We succeeded in improving the image quality of a color reproduction image by using random phase-free method. This method enabled the zoom of the reproduction image without lens. Conventional color computer-generated hologram was applied random phase to enlarge reproduction image regardless of hologram size. However, the random phase generated speckle noise and degraded the reproduction image. Computer-generated hologram was encoded with Frank code and Schroeder code to reduce a speckle noise at the time of reproduction. The both method need lens to expand reproduction image in optical system. In this paper, we used random phase-free method to improve the reproduction image. As the result of simulation and experiment with optical system, we succeeded in improving the image quality and enlarging the color reproduction image.

View full abstract

In this paper, we propose a background model by using an exponentially weighted updating method. We realize to reduce memory usage for construction of background model. Our background model is represented as a histogram according to pixel values. Our model uses an exponential increasing weight for updating our model. In our model, recently observed pixels have a bigger influence on the background model than older ones. Therefore, our model gradually ignores the effect of old-observed value on a background model without retaining past pixel values. We apply our method to background subtraction for comparing with conventional methods using kernel density estimation. In experiments, we confirmed that the detection accuracy of our background model is comparable to that of conventional methods.

View full abstract

Discrete Cosine Transform (DCT) is an effective image compression method based on the orthogonal transform. However, it is well known that the visual quality of encoded images using DCT is deteriorated around edge at the lower bit rate. On the other hand, Independent Component Analysis (ICA) can derive an inherent set of bases which are correspond to local features for a given input image. When ICA has been applied to image compression instead of DCT, its coding performances is inferior to the conventional DCT method. This paper presents ICA-DCT hybrid typed image coding. In our method, each signal of small region in the input image is transformed by ICA or DCT appropriately in the viewpoint of the reduction of the bit rate. In order to solve the problem that a set of ICA bases in the proposed method has the higher redundancy, the quantitative measure to extract the important ICA basis is defined as the fluctuation of bit rate by the replacement of ICA basis using a set of DCT bases. It is seen in our experimental results that the coding performance of the proposed method is improved in about 0.5 [dB] compared with the conventional DCT method for real world images.

View full abstract

This paper describes an improvement of pencil stroke map which is proposed as a pencil line drawing method. Pencil stroke map detects gradient of image and products pencil line drawing by convolution line segment with respect to each angle of gradient. However, this method has the problem that if length of line segment for convolution is unsuitable for size of graphic, resulting image loses the shape of them or degrades its quality as pencil line drawing. On this account, proposed method classifies graphics by size and change the length of line segment depending on classification result, resulting image can be obtained with improved this problem. In experiment, this paper shows effectiveness of proposed method by comparison of resulting image between proposed method and pencil stroke map.

View full abstract