톤 매핑과 컬러 영상의 흑백화

Abstract

This thesis deals with two applied research topics on digital imaging

one is a tone mapping which approximates the appearance of high dynamic range images to intermediate levels that can be represented by more limited dynamic range devices (display devices or printing devices), and the other is a color-to-grayscale conversion which converts color images to grayscale images. The tone mapping is essential to electronic image sensors of the digital imaging, and the color-to-grayscale conversion is useful in black-and-white representing devices (printing and displaying).Before giving a detailed account for the proposed methods, we summarize the digital imaging and explain its fundamental topics

optical system of digital imaging, basic terminology of digital imaging, presented algorithms.In the electronic image sensor, the high dynamic range of natural luminance has to be approximated in the limited dynamic range. This is dynamic range compression, and tone mapping is the operation that approximates the appearance of high dynamic range images to intermediate levels that can be represented by more limited dynamic range devices (display devices or printing devices). Recently, the tone mapping is applied to acquire a high quality digital image using ADCs over 14-bit with a computational unit in digital cameras. Simple representative curves for the tone mapping are linear, cumulated histogram, and logarithmic curves. This thesis presents a novel tone mapping algorithm incorporating the three simple curves by a projection operation. The proposed tone mapping takes advantage of each tone mapping curve efficiently.The acquired digital image is displayed, stored, or printed through various devices. When the image is printed on a black-and-white device, color images should be converted to black-and-white (grayscale) images. In this thesis, a novel colorto-grayscale conversion is presented, which is converting color images to grayscale images by reducing dimensions. The reducing process takes the projection operation in the imensions. The proposed method has the advantages of preserving chromatic contrasts, maintaining luminance consistency, and having a low computational cost. Furthermore, the proposed method has high resistance to artifacts such as halos that can occur when using local contents.