National Repository of Grey Literature 64 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Lossy Light Field Compression
Dlabaja, Drahomír ; Milet, Tomáš (referee) ; Bařina, David (advisor)
The aim of this paper is to propose, implement and evaluate a new lossy compression method for light field images. The proposed method extends the JPEG method to four dimensions and brings new ideas which lead to better compression performance. Correlation between light field views is exploited in both dimensions by four-dimensional discrete cosine transformation. The lossy part of the encoding is performed by quantization, similarly to the JPEG method. The proposed method is implemented as a program library in a C++ language. This paper compares the proposed method to JPEG, JPEG 2000 and HEVC intra image compression methods and HEVC video compression method. The results show that the proposed method outperforms the reference methods with images with a higher amount of views. HEVC video method is better for images with fewer views or for very low bitrates.
Lossless Light Field Compression
Navrátil, Robert ; Šolony, Marek (referee) ; Bařina, David (advisor)
This thesis is focused on lossless light-field images compression, where it could be viable to extend common predictors into more dimensions. First chapter is regarding to essential theory about light-field images and 4D light-field, which is followed by description of every predictor and coder. With this is connected description of used compression pipeline. Last chapters contains description of solution and differences between every predictor result and theirs dimensional variant. At the end the results are compared with PNG. The result is that some 4D variants of implemented predictors have better compression rate than PNG.
Error Resilience Analysis for JPEG 2000
Kovalčík, Marek ; Klíma, Ondřej (referee) ; Bařina, David (advisor)
The aim of this thesis is to analyze modern image compression format of JPEG 2000. It analyzes the effect of error resilience mechanisms on image compression with different settings. The impact of using tag embedding to help repair damaged images or using compression modes to improve error resilience is examined here. Quality is evaluated by the PSNR metric that detects the similarity of compressed and reference file. Adding certain tags to the data stream or using certain compression modes should help secure the JPEG 2000 file against image reconstruction damage. To test this hipothesis, there was created a model that acidentally damage the compressed file and evaluate decompressed images. The Kakadu library, which provides efficient work with the JPEG 2000 format, is used for the work. The experimental data set consists of various photographs in uncompressed PPM format in smaller but also in higher resolutions. The result of this work is to find out which compression settings to use for which group of images to make the compression efficient and secure the best. The end of this thesis is devoted to comparison of error resilience of JPEG 2000 and CCSDS 122.0.
Analysis of JPEG 2000 Settings
Mitaš, Matěj ; Klíma, Ondřej (referee) ; Bařina, David (advisor)
This thesis analyses settings of JPEG 2000 format. The aim is to find appropriate values for each setting. Main criteria are compression performance, elapsed time and used memory. There are two libraries used that are implementing JPEG 2000 format: Kakadu and OpenJPEG. Testing was secured by framework implemented in Python. Results of this thesis enable users to use JPEG 2000 more effectively and with deeper understanding of inner workings.
Comparison of Modern Lossy Image Compression Formats
Kalabza, Marek ; Klíma, Ondřej (referee) ; Bařina, David (advisor)
This thesis compares modern compression methods of digital images on given datasets in terms of quality. First part describes the principle of lossy compression and then compression of JPEG, Lepton, JPEG 2000, JPEG XR, WebP, BPG, HEIF, H.265 intra frame, H.264 intra frame and AV1. Second part focuses on testing, comparison of results and evaluation. It also describes quality metrics (PSNR, PSNR-YUV, SSIM), deals with possible artefacts created during compression and points out the behavior of formats after data corruption. Based on testing and measurement, it was found that the best compression format from the tested lossy image formats is the AV1 format, specifically on the high resolution dataset, the scanned document dataset, and the map dataset.
Analysis of JPEG 2000 Settings
Vrtělová, Lucie ; Klíma, Ondřej (referee) ; Bařina, David (advisor)
This thesis is focused on analysis of JPEG 2000 settings. The aim of this thesis is to explore and compare each settings and different implementation. The analysis was done with two libraries, which implements JPEG 2000 - Kakadu and OpenJPEG. Data was processed by framework written in Python3. Created solution provides comprehensive view on using each settings of JPEG 2000 on specific data. Results of this thesis allow faster using of JPEG 2000 on specific data.
Comparison of Image Quality Measuring Methods
Škurla, Adam ; Klíma, Ondřej (referee) ; Bařina, David (advisor)
This thesis is aimed at image quality assessment methods and comparison of their performance regarding compression standards JPEG and JPEG 2000. First part provides information about image quality assessment basics, mentioning existing and used methods. The second part describes approach used to acquire subjective and objective rating of image quality. Further it compares obtained subjective ratings and ratings determined by objective methods. Conclusion provides an evaluation of obtained results and specification of the most suitable methods for measuring quality of images created by compression standards stated above.
New Transforms for JPEG Format
Svoboda, Stanislav ; Polok, Lukáš (referee) ; Bařina, David (advisor)
The discrete cosine transform (DCT) can be found in the heart of many image compression algorithms. Specifically, the JPEG format uses a lossy form of compression based on that transform. Since the standardization of the JPEG, many other transforms become practical in lossy data compression. This article aims to analyze the use of these transforms as the DCT replacement in the JPEG compression chain. Each transform is examined for different image datasets and subsequently compared to other transforms using the peak signal-to-noise ratio (PSNR) and SSIM. Our experiments show that an overlapping variation of the DCT, the local cosine transform (LCT), overcame the original block-wise transform at low bitrates. At high bitrates, the discrete wavelet transform employing the Cohen-Daubechies-Feauveau 9/7 wavelet offers about the same compression performance as the DCT.
GUI to FFmpeg for Building a Filter Graph
Sičkaruk, Roman ; Klíma, Ondřej (referee) ; Bařina, David (advisor)
This thesis describes creation of graphical user interface for FFmpeg filter graph conceiving tool. It includes introduction to problematics, design of an application look, structure, its implementation and comparison with similiar existing tools for another frameworks. Final tool allows user to create and edit video filter graphs, edit parameters of each filter and preview edited video.
Lossless Image Compression Using Wavelet Transform
Tumpach, Jiří ; Polok, Lukáš (referee) ; Bařina, David (advisor)
This work focuses on wavelet transform and its use in image compression particularly on a comparation between classical tensor product wavelets and new kind of second generation wavelet also known as red-black wavelet transform. Although brief comparison of EBCOT modifications, color transforms, wavelets and predictors are discussed too. A framework for an evaluation of some current methods is constructed and results across different image groups are presented. In addition, C++ library was created. Proposed lossless compression methods are better then JPEG 2000 and PNG.

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