INTERNATIONAL JOURNAL OF PROFESSIONAL ENGINEERING STUDIES Volume IV/Issue2/OCT2014 IJPRES A NOVEL APPROACH FOR POWER- CONSTRAINED CONTRAST ENHANCEMENT FOR EMISSIVE DISPLAYS BASED ON HISTOGRAM EQUALIZATION S.Priyadarsini (PG Scholar) 1 Ravi Kumar (M.tech) 2 1 Department of ECE , KV Subbareddy College Of Engineering for Women 2 Assistant Professor, Department of ECE, KV Subbareddy College Of Engineering for Women ABSTRACT  The proposed work presents a power- constrained contrast-enhancement algorithm for emissive displays based on histogram equalization (HE). To reduce the overstretching artifacts of the conventional HE log-based histogram is applied. Power-consumption model is developed for emissive displays and formulate an objective function that contain power term and histogram-equalizing term. Proposed algorithm provides contrast enhancement and power saving. Proposed algorithm is extend to enhance video sequences, as well as still images contrast and perceptual quality. Index Terms  Contrast enhancement, emissive displays, histogram equalization (HE), histogram modification (HM), image enhancement, low-power image processing. I.INTRODUCTION Due to the rapid development in the imaging technology has made easier to take and process digital photographs. We often need only low contrast image only because the lightning condition and imaging systems are not ideal. Image is enhanced by improving many factors such as sharpness, noise level, color accuracy, and contrast. High contrast is an important quality factor for provides better experience of image perception to viewer. Various contrast- enhancement techniques have been developed. For exampled, histogram equalization (HE) is widely used to enhance low- contrast images [1]. Contrast-enhancement techniques have been introduced to improve the qualities of general images, relatively little efforts has been made to adapt the enhancement, process to the characteristics of display devices. In contrast enhancement power saving is also an important issue in various multimedia devices, such as mobile phones and television but displays consume more power in such devices [2],[3]. This trends expect to continue as display size are getting larger. It is required to design a image processing algorithm, which is capable of saving power in display panels, as well as enhancing image contrast. Power-constrained contrast-enhancement (PCCE) algorithm is designed, and different characteristics of display panels should be taken into account. Modern display panels can be divided into emissive displays and non emissive displays [4]. Cathode- ray tubes, plasma display panels (PDPs), field emissive displays, and organic light - emitting diode (OLED) are emissive displays that do not required external light sources. Whereas thin-film transistor liquid crystal display (TFT-LCD) is a non emissive one. Emissive displays have several advantages over non emissive ones, including high contrast and low-power consumption. Emissive display can turn off individual pixels to obtain high contrast ratio and complete darkness. As the each pixel can be individually driven thus the power consumption by them is very less and it is proportional to they intensity level. Thus OLED and FED are considered as the promising candidates for the next generation display. OLED is consider as the most efficient emissive device in terms of power consumption [5]. OLED is mainly used for the mobile devices, its mass-production technology is being rapidly developed and large OLED panels will be adopted in wider range of device, including televisions and computer monitors [6],[7]. In [8] Choi et al increased pixel values to satisfy the brightness losses caused by reduced backlight intensity. In [2] cheng et al abbreviates both the ends of an image histogram. Then stretched pixel intensities, and Iranli et al [9] employed HE. Tsai et al [3] decomposed an image into high-and low-frequency components. Contrast enhancement and brightness compensation is applied in the subbands of the images. These techniques have been devised for TFT-LCDs only and cannot be employed for emissive displays, in which power consumption is affected by pixel values directly, rather than by backlight intensity. PCCE algorithm is proposed for the emissive displays