Vector representation of binary images has an advantage of keeping high image quality for arbitrary scaling as well as editing capability of an object. However, the vector represen-tation suffers from low compression efficiency compared... more
Vector representation of binary images has an advantage of keeping high image quality for arbitrary scaling as well as editing capability of an object. However, the vector represen-tation suffers from low compression efficiency compared with JBIG. In this paper, we show the main cause reducing coding efficiency and propose two methods to improve it. The pro-posed methods can reduce the file size of a binary image up to about 30–40 percent. Index Terms — Image coding, vectorization, binary im-age, noise reduction, image quality
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HEVC (High Efficiency Video Coding) is an ongoing standardization target as the next generation of video compression technology. HEVC employs a coding tree block, which is a quad-tree structure of a coding unit. It also employs some unit... more
HEVC (High Efficiency Video Coding) is an ongoing standardization target as the next generation of video compression technology. HEVC employs a coding tree block, which is a quad-tree structure of a coding unit. It also employs some unit types; coding unit, prediction unit, and transform unit. A coding unit can be divided into smaller units as prediction units. Though an asymmetric unit is used for inter coding, only symmetric units are permitted for intra coding. In this paper, we propose an asymmetric partitioning with a non-power-of-two transform as a prediction and transform unit. While conventional partitioning locates the cross-point of partitioning lines at the center of the coding unit, the proposed method locates the cross-point in places except center. The proposed method reduces 2.0% BD-bitrate compared with HM5.0 under all intra / high efficiency condition. The validity of the proposed method is confirmed by some experimental results.
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Images containing characters, line drawings, and halftone dots are displayed on many panels which has different resolutions. Resolution conversion of images is mandatory technique to adjust different resolutions. We have proposed to... more
Images containing characters, line drawings, and halftone dots are displayed on many panels which has different resolutions. Resolution conversion of images is mandatory technique to adjust different resolutions. We have proposed to convert raster representation into vector representation. In this paper, we assume an input image is a comic image because it is in great demand for contents, and then we describe a comic image coding system. This system separates the input image into characters, line drawings, and halftone dots. We show a block diagram of the system and describe elemental techniques. Evaluation experiments are done by implementation for PDA.
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Object oriented coding segment an image into regions, which characteristics are coherent. Vector representation is suitable to describe contours of regions in object oriented coding. On the other hand, we have proposed border extraction... more
Object oriented coding segment an image into regions, which characteristics are coherent. Vector representation is suitable to describe contours of regions in object oriented coding. On the other hand, we have proposed border extraction using sub–pixel binarization for the low resolution grayscale image. This image which is originally binary image is obtained as grayscale image by a scanner. In this paper, a target is an image which originally consists of homogeneous regions is obtained as grayscale image containing anti–aliasing. This image is named the “artificial image.” The research object is the image coding based on vector representation. We propose the segmentation method considering characteristics of the artificial image. An “inverse norm” is introduced to achieve the segmentation. Then the segmentation problem is converted to the minimization problem of an object function with the inverse norm. An algorithm to solve the minimization problem is designed. Total variation ima...
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Vector representation of binary images, such as comics, has an advantage of keeping high image quality for arbitrary scaling. Moreover, it has an editing capability at an object basis. However, the vector representation su ffers from... more
Vector representation of binary images, such as comics, has an advantage of keeping high image quality for arbitrary scaling. Moreover, it has an editing capability at an object basis. However, the vector representation su ffers from achieving high compression e fficiency compared with JBIG. We have showed a main cause of coding ine fficiency is redundant passing points by the noise on straight lines and curves. Then, we have described a proposed method to relieve it. In this paper, we aim to evaluate the quality of vectorized binary images which are processed by the method of rate reduction. We consider two techniques to reduce a bit rate for vectorization and to evaluate the quality of vectorized binary images. The former, we indicate the conventional method using Gaussian filter and propose the method for improvement of the coding e fficiency. The latter, for evaluation of the images, we show the method using distortion and propose the method using number of contour lines. Validi...
あらまし 全変動は輝度変化が滑らかであるという仮定を導入することなく画像を扱える正則化基準である. 全変動最小化によって入力画像から骨格成分を取得する手法として,(1) 骨格成分とは双対の関係にある振動成 分に着目し,半陰的再急降下法により解く手法や,(2) ノイズエネルギーが既知の値以下であるという制約条件 付き最小二乗問題と全変動を画像の分類から決定される値にする凸最適化問題の二つを交互に解く手法が提案さ... more
あらまし 全変動は輝度変化が滑らかであるという仮定を導入することなく画像を扱える正則化基準である. 全変動最小化によって入力画像から骨格成分を取得する手法として,(1) 骨格成分とは双対の関係にある振動成 分に着目し,半陰的再急降下法により解く手法や,(2) ノイズエネルギーが既知の値以下であるという制約条件 付き最小二乗問題と全変動を画像の分類から決定される値にする凸最適化問題の二つを交互に解く手法が提案さ れている.しかし,これらの手法は計算コストが高いという問題がある.本論文では,全変動最小化を高速に計 算する手法を提案する.まず,全変動を二次元画像に適用して離散化する際に,平方根計算が必要ないノルムを 用いる.次に,劣こう配を用いた反復処理で骨格成分を計算する.双対変数を計算しないこと,FFTを含む射影 関数や平方根計算が不必要,浮動小数点の計算回数の削減により計算量を削減する.計算時間を従来手法の (1) に対して 53%,(2) に対して 5%へと大幅に削減できることを実験結果により示す.提案手法は従来手法と同等 の性能を維持したまま,陽に忠実化項と平滑化項から構成される反復処理を可能とする. キーワード 全変動最小化,数値計算,画像分解,画像復元,画像処理
Artificial images include a lot of edges and homogeneous tone areas. Mosquito noise and pseudo tone is occurred by the discrete cosine transform and the quantization for such images. It is in H.264/AVC that losing texture and changing... more
Artificial images include a lot of edges and homogeneous tone areas. Mosquito noise and pseudo tone is occurred by the discrete cosine transform and the quantization for such images. It is in H.264/AVC that losing texture and changing edge directions are occurred. We have proposed a still image coding based on vector representation to provide a solution to the above problems. In this paper, we show the cause of losing texture, and thus, we propose video coding method using vector representation. At first, we examine edge area modeling optimized vector representation. Then, we describe the difference between an input signal and low-frequency-component on edge areas using over-sampling and average filter technique. The proposed method keeps the image quality near edge areas. We confirm the validity of the proposed method through some edge detection experiments.
Vectorization is an effective technique for comic image coding, since comics are mainly consist of line drawings. However, an existence of halftone-dots causes an increase of coding bitrate if simple vectorization is used. In addition,... more
Vectorization is an effective technique for comic image coding, since comics are mainly consist of line drawings. However, an existence of halftone-dots causes an increase of coding bitrate if simple vectorization is used. In addition, moires occur when a resolution of the image with halftone-dots is changed. In this paper, we propose a new technique to achieve highly efficient comic image coding. First, we separate the area of halftone-dots and line drawings from an image. Then, a continuous tone approximation is applied to the area of halftone-dots. Next, the conventional vectorization is applied to line drawings. Finally, these two components are mixed together.
A demand for vector representation contents are increasing since viewer environments for vector graphics are disseminated. Then vectorization method to obtain a vector representation form raster representation is a significant technique.... more
A demand for vector representation contents are increasing since viewer environments for vector graphics are disseminated. Then vectorization method to obtain a vector representation form raster representation is a significant technique. In addition, edit–ability, which is facility of curve manipulation, is required. In this paper, we adopt the definition that a summit of the curve is located extremum of curvature using Curvature Scale Space (CSS). Our object is to evaluate the edit–ability of the obtained vector representation by the location of pass point of Bézier curve. We proposed the evaluation method of edit–ability whether a pass point is near the summit. Some experiments clarify that the summit is corresponding to the extrema of curvature. Moreover, out proposed vectorization technique has much part of high facility than the conventional method.
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In this paper, we propose an explicit residual decorrelation method to improve the coding performance for 4:4:4 chroma format conforming HEVC framework. The energy from a residual signal is gathered to the primary component by... more
In this paper, we propose an explicit residual decorrelation method to improve the coding performance for 4:4:4 chroma format conforming HEVC framework. The energy from a residual signal is gathered to the primary component by decorrelation of color space. The transform matrix as decorrelation is derived from reference pixel value by using singular value decomposition for each prediction unit. Since the derivation is applied in both encoder and decoder side, the identical matrix is obtained for both sides. Compared to the previous works, the proposed method applies only for the meaningful unit while an enabled flag is explicitly signaled as side information. The proposed method is implemented on HEVC test model. For the RGB/YUV 4:4:4 chroma format sequences, the coding gains in BD-rate are up to 23.3%/4.9%, respectively. Compared to the result by the previous works, average gains are slightly decreased, while each gain of sequence is always better than that by conventional method.
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The major advantage of vector representation of an im- age is that the image quality is maintained for arbitrary scal- ing. In recent years, a demand for scalable image coding has been increasing because of the wide variety of available... more
The major advantage of vector representation of an im- age is that the image quality is maintained for arbitrary scal- ing. In recent years, a demand for scalable image coding has been increasing because of the wide variety of available digital contents and display terminals. Conventional scal- able coding schemes are based on raster representation, and thus, line drawings deteriorate
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HEVC (High Efficiency Video Coding) is an ongoing standardization target as the next generation of video compression technology. HEVC employs a coding tree block, which is a quad-tree structure of a coding unit. It also employs some unit... more
HEVC (High Efficiency Video Coding) is an ongoing standardization target as the next generation of video compression technology. HEVC employs a coding tree block, which is a quad-tree structure of a coding unit. It also employs some unit types; coding unit, prediction unit, and transform unit. A coding unit can be divided into smaller units as prediction units. Though an asymmetric unit is used for inter coding, only symmetric units are permitted for intra coding. In this paper, we propose an asymmetric partitioning with a non-power-of-two transform as a prediction and transform unit. While conventional partitioning locates the cross-point of partitioning lines at the center of the coding unit, the proposed method locates the cross-point in places except center. The proposed method reduces 2.0% BD-bitrate compared with HM5.0 under all intra / high efficiency condition. The validity of the proposed method is confirmed by some experimental results.
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Inter colour-component correlation is generally very high in RGB 4:4:4 chroma format. To improve the coding performance of the high efficiency video coding (HEVC) especially for such content, we propose the in-loop colour-space-transform.... more
Inter colour-component correlation is generally very high in RGB 4:4:4 chroma format. To improve the coding performance of the high efficiency video coding (HEVC) especially for such content, we propose the in-loop colour-space-transform. The colour space is dynamically transformed into un-correlated space by employing singular value decomposition (SVD) for each block at both the encoder and decoder. Signals in transformed colour space are coded with the existing intra / inter coding framework. We utilize the simplified SVD process implemented only by integer operations for the complexity reduction. Compared with HM10.0 as an anchor method, BD-bitrate gain reached 23.8% and 23.4% for the all intra case and the random access case, respectively, while a runtime of the decoder increase 4.8-9.8%.