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Vol. 1 Issue V, December 2013 ISSN: 2321-9653
INTERNATIONAL JOURNAL FOR RESEARCH IN AP PLIED SCIENCE AN D E N G I N E E R I N G T E C H N O L O G Y (I J R A S E T)
SURVEY ON VARIOUS IMAGE CONTRAST ENHANCEMENT TECHNIQUES Jeena Baby#1, V. Karunakaran*2 #1
PG Student, Computer Science Department, Karunya University
#2
Assistant Professor, Computer Science Department, Karunya University
Abstract— In this paper a survey on various image contrast enhancement techniques has been done. Colour image enhancement plays an important role in digital image processing. Contrast enhancement is an optimization problem and is done for the images which are experiencing poor quality. Poor quality on images is due to various factors like environmental lighting conditions, defects in photographic devices etc. Therefore image contrast enhancement is important in order to improve the human acceptance rate. Most of the papers are based on histogram equalization technique and its extensions. Histogram equalization is a contrast enhancement technique based on histogram of the image. Each technique has got its own advantages as well as disadvantages. Various contrast enhancement techniques have been proposed by different authors as an extension of the traditional histogram equalization. They are power constrained contrast enhancement, dynamic range compression, colour model conversion, gamma correction and channel division methodologies. Several recent papers are being surveyed under each technique. Keywords— histogram equalization, gamma correction, contrast enhancement, local tone mapping, brightness preservation. have been proposed like histogram equalization, gamma correction, dynamic range compression etc.
I. INTRODUCTION Image enhancement is a process of improving the visual appearance of an image to make it more acceptable for the human or machine. Image enhancement is done by changing some attributes of the image. Different techniques are available for the image enhancement. Contrast enhancement is one of the image enhancement techniques. Image enhancement methods can be categorized into two type’s namely spatial domain methods and frequency domain methods. In spatial domain methods, we are directly dealing with the pixels of the image and in frequency domain methods, the image is converted to frequency domain and then the processing is done for the enhancement and finally it is converted back to original image. In order to convert it to frequency domain, Fourier transform operations are performed on the image. Contrast enhancement is done when the image quality is suffering from poor contrast due to the environmental lighting conditions or due to the defect in the photographic devices. In the case of dimmed images or dimmed videos the contrast enhancement is an essential factor that needs to be considered. Under the contrast enhancement technique several algorithms
In this paper several contrast enhancement techniques have been proposed like histogram equalization, gamma correction, frequency domain methods, channel division methods, dynamic range compression methods and colour model conversion techniques. II. HISTOGRAM EQUALIZATION Power saving is an important issue in multimedia devices. A large portion of the power is consumed by the display panels of these devices [21]. There are two types of display panels, emissive displays and non emissive displays [22].
Several contrast enhancement algorithms have been developed for non emissive displays, which needs external light sources. In [1] they have proposed a power constrained contrast enhancement algorithm for emissive displays which is based on histogram equalization. Initially they developed a histogram modification (HM) scheme for reducing large histogram values to control the contrast overstretching of the
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