Inverse tone mapping for bit-depth scalable image coding adapted to variable block sizes

A tone mapping and codec technology, applied in the field of image encoding and decoding, can solve the problem of reducing the quality of inverse tone mapping

Inactive Publication Date: 2008-12-31
MITSUBISHI ELECTRIC CORP
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  • Application Information

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Problems solved by technology

Another disadvantage is that the same scale factor is used for all chroma components
This reduces the quality of the inverse tonemap

Method used

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  • Inverse tone mapping for bit-depth scalable image coding adapted to variable block sizes
  • Inverse tone mapping for bit-depth scalable image coding adapted to variable block sizes
  • Inverse tone mapping for bit-depth scalable image coding adapted to variable block sizes

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Embodiment Construction

[0026] The present invention provides a system and method for converting between bit depth representations of images and video using tone mapping. The bit depth conversion can be from low to high (LDR→HDR) or from high to low (HDR→LDR). Images and video can be either single-channel monochrome or multi-channel color. The block size is variable. This method takes the following parameters: scale factor, offset value, and forecast direction. These parameters are determined for each block of each color channel. We also describe the procedure used to determine the optimal scale factor. Compared to conventional methods of fixing or limiting the set of scale factors, the scale factors of the present invention can be customized and the range of scale factors can be adaptively and dynamically increased to accommodate a larger dynamic range of images. The corresponding offset value and prediction direction are determined according to the scale factor.

[0027] In order to efficientl...

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Abstract

A method and system for inverse tone mapping and decoder. The method performs inverse tone mapping of an image in a decoder. For each block of each color channel of the image the following steps are performed. A scaling factor is determined for a current block of the image by adding a predicted scaling factor for the current block to a difference between the predicted scaling factor and the scaling factor of an adjacent block. An offset value for the current block is determined by adding a predicted offset for the current block to a difference between the predicted offset value and the offsetvalue of the adjacent block. The scaling factor and the offset value are applied to pixel intensity values of the current block to produce a mapped block in which a bit-depth of the mapped block is greater than the bit-depth of the current block.

Description

technical field [0001] The present invention relates generally to the encoding and decoding of images, and more particularly to the encoding and decoding of sequences of images having scalable bit depths. Background technique [0002] In computer graphics, tone mapping alters the dynamic range of an image. For example, tone mapping can convert a high dynamic range (HDR) image to a low dynamic range (LDR) image, or a low dynamic range (HDR) image to a high dynamic range (LDR) image. In images, this dynamic range is determined by the number of bits (bit depth) allocated to store pixel intensity values. Tone mapping attempts to avoid strong contrast reduction from scene luminance values ​​to the renderable range while maintaining the appearance of the image. [0003] Conventional video coding mechanisms (eg, MPEG and the ITU series of video coding standards) are well suited for video compression with a fixed bit depth (eg, 8 bits per pixel (bpp)). Consumer video and digital ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H04N7/26H04N7/32H04N11/04H04N19/593
CPCH04N19/105H04N19/126H04N19/134H04N19/176H04N19/184H04N19/186H04N19/196H04N19/36H04N19/46H04N19/463H04N19/593
Inventor 刘杉安东尼·韦特罗金祐湜
Owner MITSUBISHI ELECTRIC CORP
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