An image coding method using DCT in skew coordinates

Yamane, Nobumoto; Morikawa, Yoshitaka; Nariai, Takeshi; Tsuruhara, Atsushi

doi:10.1002/(sici)1520-6424(200001)83:1<53::aid-ecja6>3.0.co;2-5

Cited by 4 publications

(1 citation statement)

References 5 publications

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“…More related to our current work is the so-called skew coordinates DCT (SC-DCT) developed in [27] and [28]. In addition to the square block shape , SC-DCT defines three new block shapes: rectangle, triangle, and rhombus, where two triangular shapes of two neighboring blocks will be merged into a rhombus if their directions agree with each other.…”

Section: Introductionmentioning

confidence: 99%

Directional Discrete Cosine Transforms—A New Framework for Image Coding

Zeng

2008

IEEE Trans. Circuits Syst. Video Technol.

145

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Nearly all block-based transform schemes for image and video coding developed so far choose the 2-D discrete cosine transform (DCT) of a square block shape. With almost no exception, this conventional DCT is implemented separately through two 1-D transforms, one along the vertical direction and another along the horizontal direction. In this paper, we develop a new blockbased DCT framework in which the first transform may choose to follow a direction other than the vertical or horizontal one. The coefficients produced by all directional transforms in the first step are arranged appropriately so that the second transform can be applied to the coefficients that are best aligned with each other. Compared with the conventional DCT, the resulting directional DCT framework is able to provide a better coding performance for image blocks that contain directional edges-a popular scenario in many image signals. By choosing the best from all directional DCTs (including the conventional DCT as a special case) for each image block, we will demonstrate that the rate-distortion coding performance can be improved remarkably. Finally, a brief theoretical analysis is presented to justify why certain coding gain (over the conventional DCT) results from this directional framework.Index Terms-Directional discrete cosine transform, discrete cosine transform (DCT), image coding, video coding.

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Section: Introductionmentioning

confidence: 99%

Directional Discrete Cosine Transforms—A New Framework for Image Coding

Zeng

2008

IEEE Trans. Circuits Syst. Video Technol.

145

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Generalized Zigzag Scanning Algorithm for Non-square Blocks

Ding

Lin

Chen

2011

Lecture Notes in Computer Science

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Two-Dimensional Orthogonal DCT Expansion in Trapezoid and Triangular Blocks and Modified JPEG Image Compression

Ding

Huang

Lin

et al. 2013

IEEE Trans. on Image Process.

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In the conventional JPEG algorithm, an image is divided into eight by eight blocks and then the 2-D DCT is applied to encode each block. In this paper, we find that, in addition to rectangular blocks, the 2-D DCT is also orthogonal in the trapezoid and triangular blocks. Therefore, instead of eight by eight blocks, we can generalize the JPEG algorithm and divide an image into trapezoid and triangular blocks according to the shapes of objects and achieve higher compression ratio. Compared with the existing shape adaptive compression algorithms, as we do not try to match the shape of each object exactly, the number of bytes used for encoding the edges can be less and the error caused from the high frequency component at the boundary can be avoided. The simulations show that, when the bit rate is fixed, our proposed algorithm can achieve higher PSNR than the JPEG algorithm and other shape adaptive algorithms. Furthermore, in addition to the 2-D DCT, we can also use our proposed method to generate the 2-D complete and orthogonal sine basis, Hartley basis, Walsh basis, and discrete polynomial basis in a trapezoid or a triangular block.

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An image coding method using DCT in skew coordinates

Cited by 4 publications

References 5 publications

Directional Discrete Cosine Transforms—A New Framework for Image Coding

Directional Discrete Cosine Transforms—A New Framework for Image Coding

Generalized Zigzag Scanning Algorithm for Non-square Blocks

Two-Dimensional Orthogonal DCT Expansion in Trapezoid and Triangular Blocks and Modified JPEG Image Compression

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