as the concluson of ths wor. QUADRANT DYNAMIC WITH AUTOMATIC PLATEAU LIMIT HISTOGRAM EQUALIZATION (QDAPLHE) The proposed QDAPLHE method uses the fundamental dea of the RMSHE. In RMSHE the number of decomposed sub-hstograms ncreases n powers of two. Although t wll produce better brghtness preservaton, t declnes the effectveness of the hstogram equalzaton and yelds an output mage wthout a good enhancement.e., the output wll be same as the nput. Thus n ths wor, the nput hstogram s dvded nto four subhstograms. The proposed QDAPLHE conssts of four processes, namely flterng process, Hstogram parttonng process, clppng process, redstrbuton process and hstogram equalzaton. Flterng process Durng the process of samplng, transmsson and recevng of the data, t s necessary to smooth the nosy sgnals whle at the same tme preservng the edge nformaton. Dgtal mages are corrupted often by mpulse nose, due to faulty sensors n the camera, transmsson of mages through faulty channels. Two types of mpulse noses are: 1) salt and pepper nose ) random valued mpulse nose. Varous non-lnear flterng technques are formulated here. Salt and pepper nose s effectvely removed by Standard Medan Flters (SMF) by preservng the edges but flatters at hgh nose denstes [18]. The above drawbac s elmnated by an adaptve medan flter 43

3 VOL. 10, NO. 1, JANUARY 015 ISSN ARPN Journal of Engneerng and Appled Scences Asan Research Publshng Networ (ARPN). All rghts reserved. (AMF), but owng to ts ncreasng the wndow sze lead to blurrng of mages [19]. In recent years, some threshold based medan and related mpulse nose flters were proposed such as Detal preservng flter (DPF) [0], Pxel-wse MAD (PWMAD) [1] flter, Sgnal dependent ran order mean (SD-ROM) flter [], Swtched medan flters [3], [4]. The above sad flters do not have a strong decson or does not consder the local nformaton. Hence, at heavy nose levels, they fal wthout preservng the orgnal mage detals. To avod the blemsh, Decson based flter (DBA) [5] was proposed. Ths flter dentfes the processed pxel as nosy, f the pxel value s ether 0 or 55; else, t wll be consdered as not nosy. Under Hgh nosy envronment, the Decson based flter replaces the nosy pxel wth neghborhood pxel. In spte of repeated replacement of neghborhood pxel results n streas n restored mage. To avod the streas n mages, a Decson based modfed medan flter (DBMMF) [36] s proposed. Algorthm of DBMMF: The Decson based modfed medan flter (DBMMF) ntally detects mpulse and corrects t subsequently. All the pxels of an mage le between the dynamc ranges [0, 55]. If the processed pxel holds mnmum (0) or maxmum (55), pxel s consdered as nosy and processed by DBMMF else as not nosy and the pxel s unaltered. The bref llustraton of the algorthm s as follows: Step 1: Choose the wndow (-D) of sze 3x3. Pxels present n the current wndow are assumed as A xy. Step : Chec for the condton 0 < A xy < 55, f the condton s true then consder the pxel as not nosy and left unaltered. Step 3: If the processed pxel A xy holds 0 or 55.e. (A =0 or A =55) then pxel A s consdered as xy xy xy corrupted pxel. Convert -D array nto 1-D array. Sort the 1-D array whch s assumed as D xy. Step 4: Intalze two counters, forward counter (FC) and reverse counter (RC) wth 1 and 9 respectvely. When a 0 or 55 are encountered nsde the wndow FC s ncreased by 1 or RC s decremented by 1 respectvely. When the pxel s nosy, there happens to be two possble cases. Case I: If the processng pxel s nosy and the current processed wndow contans few 0 s and 55 s. So chec for 0 or 55 n sorted array D xy, smultaneously counters would propagate along the D xy array thereby elmnatng outlers retanng only the pxel that hold values other than 0 and 55. After checng all the pxels FC and RC would hold a partcular value that ndcates the number of outlers are elmnated on ether sdes. The nosy pxel s replaced by the mdpont of the sorted array. Case II: Every pxel that exsts nsde the ernel s the combnaton of 0 or 55. Even ths condton s addressed by the case I operaton, thereby mang the algorthm smple. When all the pxel elements hold 0 or 55 then the values are retaned, assumng t as texture of the mage. Step 5: Steps 1 to 4 s repeated untl all pxels of the entre mage s processed. The Quanttatve performance of the DBMMF algorthm s evaluated based on Pea sgnal to nose rato (PSNR) and Image Enhancement Factor (IEF) as n equatons (1) to (3). PSNR 10log ( L 1) / MSE (1) MSE IEF j j j 10 X (, Y (, N C Y, j X, j, j X, j Here, X (, and Y(, are the nput and output mages respectvely, C, j s the corrupted mage, N s the total number of pxels n the nput or output mages and L s the number of ntensty value. Table-1. PSNR for CT Chest mage at dfferent nose denstes Nose n % PSNR n DB () (3) SMF AMF DPF DBA DBMMF 10 % % % % % % % % %

4 VOL. 10, NO. 1, JANUARY 015 ISSN ARPN Journal of Engneerng and Appled Scences Asan Research Publshng Networ (ARPN). All rghts reserved. Table-. IEF for CT Chest mage at dfferent nose denstes. Nose n % IEF SMF AMF DPF DBA DBMMF 10 % % % % % % % % % From the Tables 1 and, t can be readly observed that the DBMMF algorthm has hgh PSNR and IEF when compared to other algorthms. The DBMMF algorthm gves excellent nose suppresson capabltes n gray scale mages corrupted by salt and pepper nose for hgh nose denstes and also fars well n preservng the global edge of the hgh detal mages and outclasses other classcal and exstng recent algorthms. Hstogram parttonng process Each mage has dfferent hstogram, whch depends on the brghtness and darness of the mage (ntensty value), and ths hstogram s parttoned to enhance the mage. The proposed QDAPLHE method dvdes the hstogram nto four sub hstograms based on mean value. The mean-based partton approach tends to segment the number of pxels equally n each sub hstogram. Hence, each separatng pont can be calculated usng the followng equatons: s.5{ I w I } (4) s s 1 h.5{ I w I } (5) h.75{ I w I } (6) 3 h Where s 1, s and s 3 are ntenstes set to 0.5, 0.50 and 0.75, respectvely, for the total number of pxels n the hstogram of the nput mage. I w and I h represent the wdth and heght of the nput mage, respectvely. Clppng process Hstogram equalzaton stretches the hgh contrast regon of the hstogram, and compresses the low contrast regon of the hstogram [7]. As a consequence, when the object of nterest n an mage occupes only a small porton of the mage, then the object wll not be successfully enhanced by hstogram equalzaton. Hstogram equalzaton method causes level saturaton effects as t extremely pushes the ntenstes towards the rght or the left sde of the hstogram. A clpped hstogram equalzaton method tends to overcome these problems by restrctng the enhancement rate. It s nown that the enhancement from hstogram equalzaton s heavly dependent on the cumulatve densty functon [c(x)]. Therefore, the enhancement rate s proportonal to the rate of c(x). The rate of c(x) s gven by the followng equaton d dx by c( x) p( x) (7) The probablty densty functon p (x) s gven h( x) p( x) (8) N where h (x) s the hstogram for ntensty value x and N s the total number of pxels n the mage. The enhancement rate s lmted by lmtng the value of p(x), or h(x) [8]. Therefore, the clpped hstogram equalzaton modfes the shape of nput hstogram by decreasng or ncreasng the value n the hstogram s bns based on a threshold lmt before the equalzaton taes place. Ths threshold lmt s also nown as the clppng lmt, or clppng threshold (T c) or the plateau level of the hstogram and based on ths threshold value, the hstograms wll be clpped. To avod the ntensty saturaton and over enhancement problem, the proposed QDAPLHE method adopts the Clpped Hstogram Equalzaton (CHE) to control the enhancement rate by defnng a plateau lmts automatcally to each sub hstogram. Here, the plateau lmt (or T c) s determned automatcally by calculatng the average occuped ntensty n each sub- hstogram. Each plateau lmt s dentfed as P s 1 s 1 m m 1 h( X ) where h ( X ) s the hstogram at the ntensty level. Clppng process s appled after fndng the plateau lmt. The clpped porton can be determned as X hx P P hx P h h c X (10) where c X h s the clpped hstogram at ntensty level. (9) 45

5 VOL. 10, NO. 1, JANUARY 015 ISSN ARPN Journal of Engneerng and Appled Scences Asan Research Publshng Networ (ARPN). All rghts reserved. Whle usng the clppng process, all the values above the plateau lmt (T c) are removed, whch may lead to loss on orgnal ntensty value of the mage. Hence, the hstogram n the clpped porton s adjusted usng the equaton (11). h mc X h h P c c X hc X P X P h X P 3 c (11) where h mc X s the modfed clpped hstogram at ntensty level. Ths type of clppng process has the effect of the contrast enhancement and reduces the nose amplfyng artfacts. Redstrbuton process Because of ths clppng process, the sub hstograms may not ensure the balance space n each subhstogram for suffcent contrast enhancement. When the sde of the sub-hstogram s narrow, contrast enhancement obtaned n narrow stretchng space s less sgnfcant and wde stretchng space ntroduces redundant contrast enhancement. Consequently, the processed mage tends to suffer from loss of mage detals and ntensty saturaton artfact. To overcome these drawbacs, the clpped porton s redstrbuted over the entre dynamc range. For ths, the proposed QDAPLHE method mantans the pont s as the brghtness preservng. The separatng ponts of s 1, s and s 3 are reassgned to a new grey level represented as t 1, t, and t 3 respectvely. t s s s (1) s s0 t s (13) s3 s t3 L 1 s s (14) s s 4 Where s 0 and s 4 are assgned to the mnmum and maxmum output ntensty value. (e., s 0 = 0 and s 4 = L-1 (55)). The new dynamc ranges are determned for all the quadrant sub-hstograms. Hstogram equalzaton The fnal step n the proposed QDAPLHE method s to equalze each new quadrant sub-hstogram ndependently. The output of hstogram equalzaton, Y(X) of ths sub-hstogram can be determned by usng the equaton (15). Y X t t t m mc 1 m 1 M h 1 (15) The total of the clpped hstogram at -th subhstogram M s gven by M m h mc m 1 X X (16) EXPERIMENTAL RESULTS AND DISCUSSIONS The performance of the proposed QDAPLHE method s tested on numerous mages. The mages le Ensten, grl, House and couple are taen from data base ( and CT abdomen mages were obtaned from Kanyaumar Government medcal college, Asarpallam, Taml Nadu, Inda wth the help of Dr. J. Ravndran. CT abdomen mage of sze 56x56 pxels s taen to evaluate the capablty of the proposed method. The proposed QDAPLHE method s qualtatvely and quanttatvely analyzed. Qualtatve analyss The qualtatve analyss nvolves performance comparson wth exstng brghtness preservng methods, namely HE, BBHE, DSIHE, MMBEBHE, RMSHE, BPDHE and BHEPL. Fgure-1 shows the output mages produced by these HE methods for the CT abdomen mage. From the expermental results, the enhancement produced by exstng methods and proposed method are shown n Fgures 1(a) to 1() for nput mages. In general, the conventonal hstogram equalzaton algorthms are prone to mssng lumnance levels due to the mappng functon calculaton and ths wll lead to cause the lac of nformaton n case of a gradaton bacground. To overcome these shortcomngs, clppng based method (QDAPLHE) s developed and the output result s shown n Fgure-1(). Based on Fgure-1(b), t s clear that the hstogram equalzaton method enhances the mages, but t also amplfes the nose level of the mages. From the Fgures 1c and 1f (BBHE, RMSHE), the drawbac of these methods s obvously seen that they preserves the mean brghtness of the mages wthout emphaszng on the mage detals sgnfcantly, that s, the problem of ntensty saturaton occurs n some regons of the mage even ths methods mprove the contrast of the mage. 46

6 VOL. 10, NO. 1, JANUARY 015 ISSN ARPN Journal of Engneerng and Appled Scences Asan Research Publshng Networ (ARPN). All rghts reserved. Absolute mean brghtness error (AMBE): The frst test whch s used as the performance measure s Absolute Mean Brghtness error (AMBE). AMBE s used to evaluate the ablty of the enhancement method to mantan the mean brghtness. (a) Orgnal Image (b) HE (c) BBHE (d) DSIHE (e) MMBEBHE (f) RMSHE (g) BPDHE (h) BHEPL () Proposed DAPLHE Fgure-1. Results for CT abdomen mage. Fgure-1() shows that the contrast of all the tested mages s enhanced successfully usng the proposed QDAPLHE method. In addton, ths method preserves the mage detals successfully. Fgures 1(g) and 1(h), shows that BPDHE and BHEPL methods produces acceptable and natural enhanced mages. Compared to these BPDHE and BHEPL methods, the proposed QDAPLHE method reduces the ntensty saturaton problem and also t can sgnfcantly mprove the performance. Quanttatve analyss To prove the robustness of the proposed methods, three nds of quanttatve comparsons tests whch are the absolute mean brghtness error, Standard devaton and Pea sgnal to nose rato have been evaluated and tabulated n Tables 3 to 5 respectvely. AMBE X m Y m (17) where, X m s the mean of the nput mage and Y m s the mean of the output mage The mnmum value of AMBE results that the mean brghtness of the nput s successfully mantaned n the output mage. Table-3 shows the AMBE measure obtaned for the sample mages. The AMBE values calculated by the exstng methods HE, BBHE, RMSHE are compared wth the AMBE value of proposed method. From the Table-3, t can be readly observed that the proposed method QDAPLHE has 13.13% less AMBE average value when compared to BHEPL, the method wth second mnmum average value. Standard devaton (Image Contrast): By measurng the standard devaton, the contrast of the mage can be studed. Standard Devaton σ s gven by L 1 l0 ( l ) p( l) (18) where Mean, L 1 l0 l p( l) and l represents the pxel value n the mage. From the Table-4, t s clear that the standard devaton value obtaned for the proposed QDAPLHE method s less compared to all the exstng methods for all the mages. Pea sgnal to nose rato (PSNR): Another quanttatve test used to measure the rchness of detals and approprateness s pea sgnal to nose rato (PSNR). Based on mean squared errors (MSE), PSNR s defned as PSNR 10 log ( L 1) / MSE (19) 10 Table-3. Absolute Mean Brghtness Error (AMPE). Images HE BBHE DSIHE MMBEBHE RMSHE (r=) BPDHE BHEPL QDAPLHE Ensten grl House couple CT abdomen Average

7 VOL. 10, NO. 1, JANUARY 015 ISSN ARPN Journal of Engneerng and Appled Scences Asan Research Publshng Networ (ARPN). All rghts reserved. Table-4. Standard Devaton (STD). Images HE BBHE DSIHE MMBEBHE RMSHE (r=) BPDHE BHEPL QDAPLHE Ensten grl House couple CT abdomen Average Table-5. Pea Sgnal to nose Rato (PSNR). Images HE BBHE DSIHE MMBEBHE RMSHE (r=) BPDHE BHEPL QDAPLHE Ensten grl House couple CT abdomen Average Where MSE j X (, Y (, N (0) X (, and Y(, are the nput and output mages respectvely, N s the total number of pxels n the nput or output mages, and L s the number of ntensty values. The PSNR values for dfferent mages are tabulated n Table-5. The PSNR values of three methods BPDHE, BHEPL and QDAPLHE are raned the frst, second and thrd hghest values respectvely. From the Table-5, t can be observed that the mages processed by proposed QDAPLHE method produces the best PSNR values, as they are wthn the range [31 db to 4 db]. From these values, t can be concluded that the proposed method performs mage contrast enhancement and produce mages wth a natural loong wth less nose amplfyng. In Overall, Both Qualtatve And The Quanttatve Tests Favor The Proposed Method QDAPLHE As The Best Among All The Exstng Methods. Thus, It Can Be Stated That The Proposed Algorthm Produces The Best Image Enhancement. CONCLUSIONS Although the hstogram equalzaton s smple and effectve algorthm for enhancement, t leads to over enhancement and ntensty saturaton problem. To overcome ths effect, dynamc hstogram equalzaton s powerful method for enhancng the low contrast mages, also n some cases t leads to nose amplfcaton and ntensty saturaton problems. To overcome the level saturaton effects occurred n hstogram equalzaton, clpped hstogram equalzaton methods are developed by restrctng the enhancement rate. Hence, a new method QDAPLHE s proposed as a hybrd of Dynamc hstogram equalzaton method and Clpped hstogram equalzaton method. The qualtatve and the quanttatve analyss are performed on the proposed method and the results are represented n the Fgure-1 and n the Tables 3 to 5. From the expermental results, both qualtatve and the quanttatve tests favor the proposed method QDAPLHE as the best among all the exstng methods. Also ths technque s more sutable for consumer electronc products where preservng the orgnal brghtness s essental. REFERENCES [1] Yeong-Taeg Km Contrast Enhancement Usng Brghtness Preservng B-Hstogram Equalzaton. IEEE Trans Consumer Electroncs. 43(1): 1-8. [] Y. Wang, Q. chen and M. M. Zhang Image Enhancement based on Equal Area Dualstc Submage Hstogram Equalzaton Method. IEEE Transactons on Consumer Electroncs. 45(1): [3] S. D. Chen and A. R. Raml Mnmum mean brghtness error b-hstogram equalzaton n contrast enhancement. IEEE Trans. Consumer Electroncs. 49(4): [4] Ta-Shng Wong, C. A. Bouman and I. Polla Image Enhancement Usng the Hypothess Selecton 48

8 VOL. 10, NO. 1, JANUARY 015 ISSN ARPN Journal of Engneerng and Appled Scences Asan Research Publshng Networ (ARPN). All rghts reserved. Flter: Theory and Applcaton to JPEG Decodng. IEEE Transactons on Image Processng. : [5] J. S. Bartune, M. Nlsson, B. Sallberg and I. Claesson Adaptve Fngerprnt Image Enhancement Wth Emphass on Preprocessng of Data. IEEE Transactons on Image Processng. : [6] Xaolng Xao and Xang Zhang An Improved Unsharp Masng Method for Borehole Image Enhancement. In proc. nd IEEE Internatonal Conference on Industral Mechatroncs and Automaton-ICIMA. pp [7] M. A. A. Wadud, M. H. Kabr, M. A. A. Dewan and O. Chae A dynamc hstogram equalzaton for mage contrast enhancement. IEEE Trans. Consumer Electroncs. 53(): [8] H. Ibrahm and N. S. P. Kong Brghtness preservng dynamc hstogram equalzaton for mage contrast enhancement. IEEE Trans. Consumer Electroncs. 53(4): [9] N. R. S. Praveen, M. Phl and M. Sath Enhancement of BoneFracture Images by Equalzaton Methods. In proc. Internatonal Conference on Computer Technology and Development. pp [10] K. Y. Pang, L. lznta, A. Fadzl and Vjanth Segmentaton of Retnal Vasculature n Colour Fundus Images. In proc. Conference on Innovaton Technologes n Intellgent Systems and Industral Applcatons (CITISIA). pp [11] Kentaro Koufuta and Tsutomu Maruyama Real-tme processng of contrast lmted adaptve hstogram equalzaton on FPGA n proc. Internatonal Conference on Feld Programmable Logc and Applcatons. pp [1] C. H. Oo, N. S. P. Kong and Ibrahm Bhstogram wth a plateau lmt for dgtal mage enhancement. IEEE Trans. Consumer Electroncs. 55(4): [13] Wayalun and Pchet. 01. Images Enhancement of G-band Chromosome usng hstogram equalzaton, OTSU thresholdng, morphologcal dlaton and flood fll technques. In proc. 8th IEEE Internatonal Conference on Computng and Networng Technology (ICCNT). pp [14] Shamsuddn. 01. Sgnfcance level of mage enhancement technques for underwater mages. In proc. IEEE Internatonal Conference on Computer and Informaton Scence (ICCIS). 1: [15] A. K. Bhandar, A. Kumar, G. K. Sngh. 01. SVD Based Poor Contrast Improvement of Blurred Multspectral Remote Sensng Satellte Images. In proc. IEEE Thrd Internatonal Conference on Computer and Communcaton Technology (ICCCT). pp [16] K. Saranya, B. Ramasubramanan and S. Kaja Mohdeen. 01. A novel approach for the detecton of new vessels n the retnal mages for screenng Dabetc Retnopathy. In proc. IEEE Internatonal Conference on Communcatons and Sgnal Processng (ICCSP). pp [17] Ch-Y Tsa. 01. A Fast Dynamc Range Compresson wth Local Contrast Preservaton Algorthm and Its Applcaton to Real-Tme Vdeo Enhancement. IEEE Transactons on multmeda. 14(4): [18] J. Astola and P. Kuosmaneen Fundamentals of non lnear Dgtal Flterng. Boca Raton, FL, CRC. [19] H. Hwang and R. A. Hadded Adaptve medan flter: New algorthms and results. IEEE transacton on mage processng. 4(4): [0] Naf Alajlan, Mohamed Kamel and Ed Jerngan Detal Preservng mpulse nose removal. Internatonal journal on Sgnal processng: mage communcaton. 19: [1] B. V. Crnojev, V. Senand and Z. Trpovs Advanced mpulse detecton based on pxel-wse MAD. IEEE sgnal Processng Letters. 11: [] E. Abreu, M. Lghtstone and S. K. Mtra An effcent approach for the removal of mpulse nose from hghly corrupted mages. IEEE transactons on mage Processng. 5: [3] P. E. Ng and K. K. Ma A swtchng medan flter wth boundary dscrmnatve nose detecton for extremely corrupted mages. IEEE Transactons on mage processng. 15(6): [4] S. Zhang and M. A. Karm. 00. A new mpulse detector for swtchng medan flters. IEEE Sgnal processng letters. 9(11): [5] K. S. Srnvasan and D. Ebenezer A new fast and effcent decson based algorthm for the removal of hgh densty mpulse nose. IEEE Sgnal processng letters. 14(3): [6] S. Esarajan, T. Veeraumar, N. Adabala, Subramanyam and C. H. Prem Chand Removal of hg h densty Salt and pepper nose through modfed decson based Unsymmetrcal trmmed 49

9 VOL. 10, NO. 1, JANUARY 015 ISSN ARPN Journal of Engneerng and Appled Scences Asan Research Publshng Networ (ARPN). All rghts reserved. medan flter. IEEE Sgnal processng letters. 18(5): [7] Nymlhagva Sengee and Heung Koo Cho Brghtness preservng weght clusterng hstogram equalzaton. IEEE Trans. Consumer Electroncs. 54(3): [8] M. Stephen, R. Pzer, Eugene Johnston, P. James, Ercsen Bonne, C. Yanasas and E. Keth Muller Contrast-lmted adaptve hstogram equalzaton: speed and effectveness. In Proc. Frst Conference on Vsualzaton n Bomedcal Computng. pp