• 한국가시화정보학회:학술대회논문집
• /
• 한국가시화정보학회 2001년도 Proceedings of 2001 Korea-Japan Joint Seminar on Particle Image Velocimetry
• /
• pp.14-22
• /
• 2001

The frequency responses on the sub-pixel evaluation technique were investigated using the Monte-calro Simulation technique. The frequency response by the FFT based cross-correlation gives very good results, however, the gain loss does exist for the small displacement, (less than 0.5 pixel). While, the no gain loss is observed in the Direct Cross-correlation, however, the sub-pixel accuracy was limited to be about 0.1 pixel, i.e., it could not detect the small displacement. To detect the higher accurate sub-pixel displacement, the gradient based technique is the best. For the small interrogation area (e.g., 4x4), only the gradient technique can detect the small displacement correctly.

• 한국통신학회논문지
• /
• 제25권10B호
• /
• pp.1813-1820
• /
• 2000

In this paper we proposed an efficient multiresolution motion estimation(MRME) algorithm using half-pixel accuracy motion estimation (HPAME) and characteristics of motion vectors in the baseband. Conventional MRME method needs exact motion vectors in the baseband because those are used as initial motion vectors in higher frequency subbands. Therefore the proposed method uses HPAME to estimate the motion vectors exactly in the baseband. Based on the characteristics of these motion vectors the motion vectors in the higher frequency subbands are selectively estimatied. That is motion vectors in the higher frequency subbands are estimated only for the blocks which have the half-pixel accuracy motion vectors in the baseband. In the proposed method by using HPAME in the baseband and selective motion estimation in the higher frequency subbands we can obtain reconstructed image with the similar quality with the conventional method though we reduce the computational complexity and the bit rate considerably.

• 한국농업기계학회:학술대회논문집
• /
• 한국농업기계학회 2017년도 춘계공동학술대회
• /
• pp.157-157
• /
• 2017

To minimize the damage by wild birds and acquire the benefits such as protection against weeds and maintenance of water content in soil, the mulching black color vinyl after seeding should be carried out. Non-contact and non-destructive methods that can continuously determine the locations are necessary. In this study, a crop position detection method was studied that uses infrared thermal image sensor to determine the cotyledon position under vinyl mulch. The moving system for acquiring image arrays has been developed for continuously detecting crop locations under plastic mulching on the field. A sliding mechanical device was developed to move the sensor, which were arranged in the form of a linear array, perpendicular to the array using a micro-controller integrated with a stepping motor. The experiments were conducted while moving 4.00 cm/s speed of the IR sensor by the rotational speed of the stepping motor based on a digital pulse width modulation signal from the micro-controller. The acquired images were calibrated with the spatial image correlation. The collected data were processed using moving averaging on interpolation to determine the frame where the variance was the smallest in resolution units of 1.02 cm. Non-linear integral interpolation was one of method for analyzing the frequency using the normalization image and then arbitrarily increasing the limited data value of $16{\times}4pixels$ in one frame. It was a method to relatively reduce the size of overlapping pixels by arbitrarily increasing the limited data value. The splitted frames into 0.1 units instead of 1 pixel can propose more than 10 times more accurate and original method than the existing correction method. The non-integral calibration method was conducted by applying the subdivision method to the pixels to find the optimal correction resolution based on the first reversed frequency. In order to find a correct resolution, the expected location of the first crop was indicated on near pixel 4 in the inversion frequency. For the most optimized resolution, the pixel was divided by 0.4 pixel instead of one pixel to find out where the lowest frequency exists.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제7권10호
• /
• pp.2514-2526
• /
• 2013

This paper presents a detection method for least significant bit matching revisited (LSBMR) steganography. Previous research shows that the adjacent pixels of natural images are highly correlated and the value 0 appears most frequently in pixel difference. Considering that the message embedding process of LSBMR steganography has a weighted-smoothing effect on the distribution of pixel difference, the frequency of the occurrence of value 0 in pixel difference changes most significantly whereas other values approximately remain unchanged during message embedding. By analyzing the effect of LSBMR steganography on pixel difference distribution, an equation is deduced to estimate the frequency of difference value 0 using the frequencies of difference values 1 and 2. The sum of the ratio of the estimated value to the actual value as well as the ratio of the frequency of difference value 1 to difference value 0 is used as the steganalytic detector. Experimental results show that the proposed method can effectively detect LSBMR steganography and can outperform previous proposed methods.

• 대한원격탐사학회:학술대회논문집
• /
• 대한원격탐사학회 2005년도 Proceedings of ISRS 2005
• /
• pp.604-607
• /
• 2005

All CCD pixels do not react uniformly even if the light of same radiance enters into the camera. This comes from the different camera optical characteristics, the read-out characteristics, the pixel own characteristics and so on. Usually, the image data of satellite camera can be corrected by the various image-processing methods in the ground. However, sometimes, the in-orbit correction is needed to get the higher quality image. Especially high frequency pixel correction in the middle of in-orbit mission is needed because the in-orbit data compression with the high frequency loss is essential to transmit many data in real time due to the limited RF bandwidth. In this case, this high frequency correction can prevent have to have any unnecessary high frequency loss. This in-orbit correction can be done by the specific correction table, which consists of the gain and the offset correction value for each pixel. So, it is very important to get more accurate correction table for good correction results. This paper shows the new algorithm to get accurate pixel correction table. This algorithm shall be verified theoretically and also verified with the various simulation and the test results.

• Current Optics and Photonics
• /
• 제5권4호
• /
• pp.409-420
• /
• 2021

We propose a method to synthesize a color non-hogel-based computer-generated-hologram (CGH) from light field data of a three-dimensional scene with a hologram pixel pitch shared for all color channels. The non-hogel-based CGH technique generates a continuous wavefront with arbitrary carrier wave from given light field data by interpreting the ray angle in the light field to the spatial frequency of the plane wavefront. The relation between ray angle and spatial frequency is, however, dependent on the wavelength, which leads to different spatial frequency sampling grid in the light field data, resulting in color aberrations in the hologram reconstruction. The proposed method sets a hologram pixel pitch common to all color channels such that the smallest blue diffraction angle covers the field of view of the light field. Then a spatial frequency sampling grid common to all color channels is established by interpolating the light field with the spatial frequency range of the blue wavelength and the sampling interval of the red wavelength. The common hologram pixel pitch and light field spatial frequency sampling grid ensure the synthesis of a color hologram without any color aberrations in the hologram reconstructions, or any loss of information contained in the light field. The proposed method is successfully verified using color light field data of various test or natural 3D scenes.

• 한국정보통신학회:학술대회논문집
• /
• 한국정보통신학회 2013년도 춘계학술대회
• /
• pp.364-367
• /
• 2013

본 논문은 모폴로지 연산을 이용하여 얼굴의 잡티를 제거하는 기법을 제안한다. 먼저, 입력받은 RGB 3채널 영상에서 각 채널의 픽셀 값을 이용하여 피부 영역을 검출한다. 피부 영역의 R, G, B 각 채널 영상에 대한 히스토그램을 만들어 각 채널 당 빈도수가 많은 픽셀 값 3개를 저장한다. 그 후, 피부 영역에 블랙햇 연산을 하여 잡티를 찾아낸다. 잡티로 검출된 픽셀은 자신의 픽셀 값과 8방향 이웃 픽셀 값, 앞에서 선택된 픽셀 3개의 평균으로 그 값을 변경한다. 그리고 잡티 부분의 픽셀에 중간값 필터를 이용하여 블러링을 한다. 잡티가 있는 얼굴 사진을 테스트 영상으로 실험한 결과 제안된 시스템은 얼굴의 잡티를 제거하여 얼굴 피부를 보정하는 방법은 단순히 영상을 밝게 하여 얼굴 피부를 보정하는 방법보다 효율적이다.

• 한국멀티미디어학회논문지
• /
• 제16권4호
• /
• pp.411-417
• /
• 2013

In this paper, we proposed a fast detection method of copy-move forgery image based on low frequency coefficients of the DCT coefficients. We proposed a new matching criterion of copy-moved forgery image detection (MCD) using discrete cosine transform. For each $8{\times}8$ pixel block, the DCT transform is calculated. Our algorithm uses low frequency four (DC, 3 AC coefficient) and six coefficients (DC, 5 AC coefficients) of DCT per $8{\times}8$ pixel block. Our algorithm worked block matching for DCT coefficients of the $8{\times}8$ pixel block is slid by one pixel along the image from the upper left corner to the lower right corner. Our algorithm can reduce computational complexity more than conventional copy moved forgery detection algorithms.

• 대한전자공학회논문지SP
• /
• 제41권5호
• /
• pp.135-141
• /
• 2004

영상 보간은 기존에 존재하는 화소의 정보로 빈 화소를 계산하여 영상을 확대하는 방법이다. 자연 영상은 다양한 공간 주파수 성분을 포함하기 때문에 하나의 영상 보간 방법으로 다양한 주파수 성분에 대한 보간을 모두 수행하기에는 어려운 점이있다. 본 논문에서는 공간 주파수 특성을 가지는 다중 신경회로망 구조를 이용하여 영상을 보간하는 방법은 제안한다. 입력 영상은 국부 분산에 의해 공간 주파수에 따라 분리되어 공간 주파수 대역 별로 설정된 신경회로망을 통하여 보간 된다. 제안 방법은 deinterlacing에서의 적용성 때문에 관심이 커지고 있는 2배의 영상 보간에 적용되었다. 모의 실험에서 제안 방법은 기존의 알고리즘들뿐 아니라 단일 신경 회로망을 사용하는 방법보다 개선된 PSNR 성능을 보여주었다.

• 한국전자파학회논문지
• /
• 제30권4호
• /
• pp.261-269
• /
• 2019

본 논문은 레이돔과 같은 다층구조의 주파수 선택적 표면(frequency selective surfaces: FSS)을 설계하는데, 편파나 입사각 등 다양한 고려사항에 대한 유연성을 갖는 픽셀 형태의 주파수 선택적 표면을 설계하는 것에 관한 것이다. 픽셀 형태의 FSS를 설계할 때 이산 공간 문제를 해결할 수 있는 다양한 방법 중 이진 입자 군집 최적화(binary particle swarm optimization: BPSO) 알고리즘은 FSS의 주기구조 패턴을 결정하는데 쉽게 적용 가능한 기술 중 하나이며, 따라서 향상된 BPSO 알고리즘을 통해 롤 오프 전파 투과특성을 갖는 FSS를 효율적으로 설계하는 기법을 제안하였다. 원하는 솔루션에 입자를 유도하기 위한 적합성 함수 설계에 대하여 수렴속도 문제를 해결하기 위해, '기울기'를 입력 변수로 한 적합성 함수를 적용할 경우 쉽게 원하는 전파특성을 갖는 FSS를 얻을 수 있었다.