Histogram equalization

About: Histogram equalization is a research topic. Over the lifetime, 5755 publications have been published within this topic receiving 89313 citations.

Binary quantification of an image having multiple levels of greys

Abstract: Method for transforming a video type image having multiple levels of greys into a binary image, method wherein each pixel is either white or black. With each pixel of the initial image there is associated a partial image centered on said pixel and comprising a plurality of pixels in at least one dimension. If the histogram of the grey levels of said partial image is considered as bimodal (D>E), a threshold (S) median with respect to said histogram is selected. If the histogram is considered as monomodal (D

Improved binarization algorithm for document image by histogram and edge detection

Abstract: A binarization method is presented to counter the stroke connectivity problems of characters arising from mid-level-quality binary image scanning systems. In the output of a binary image scanning system, separate strokes may look connected if the point size is small and the character strokes are complex while strokes may lose connectivity if they are generated at low intensity. Also, erroneous recognition may result if a blemished document surface distorts the image. To counter these problems and to further enhance the quality of character recognition, the authors have developed an integrated binarization scheme, exploiting synergistic use of an adaptive thresholding technique and variable histogram equalization. This algorithm is composed of two components. The first removes background noise via gray level histogram equalization while the second enhances the gray level of characters over and above the surrounding background via an edge image composition technique.

Color retinal image enhancement using luminosity and quantile based contrast enhancement

Abstract: Retinal imaging is used to diagnose common eye diseases. But retinal images that suffer from image blurring, uneven illumination and low contrast become useless for further diagnosis by automated systems. In this work, we have proposed a new method for overall contrast enhancement of the color retinal images. Initially, a gain matrix of luminance values which is obtained by adaptive gamma correction method is used to enhance all three color channels of the images. After that quantile-based histogram equalization is used to enhance overall visibility of the images. Enhancement results of the proposed method are compared with several other existing methods. Performance of the proposed method is evaluated on all images of publicly available Messidor database. Based on the assessment measure we have shown that the proposed method is able to enhance the contrast of given color retinal image without changing its structural information. The proposed technique is appeared to accomplish superior image enhancement with sufficient contrast enhancement, these enhancement results are better than other related techniques. This technique for color retinal image enhancement might be utilized to help ophthalmologists in the more productive screening of retinal ailments, what’s more, being developed of enhanced robotized image examination for clinical finding.

Dynamic histogram warping of image histograms for constant image brightness, histogram matching and histogram specification

Abstract: Dynamic histogram warping is performed on histograms extracted from an image pair of a scene. The warped histograms are remapped to the image pair and the resulting remapped image pair is subsequently subjected to image processing.

Dynamic histogram equalization for high dynamic range images

Abstract: Dynamic range equalization by histogram modification. A histogram is analyzed to determine locations of peaks. A mapping function is formed which relates to the locations of the peaks in a histogram. That mapping function may have areas of highest slope near the peaks. The mapping function is used to form a compressed histogram, which has the required number of levels to display on a display device.