Yuriy Romanyshyn

HISTOGRAM-BASED METHOD FOR NO-REFERENCE MEASUREMENT OF GENERALIZED CONTRAST OF COMPLEX IMAGES

Background. Nowadays the task of automatically measuring of image quality in real time is extremely relevant for the vast majority of practical applications. No-reference quantitative assessment of image quality is one of the most pressing and difficult problems of image processing. Generalized contrast is the most important quantitative characteristic which determines the objective quality of the image. Currently, the development of new effective methods of no-reference measuring of generalized contrast for complex image in automatic mode with the level of computing costs, which are acceptable to implement the processing in real time, is one of the most urgent tasks of image preprocessing. Objective. Development of new histogram-based method for no-reference measurement of generalized contrast of complex (multi-element) images based on the average contrast of image elements (objects and background) for different definitions of contrast kernel. Methods. Analysis of known approaches to measurement of a local contrast of the image elements, of known methods of the quantitative assessment of generalized contrast of complex images as well as of the experimental research results for a series of complex real and test images allowed revealing inherent patterns (accordance to basic requirements to the definition of contrast, the nature and the dynamic of contrast changes at the linear transformations of the brightness scale), which are manifested depending on the use of the different definitions of the contrast kernels and the metrics of generalized contrast of images. Results. No-reference contrast metrics for the histogram-based measuring of generalized contrast of complex images based on the average contrast of image elements for different definitions of contrast kernel is proposed. Conclusions. Proposed no-reference metrics based on the average contrast of image elements for proposed contrast kernels allow providing accurate quantitative assessment (measurement) of generalized contrast of the real complex images and enable to evaluate (predict) with reasonable accuracy the perceived image quality at carrying out of subjective (qualitative) expert estimates.

No-reference contrast assessment by image histogram

The problem of no-reference measurement of image contrast is considered. The method of no-reference quantitative assessments of image contrast using different contrast kernels is proposed. A comparison of the proposed and known histogram-based methods of image contrast measurement of was carried out. Examples to illustrate the effectiveness of proposed method are given.

Histogram-based method for image contrast enhancement

The problem of image contrast enhancement was considered. The histogram-based method for image contrast enhancement in automatic mode on the basis of the contrast distribution function at the boundaries of image elements (objects and background) for the different definitions of contrast kernels is proposed. A comparison of the proposed and known histogram-based methods of image contrast enhancement was carried out.

A generalized description of the weighted contrast

In this paper the problem of no-reference measurement of the contrast of image elements (objects and background) for complex multi-element images is considered. A generalized description of the weighted contrast of the image elements was proposed. New definitions for the weighted contrast of the image elements are proposed. A comparison of the proposed and known definitions of weighted contrast was carried out.

No-reference contrast metric for medical images

The problem of no-reference measurement of generalized contrast of complex medical images is considered. The histogram-based method for no-reference measuring the generalized contrast by finding the weighted mean of all possible values of the generalized contrast which correspond to all possible values of the adaptation level for current image is proposed. The proposed method of contrast measurement is intended for automatic contrast assessment of multi-element medical images with complex structure. A comparison of the proposed and known histogram-based methods of no-reference measurement of image contrast was carried out. Examples to illustrate the effectiveness of proposed method of contrast measurement are given.

Medical image contrast enhancement based on histogram

The problem of image enhancement for low-contrast medical images with complex structure was considered. The histogram-based method for automatic contrast enhancement of low-contrast images with small-size objects on the basis of the analyzing of contrast distribution at boundaries of objects and background was proposed. The proposed method is intended for automatic preprocessing of complex medical images with small-size low-contrast objects (with the details) in image. The research of the effectiveness for the proposed and the well-known histogram-based methods of automatic contrast enhancement were conducted using the known no-reference contrast metrics.

Energy model of neuron activation

On the basis of the neurophysiological strength-duration (amplitude-duration) curve of neuron activation (which relates the threshold amplitude of a rectangular current pulse of neuron activation to the pulse duration), as well as with the use of activation energy constraint (the threshold curve corresponds to the energy threshold of neuron activation by a rectangular current pulse), an energy model of neuron activation by a single current pulse has been constructed. The constructed model of activation, which determines its spectral properties, is a bandpass filter. Under the condition of minimum-phase feature of the neuron activation model, on the basis of Hilbert transform, the possibilities of phase-frequency response calculation from its amplitude-frequency response have been considered. Approximation to the amplitude-frequency response by the response of the Butterworth filter of the first order, as well as obtaining the pulse response corresponding to this approximation, give us the possibility of analyzing the efficiency of activating current pulses of various shapes, including analysis in accordance with the energy constraint.

Adaptive Enhancement of Monochrome Images with Low Contrast and Non-uniform Illumination

The problem of adaptive enhancement for complex images with low contrast and non-uniform illumination is considered. The histogram-based method of image contrast enhancement in automatic mode on the basis of the estimations of parameters of distribution of brightness values at the boundaries of objects and background for the various known definitions of contrast kernels is proposed. The research of the effectiveness of the proposed and well-known methods of image contrast enhancement is carried out using the known no-reference metrics of generalized contrast of image.

No-reference metric of generalized contrast for complex images

The problem of no-reference measurement of generalized contrast for complex multi-element images is considered. The histogram-based method for no-reference measuring the generalized contrast of multi-element images is proposed, based on the use of the average value of the summary contrast for all pairs of image elements relative to the value of the adaptation level, at which the contrast accepts a minimum value. The no-reference metric of generalized contrast is also proposed, based on the use of the value of adaptation level, at which the generalized contrast of the current image accepts a minimum value. A comparison of the proposed and known histogram-based metrics of generalized contrast was carried out.

Automatic histogram-based contrast enhancement for low-contrast images with small-sized objects

The problem of image enhancement for low-contrast images with the small-size objects is considered. The histogram-based method for contrast enhancement of low-contrast images with the small-size objects on the basis of the estimation of parameters of contrast distribution at boundaries of image elements for the various definitions of contrast kernels is proposed. The proposed method is intended for the automatic preprocessing of low-contrast images with complex structure. The researches of the effectiveness for the proposed and the well-known histogram-based methods were conducted using the known no-reference contrast metrics.