Estimating the compression quality of an image by analysing blocking artefacts
- Authors: Roodt, Yuko
- Date: 2017
- Subjects: Image compression quality , Blocking artefacts , JPEG compression
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/247447 , uj:25692 , Citation: Roodt, Y. 2017. Estimating the compression quality of an image by analysing blocking artefacts.
- Description: Abstract: Determining the compression quality of an image is important for photo forensics and image enhancement algorithms. Unfortunately, there are a number of issues involved in determining the compression quality of an image from its metadata or quantization tables. A compression quality estimation algorithm based on visual inspection of detected compression artefacts is presented. This method detects and extracts feature samples around compression block corners. These feature samples are then pre-filtered to enhance the discontinuities produced by compression artefacts. The feature samples are then classified using a constricted Neural Network. The local quality estimations are then combined using robust statistics to estimate the maximum likelihood compression quality. This method was shown to accurately estimate the compression quality of an image without prior knowledge of the original uncompressed image.
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Super features: a probabilistic approach to feature matching and correction
- Authors: Roodt, Yuko
- Date: 2015
- Subjects: Computer vision , Image processing - Digital techniques , Pattern recognition systems , Visual analytics
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/271084 , uj:28825
- Description: D.Phil. (Electrical and Electronic Engineering) , Abstract: Please refer to full text to view abstract.
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Blind deconvolution of Gaussian blurred images containing additive white Gaussian noise
- Authors: Robinson, Philip E. , Roodt, Yuko
- Date: 2013
- Subjects: Gaussian blur , Gaussian noise , Bind deconvolution
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/16753 , uj:15807 , Robinson, P.E. & Roodt, Y. Blind deconvolution of Gaussian blurred images containing additive white Gaussian noise. IEEE International Conference on Industrial Technology (ICIT 2013), 2013, pp. 1092-1097.
- Description: Abstract: Image restoration algorithms are used to reconstruct the information that is suppressed when an observed image is subjected to blurring. These algorithms generally assume that knowledge of the nature of the distortion and noise contained in an observed image is available. When this information is not available and has to be directly estimated from the image being processed the problem becomes one of blind deconvolution. This paper makes use of a novel blur identification technique and a noise identification technique to perform blind deconvolution on single images that have been degraded by a Gaussian blur and contain additive white Gaussian noise.
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Gaussian blur identification using scale-space theory
- Authors: Robinson, Philip , Roodt, Yuko , Nel, Andre
- Date: 2012
- Subjects: Blur identification , Blur estimation , Gaussian blur , Image deblurring algorithms , Scale-space theory
- Type: Article
- Identifier: http://ujcontent.uj.ac.za8080/10210/366248 , uj:6060 , ISBN 978-0-620-54601-0 , http://hdl.handle.net/10210/10475
- Description: Image deblurring algorithms generally assume that the nature of the blurring function that degraded an image is known before an image can be deblurred. In the case of most naturally captured images the strength of the blur present in the image is not known. This paper proposes a method to identify the standard deviation of a Gaussian blur that has been applied to a single image with no a priori information about the conditions under which the image was captured. This simple method makes use of a property of the Gaussian function and the Gaussian scale space representation of an image to identify the amount of blur. This is in contrast to the majority of statistical techniques that require extensive training or complex statistical models of the blur for identification.
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Robust single image noise estimation from approximate local statistics
- Authors: Roodt, Yuko , Clarke, Wimpie , Robinson, Philip E. , Nel, André
- Date: 2012
- Subjects: Gaussian noise , Imaging sensors
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/16706 , uj:15802 , Roodt, Y., Robinson, P.E. & Nel, A. Robust single image noise estimation from approximate local statistics. Proceedings of the Twenty-Third Annual Symposium of the Pattern Recognition Association of South Africa, November 2012, pp 47-53.
- Description: Abstract: A novel method for estimating the variance and standard deviation of the additive white Gaussian noise contained in an image will be presented. Only a single image is used to estimate the noise properties. Local image outliers are discarded, this allows us to separate the additive zero mean white Gaussian noise contained in a noisy image from the original image structure. Local variance estimates can then be calculated from the extracted noise. These local variance estimates are weak and can be influenced by misclassified image information. Robust statistics are then used to fuse the weak local variance estimates to obtain a robust global noise variance estimate. This method of estimating the noise properties is computationally efficient and provides reliable estimation results in synthetic and real-world imagery. The accuracy and processing complexity of the proposed algorithm will be compared against the current state-of-the-art noise estimators.
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A new adaptive colorization filter for video decompression
- Authors: Lee, Vaughan H. , Roodt, Yuko , Clarke, William A.
- Date: 2010
- Subjects: Adaptive colorization , Graphics processing units , Video compression
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/15574 , uj:15676 , Lee, V.H., Roodt, Y. & Clarke, W.A. 2010. A new adaptive colourization filter for video decompression. Pattern Recognition Association of South Africa (PRASA), 2010.
- Description: HD content is more in demand and requires a lot of bandwidth. In this paper, a new real-time adaptive colorization filter for HD videos is presented. This approach reduces the required bandwidth by reducing non-key frames in the HD video sequence to grayscale and colourizing these frames at the decompression stage. Additionally this technique determines the frame status based on the image information.
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Text segmentation and recognition in unconstrained imagery
- Authors: Roodt, Yuko , Roos, Hans , Clarke, Willem
- Date: 2010
- Subjects: Text segmentation , Pattern recognition , Unconstrained imagery , Parallel processing (Electronic computers)
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/15395 , uj:15658 , Citation: Roodt, Y., Roos, H. & Clarke, W.A. 2010. Text segmentation and recognition in unconstrained imagery. Pattern Recognition Association of South Africa (PRASA), 2010.
- Description: Abstract: In this paper, we present a novel method for recognizing and segmenting symbols and text in complex image sequences. The algorithm is designed to take advantage of the massive computing capability of parallel processing architectures...
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Alignment invariant image comparison implemented on the GPU
- Authors: Roos, Hans , Roodt, Yuko , Clarke, Willem A.
- Date: 2008
- Subjects: Distance transform , Binary image , Graphics processing units , Parallel processing
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/15593 , uj:15681 , Roos, H., Roodt, Y. & Clarke, W.A. 2008. Alignment invariant image comparison implemented on the GPU. Pattern Recognition Association of South Africa (PRASA), 27-28 Nov. 2008.
- Description: Abstract: This paper proposes a GPU implemented algorithm to determine the differences between two binary images using Distance Transformations. These differences are invariant to slight rotation and offsets, making the technique ideal for comparisons between images that are not perfectly aligned...
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