Interactive Contrast Enhancement by Histogram Warping

Abstract

Abstract:We present an interactive contrast enhancement technique for the global histogram modification of images. Through direct manipulation, the user adjusts contrast by clicking on the image. Contrast around different key tones can be adjusted simultaneously and independently without altering their luminance. Histogram warping by monotonic splines performs the gray level mapping. User interfaces for contrast correction find application in digital photography, remote sensing, medical imaging, and scientific visualization.

Interactive image enhancement by fuzzy relaxation

“…From the IIE perspective, it is easily proved that the transformation function (2) used in Li & Yang s algorithm meets the requirements of a transformation function for IIE as addressed in [5]. In the improved Li & Yang s algorithm, which is called FuzzIIE Method 1, parameters a, b, and c (two of them are free) provide flexible ways of adjusting pixel intensities at different points for the users, and the completion of the iteration of image enhancement is based on the user s evaluation on the enhanced image.…”

“…This will reduce the fuzziness of the fuzzy set X f iteratively, leading to the expected image enhancement effect in image spatial domain. From the IIE perspective, the three free parameters a, b and c provide flexible ways of adjusting the pixel intensities at different points for the users, and the completion of the iteration of image enhancement replies on the user s evaluation on the enhanced image, and the above transformation T (·) in (27) meets the requirements of a transformation function for the IIE as addressed in [5].…”

“…Canas described an electronic hardware system capable of applying some nonlinear contrast stretches to the enhancement of video image in real time, rendering it useful as an interactive tool for the analysis and modification of image contrast on a statistical basis [4] . In order to provide an interactive contrast enhancement for global histogram modification of images, Grundland and Dodgson applied a piecewise rational quadratic interpolating spline to histogram warping [5] , and addressed the requirements of a transformation function T (·) used for IIE: the necessary degrees of freedom exist within T (·) with its parameters chosen by the user to express simultaneous and independent contrast enhancement at different points, where T (·) is continuously differentiable and T (·) ≥ 0 preserving the natural order of gray levels. Many existing transformations for contrast enhancement fail to meet these requirements [5] .…”

“…In order to provide an interactive contrast enhancement for global histogram modification of images, Grundland and Dodgson applied a piecewise rational quadratic interpolating spline to histogram warping [5] , and addressed the requirements of a transformation function T (·) used for IIE: the necessary degrees of freedom exist within T (·) with its parameters chosen by the user to express simultaneous and independent contrast enhancement at different points, where T (·) is continuously differentiable and T (·) ≥ 0 preserving the natural order of gray levels. Many existing transformations for contrast enhancement fail to meet these requirements [5] . Koren suggested an interactive contrast enhancement method by applying a piecewise linear enhancement function to discrete steerable dyadic wavelet transform coefficients [6] .…”

Color histogram specification by histogram warping

“…Our previous work 2,3 introduced histogram warping as a technique for interactive and automatic contrast enhancement of graylevel images. This paper expands our histogram warping framework to handle histogram specification for color The colors of the original images (top) are exchanged (bottom).…”