Leszek J. Chmielewski

Leszek J. Chmielewski
Warsaw University of Life Sciences - SGGW | SGGW · Institute of Information Technology

D.Sc., Eng.; Assoc. Prof.

About

107
Publications
17,811
Reads
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326
Citations
Additional affiliations
January 2010 - September 2019
Warsaw University of Life Sciences
Position
  • Head of Faculty
Description
  • Image processing in biology and medicine
January 2010 - present
Warsaw University of Life Sciences
Position
  • Image processing and other topics related to information science
May 1986 - December 2009
Institute of Fundamental Technological Research
Position
  • Professor
Description
  • Image processing in technology, biology and medicine

Publications

Publications (107)
Conference Paper
Full-text available
Color visual cryptography with truly random shares is attractive because transferring pure noise conceals the very fact that actually the information is transferred. The previously proposed method exhibits two types of errors, which lead to representing color with loss of brightness and to the presence of spikes with excessive brightness. The metho...
Article
Full-text available
The concept of black and white visual cryptography with two truly random shares, previously applied to color images, was improved by mixing the contents of the segments of each coding image, and by randomly changing a specified number of black pixels into color ones. This was done in such a way that the changes of the contents of the decoded image...
Conference Paper
Full-text available
The concept of color visual cryptography with truly random shares is proposed. The randomness was confirmed with the battery of 15 NIST randomness tests. The two shares are generated as two equal purely random sequence of R, G, B and black pixels. Coding is performed by swapping the pixels in the second share in small subregions called segments. Th...
Data
This is the supplementary material to the paper: L.J. Chmielewski, M. Nieniewski, A. Orłowski, Testing the randomness of shares in color visual cryptography, PAA, doi:10.1007/s10044-021-00999-5. Please do not cite this source independently of the paper.
Conference Paper
Full-text available
Actual randomness of the shares in the binary random visual cryptography protocol was tested with the NIST statistical test suite. Lack of randomness was noticed for a large secret image (shares 10K by 10K) in that the OverlappingTemplate test failed. The symptom of failure was much weaker for a twice smaller image and absent for a four times small...
Book
This book constitutes the refereed proceedings of the International Conference on Computer Vision and Graphics, ICCVG 2020, held in Warsaw, Poland, in September 2020. The 20 full papers were selected from 49 submissions. The contributions cover topics such as: modelling of human visual perception; computational geometry; geometrical models of objec...
Article
Full-text available
Most of the methods of classification of breast lesions in ultrasound (US) images have been tested on B-mode images from the commercial equipment. The new possibility of further analysis of this problem showed up with the availability of a public database containing original raw radio frequency (RF) signals. In particular, it appeared that the orig...
Article
Full-text available
The problem of segmenting the cross-section through the longissimus muscle in beef carcasses with computer vision methods was investigated. The available data were 111 images of cross-sections coming from 28 cows (typically four images per cow). Training data were the pixels of the muscles, marked manually. The AlexNet deep convolutional neural net...
Article
Full-text available
Textural features based upon thresholding and run length encoding have been successfully applied to the problem of classification of the quality of lacquered surfaces in furniture exhibiting the surface defect known as orange skin. The set of features for one surface patch consists of 12 real numbers. The classifier used was the one nearest neighbo...
Conference Paper
Full-text available
The concept of black and white visual cryptography with two completely random shares, recently applied to color images, was improved by mixing the contents of the segments of each coding image, or share, which correspond to one pixel in the secret coded image. The mixing was done in two ways: by permuting the 2 by 2 tiles with which the shares were...
Chapter
Full-text available
The concept of visual cryptography with two completely random shares is applied to color images. In the classic coding the shares are not correlated with the coded image, but are not totally random. We apply a completely random coding, proposed previously for the case of black and white images, to color images. This improves the security of the pro...
Chapter
Full-text available
Standard Naor-Shamir visual cryptography scheme is modified in a way that allows sampling from all possible 16 two-by-two tiles for generating shares. Such a procedure makes shares not only looking random but simply being random in the statistical sense. Of course there is a price to pay in the form of slightly deteriorated quality of the reconstru...
Conference Paper
Full-text available
A method for detection of changes in one-dimensional data based on a combination of a detector consisting of competitive filters and statistical tests is elaborated. Using synthetic data, without noise and with noise of various strengths, our method is compared with the V-Box method and the CUSUM chart. The efficiency of the algorithms is evaluated...
Conference Paper
Full-text available
A modification of the standard Naor-Shamir scheme for visual cryptography and visual secret sharing is proposed. Better statistical properties of shares are obtained at the cost of the slightly worse quality of reconstructed images. Advantages and disadvantages of such an approach are discussed.
Article
Full-text available
The aim of the research was to compare alluvial bed topography description in laboratory conditions using the “traditional”, currently applicable method with an original approach, based on LiDAR technology. LiDAR application in local scours shape investigation in based on the grounds of introducing the autonomic measuring module, which, placed abov...
Conference Paper
Full-text available
The set of prime numbers visualized as Ulam spiral was considered from the image processing perspective. Sequences of primes forming line segments were detected with the special version of the Hough transform. The polynomials which generate the numbers related to these sequences were investigated for their potential richness in prime numbers. One o...
Chapter
Full-text available
Time-dependent cross-correlation functions have been calculated between returns of the major indices of the world stock markets. One-, two-, and three-day shifts have been considered. Surprisingly high and persistent-in-time correlations have been found among some of the indices. Part of those correlations can attributed to the geographical factors...
Chapter
Full-text available
The concept of the competitive edge detector is revisited and extended. In the case of application to 1D signals it can be denoted as the detector of changes. In the detector two approximators are used working one at the ‘past’ and one at the ‘future’ side of the considered data point. The difference of their outputs makes it possible to find the c...
Chapter
Full-text available
The surfaces of furniture elements having the {\em orange skin} surface defect were investigated in the context of selecting optimum features for surface classification. Features selected from a~set of 50 features were considered. Seven feature selection methods were used. The results of these selections were aggregated and found consistently posit...
Conference Paper
Full-text available
Artificial neural networks are capable of constructing complex decision boundaries and over the recent years they have been widely used in many practical applications ranging from business to medical diagnosis and technical problems. A large number of error functions have been proposed in the literature to achieve a better predictive power. However...
Conference Paper
Full-text available
A version of the Hough transform in which the direction of the line is represented by a pair of co-prime numbers has been used to investigate the directional properties of the Ulam spiral. The method reveals the detailed information on the intensities of the lines which can be found in the square and on the numbers of primes contained in these line...
Conference Paper
Full-text available
Classification of milk duct carcinoma in the scans of diagnostic specimens is an important medical problem. Before the classification is performed, the regions of milk ducts which will be the regions of interest (ROI) should be detected. One of the approaches to such detection is to segment the image into ROIs and the remaining regions. The segment...
Article
Full-text available
The aim of the paper is to recognize and extract the milk duct in haematoxylin and eosin (HE) stained breast cancer tissues. The paper presents the modified K-means approach to segmentation of the milk duct in HE stained images. Instead of using single pixels we propose to consider the defined region of pixels in the process. Thanks to such modific...
Conference Paper
Full-text available
The concept of the competitive filter is reminded and its ability to find changes in 1D data is extended by adding the robustness feature. The use of two affine approximators, one at the left and one at the right side of the considered data point, makes it possible to detect the points in which the function and its derivative changes, by subtractin...
Conference Paper
Full-text available
In our previous papers we have investigated the directional structure and the numbers of straight line segments in the Ulam spiral. Our tests were limited to primes up to \(25\,009\,991\) due to memory limits. Now we have results for primes up to about \(10^9\) for the previously used directional resolution, and for the previous maximum number but...
Conference Paper
Full-text available
The accuracy of detecting the orange skin surface defect in lacquered furniture elements was tested. Textural features and an SVM classifier were used. Features were selected from a set of 50 features with the bottom-up feature selection strategy driven by the Fisher measure. The features selected were the Kolmogorow-Smirnow-based features, some of...
Conference Paper
Full-text available
The detector of jumps or changes in the function value and its derivative designed with the use of the concept of competing approximators is revisited. The previously defined condition for the existence of a jump in the function value is extended by introducing a statistical test of significance. This extension makes it possible to eliminate some f...
Conference Paper
Full-text available
We have applied the automatic theorem-prover Prover9 to prove first eleven theorems of Part 1 of Benedict de Spinoza’s Ethics. We have used a previous formalization of that segment developed by Blum and Malinovich. We have found Prover9 to be very efficient, providing proofs in tens of miliseconds. It appears that the only, but fundamental, limitat...
Conference Paper
Full-text available
In principle, the orange skin surface defect can be successfully detected with the use of a set of relatively simple image processing techniques. To assess the technical possibilities of classifying relatively small surfaces the Histogram of Oriented Gradients (HOG) and the Support Vector Machine were used for two sets of about 400 surface patches...
Conference Paper
Full-text available
Points that correspond to prime numbers in the Ulam square form straight line segments of various lengths. It is shown that the relation between the number of the segments and the number of primes present in a given square steadily grows together with the growing values of the prime numbers in the studied range up to 25 009 991 and is close to doub...
Conference Paper
Full-text available
The regularities present in the Ulam spiral provided an incentive for interesting observations in the number theory. Therefore, we have made the Ulam square an object of analysis from the image processing perspective. A~version of the Hough transform designed specially for detecting sequences of pixels forming segments of straight lines with the sl...
Conference Paper
Full-text available
The recently proposed quality measure is used to find the local ground approximation (LGA) from the data measured with the terrestrial laser scanning (TLS). The measure is the number of points in a thin layer located directly above the approximating surface. It can be optimized with the hill climbing algorithm. The method is robust against the data...
Conference Paper
Full-text available
An attempt was made to differentiate between surfaces of furniture elements having the orange skin defect and those free from it. As the detectors, the directional derivative of the image intensity along the dominating light direction and the modulus of the image intensity gradient were used. The detectors were tested on series of images with the s...
Chapter
Full-text available
K-means clustering algorithm has been used to classify patterns of Japanese candlesticks which accompany the approach to trend reversals in the prices of several assets registered in the Warsaw stock exchange (GPW). It has been found that the trend reversals seem to be preceded by specific combinations of candlesticks with notable frequency. Surpri...
Book
This book constitutes the refereed proceedings of the International Conference on Computer Vision and Graphic, ICCVG 2016, held in Warsaw, Poland, in September 2016. The 68 full papers presented were carefully reviewed and selected from various submissions. They show various opportunities for valuable research at the border of applied information s...
Conference Paper
Full-text available
K-means clustering algorithm has been used to classify major world stock market indices as well as most important assets in the War-saw stock exchange (GPW). In addition, to obtain information about mutual connections between indices and stocks, the Granger-causality test has been applied and the Pearson R correlation coefficients have been calcula...
Conference Paper
Full-text available
In the analysis of terrestrial laser scanning (TLS) data the digital terrain model (DTM) is one of important elements. To evaluate the DTM or to find the DTM by way of optimization it is necessary to formulate the measure of DTM quality. Three parameterized measures are proposed and tested against a comparative model for a series of TLS data. The m...
Conference Paper
Full-text available
The planar digital terrain model to be used in the analysis of forest measurements made with terrestrial LIDAR scanning is proposed for regions dominated by plains. The structure of the data suggests that the iterated version of the Hough transform is a suitable method. This makes it possible to reduce the time and memory requirements of the method...
Conference Paper
Full-text available
A hybrid pattern clustering algorithm connecting Particle Swarm Optimization with Simulated Annealing is proposed. The swarm particles are directly associated with the centroids of each cluster. They are assumed to move in the phase space associated under the influence of a potential generated by each pattern to be partitioned and interacting with...
Conference Paper
Full-text available
Defects in furniture elements were detected using data from a commercially available structured light 3D scanner. Out-of-plane deviations down to 0.15 mm were analyzed successfully. The hierarchical, iterated version of the Hough transform was used. The calculation of position of the plane could be separated from that of its direction due to the as...
Book
Evidence accumulation methods in digital image analysis (book in Polish) Accumulation in image processing The aim of the book is to present a number of accumulation methods in image analysis: two detectors and three image registration methods. The main element to which the largest part of the book is dedicated the line detector, that is, the dete...
Conference Paper
Full-text available
Pattern recognition analysis based on k-nearest neighbors classifiers is applied to the representation of the stock market dynamics with the help of the Japanese candlesticks augmented by the accompanying volume of transactions. Examples from a post-emerging Warsaw stock market are given. Conditions under which the Japanese candlesticks appear to h...
Conference Paper
Full-text available
In some imaging setups the following assumptions hold: the objects are opaque and viewed only from one point, their surface is continuous at least piecewise, and the occluding objects are small with respect to the viewed objects. In addition, in the application of our interest the images can be treated similarly to the case of the plane of light. T...
Article
Purpose To present results of patient positioning during routine radiotherapy for patients treated after mastectomy and to compare the inaccuracies in patient set-up for this group of patients and for the patients treated after breast conserving therapy with tangential fields. Methods and materials In total, the analysis comprised 56 pairs of port...
Article
Full-text available
Data structure and Hough-type algorithm suitable for finding the lines having the slope exactly specified by the ratio of small co-prime numbers is proposed. It is suitable for analysing images like the Ulam square in which the points representing prime numbers form such structures as contiguous lines and other regular sequences of points. This ana...
Data
This is a supplementary material to the paper: L.J. Chmielewski. Fuzzy histograms, weak fuzzification and accumulation of periodic quantities. Pattern Analysis and Applications, 9(2-3):189-210, October 2006. doi:10.1007/s10044-006-0037-7.
Conference Paper
Full-text available
Geometrical limitations on the voting process in the classical Hough transform resulting from that the detected objects are opaque to the applied means of measurement are considered. It is assumed that the measurements are made from one point, like in LIDAR scanning. The detected object is a circle and the two point elementary voting set forming it...
Book
Proceedings of the International Conference, ICCVG 2010, Warsaw, Poland, September 20-22, 2010, Part II
Conference Paper
Full-text available
This startup study suggests that more accurate and quicker methods of forestry terrestrial LIDAR data analysis can be developed, but new benchmark data sets with the ground truth data known are necessary for these methods to be validated. It follows from the literature review that the improvement in the methods can be attained by the use of newer H...
Article
Full-text available
Cancerous mass detection methods for mammographic images still miss some malignant cases on the one hand, and produce too many false-positive (FP) detections with respect to the number of true-positive (TP) detections on the other. An attempt has been described to improve the TP ratio per image and to decrease the number of FP errors in the hierarc...
Chapter
Full-text available
In the screening mammographic examination of large parts of populations thousands of mammograms are analysed. The Computer Aided Diagnosis methods available still tend to produce too many false positive (FP) detections with respect to the number of true positive (TP) detections, which makes it impractical to use such methods to support the human ob...
Data
This is a set of data - images used in the calculations described in the paper: L.J. Chmielewski. Fuzzy histograms, weak fuzzification and accumulation of periodic quantities. Pattern Analysis and Applications, 9(2-3):189-210, October 2006. doi:10.1007/s10044-006-0037-7
Article
Full-text available
The influence of the scale of a fuzzy membership function used to fuzzify a histogram is analysed. It is shown that for a class of fuzzifying functions it is possible to indicate the limit for fuzzification, at which the mode of the histogram equals the mean of the data accumulated in it. The fuzzification functions for which this appears are: the...
Chapter
Full-text available
The evidence accumulation method for finding objects having shape which can be neither parameterized nor tabularized is proposed. The result is a multi-scale measure of existence of the detected object, in the accumulator congruent with the image domain, supplemented with local information on additional features of the object. The method is impleme...
Book
Evidence accumulation methods in digital image analysis (book in Polish) Accumulation in image processing The aim of the book is to present a number of accumulation methods in image analysis: two detectors and three image registration methods. The main element to which the largest part of the book is dedicated the line detector, that is, the dete...
Article
To compare reproducibility of set-up for two different treatment techniques for external irradiation of the breast. In total, the analysis comprised 56 pairs of portal and simulator films for 14 consecutive patients treated following breast conserving therapy and 98 pairs of portal and simulator films for 20 consecutive patients treated after maste...
Conference Paper
Full-text available
The scale and rotation invariance properties of a recently proposed algorithm, using the fuzzy evidence accumulation principle, for finding lines (ridges) of non-parametric shapes is analysed. The proposed modifications consist in scaling the accumulated value with the inverse of the line width and further fuzzifying the accumulation process — alon...
Conference Paper
Full-text available
The recently proposed algorithm, using the evidence accumulation principle, for finding lines (ridges) having shape which can be neither parameterized nor tabularized is described in detail. This fuzzy, multi-scale algorithm stores the evidence in the accumulator congruent with the image domain. The primary application was finding blood vessels in...
Conference Paper
Full-text available
Image registration algorithms should be robust against partly erroneous and inconsistent data. The evidence accumulation mechanism known as the Hough Transform (HT) finds the solution indicated by the largest consistent subset of the data. The important case of feature-based registration under the simplified affine transformation, that is, translat...
Article
Prezentacja wyników odtwarzalności napromieniania pacjentów leczonych radykalnie, przy pomocy napromieniania wiązkami zewnętrznymi w Świętokrzyskim Centrum Onkologii w okresie jednego roku.
Article
Purpose: To study the accuracy of patients positioning treated with external beams in the Holycross Cancer Centre in Kielce. Material and methods: Displacements between digitised reference-simulator film and portal film were measured with the Port-Pro and home made programme AutoPort. Based on the data obtained for patients treated in the Holycross...
Chapter
Z "Wprowadzenia": Ciagły rozwój urzadzen akwizycji danych biomedycznych oraz komputerowych technik przetwarzania danych stwarzaja coraz wiecej mozliwosci lepszego rozumienia budowy i funkcjonowania róznych organów i tkanek, zdrowych oraz zmienionych patologicznie, zarówno w badaniach naukowych jak i klinicznych [1, 2, 3, 4]. Lekarze i naukowcy cor...
Conference Paper
Full-text available
Article
Full-text available
Methods of visual detection and measurement of certain surface defects of black ceramics – magnets and ferrite cores – are presented. Difficulties such as dark colour of ferrite and variability of appearance of defects under different light con-ditions have been overcome. The monochromatic images of the product surface, taken under a highly special...