Local Contrast Normalization to Improve Preprocessing in MRI of the Brain

2021 ◽  
pp. 255-266
Author(s):  
Giuseppe Placidi ◽  
Matteo Polsinelli
2017 ◽  
Vol 2017 ◽  
pp. 1-16 ◽  
Author(s):  
Shuangshuang Chen ◽  
Huiyi Liu ◽  
Xiaoqin Zeng ◽  
Subin Qian ◽  
Jianjiang Yu ◽  
...  

Image classification aims to group images into corresponding semantic categories. Due to the difficulties of interclass similarity and intraclass variability, it is a challenging issue in computer vision. In this paper, an unsupervised feature learning approach called convolutional denoising sparse autoencoder (CDSAE) is proposed based on the theory of visual attention mechanism and deep learning methods. Firstly, saliency detection method is utilized to get training samples for unsupervised feature learning. Next, these samples are sent to the denoising sparse autoencoder (DSAE), followed by convolutional layer and local contrast normalization layer. Generally, prior in a specific task is helpful for the task solution. Therefore, a new pooling strategy—spatial pyramid pooling (SPP) fused with center-bias prior—is introduced into our approach. Experimental results on the common two image datasets (STL-10 and CIFAR-10) demonstrate that our approach is effective in image classification. They also demonstrate that none of these three components: local contrast normalization, SPP fused with center-prior, and l2 vector normalization can be excluded from our proposed approach. They jointly improve image representation and classification performance.


2020 ◽  
Vol 194 ◽  
pp. 102947
Author(s):  
Mahdi Rad ◽  
Peter M. Roth ◽  
Vincent Lepetit

Author(s):  
Tejas Rana

Various experiments or methods can be used for face recognition and detection however two of the main contain an experiment that evaluates the impact of facial landmark localization in the face recognition performance and the second experiment evaluates the impact of extracting the HOG from a regular grid and at multiple scales. We observe the question of feature sets for robust visual object recognition. The Histogram of Oriented Gradients outperform other existing methods like edge and gradient based descriptors. We observe the influence of each stage of the computation on performance, concluding that fine-scale gradients, relatively coarse spatial binning, fine orientation binning and high- quality local contrast normalization in overlapping descriptor patches are all important for good results. Comparative experiments show that though HOG is simple feature descriptor, the proposed HOG feature achieves good results with much lower computational time.


2019 ◽  
Vol 51 ◽  
pp. 144-156
Author(s):  
Yuta Hiasa ◽  
Yoshito Otake ◽  
Rie Tanaka ◽  
Shigeru Sanada ◽  
Yoshinobu Sato

2006 ◽  
Vol 25 (9) ◽  
pp. 1223-1232 ◽  
Author(s):  
A.D. Fleming ◽  
S. Philip ◽  
K.A. Goatman ◽  
J.A. Olson ◽  
P.F. Sharp

2018 ◽  
Vol 4 (10) ◽  
pp. 117
Author(s):  
Praful Gupta ◽  
Christos Bampis ◽  
Jack Glover ◽  
Nicholas Paulter ◽  
Alan Bovik

Many existing natural scene statistics-based no reference image quality assessment (NR IQA) algorithms employ univariate parametric distributions to capture the statistical inconsistencies of bandpass distorted image coefficients. Here, we propose a multivariate model of natural image coefficients expressed in the bandpass spatial domain that has the potential to capture higher order correlations that may be induced by the presence of distortions. We analyze how the parameters of the multivariate model are affected by different distortion types, and we show their ability to capture distortion-sensitive image quality information. We also demonstrate the violation of Gaussianity assumptions that occur when locally estimating the energies of distorted image coefficients. Thus, we propose a generalized Gaussian-based local contrast estimator as a way to implement non-linear local gain control, which facilitates the accurate modeling of both pristine and distorted images. We integrate the novel approach of generalized contrast normalization with multivariate modeling of bandpass image coefficients into a holistic NR IQA model, which we refer to as multivariate generalized contrast normalization (MVGCN). We demonstrate the improved performance of MVGCN on quality-relevant tasks on multiple imaging modalities, including visible light image quality prediction and task success prediction on distorted X-ray images.


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