The color appearance of an object depends on its reflectance spectrum and on the spectral characteristic of the illumination. In order to offer correct color under different illuminations at the reproduction stage it ...
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ISBN:
(纸本)0819424293
The color appearance of an object depends on its reflectance spectrum and on the spectral characteristic of the illumination. In order to offer correct color under different illuminations at the reproduction stage it is necessary to transmit information about the whole reflectance spectrum. Knowing the tristimulus color values for a set of illuminations it is possible to calculate a reflectance spectrum that leads to the desired colors for these illuminations and linear combinations of them. The relatively small changes in color with changing illumination allow the use of a DPCM coding scheme. The performance is improved by predicting the color appearance of the object from one illumination to another. To achieve this we employ the white adaptation mechanism of the human eye and extend this by statistical modeling of the underlying reflectance spectra. We evaluate our approach using a set of reflectance spectra as well as a multispectral image.
This paper describes a technique for performing intra prediction of the chroma planes based on the reconstructed luma plane in the frequency domain. This prediction exploits the fact that while RGB to YUV color conver...
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ISBN:
(纸本)9781628415001
This paper describes a technique for performing intra prediction of the chroma planes based on the reconstructed luma plane in the frequency domain. This prediction exploits the fact that while RGB to YUV color conversion has the property that it decorrelates the color planes globally across an image, there is still some correlation locally at the block level. Previous proposals compute a linear model of the spatial relationship between the luma plane (Y) and the two chroma planes (U and V).(2) In codecs that use lapped transforms this is not possible since transform support extends across the block boundaries(3) and thus neighboring blocks are unavailable during intra-prediction. We design a frequency domain intra predictor for chroma that exploits the same local correlation with lower complexity than the spatial predictor and which works with lapped transforms. We then describe a low-complexity algorithm that directly uses luma coefficients as a chroma predictor based on gain-shape quantization and band partitioning. An experiment is performed that compares these two techniques inside the experimental Daala video codec and shows the lower complexity algorithm to be a better chroma predictor.
This paper presents an efficient fractal coding scheme for colorimages and demonstrates its experimental results. The proposed fractal coding scheme utilizes the correlation between a luminance component (Y) and two ...
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ISBN:
(纸本)0819450235
This paper presents an efficient fractal coding scheme for colorimages and demonstrates its experimental results. The proposed fractal coding scheme utilizes the correlation between a luminance component (Y) and two color difference components (Cr and Cb) of an input colorimage. The Y, Cr and Cb components are first decomposed to low and high frequency sub-band images. Fractal block coding is performed only on the lowest frequency sub-band images of Y, Cr and Cb. The other high frequency sub-band images are encoded by vector quantization (VQ). In the fractal coding process for Y, each range block is encoded by a set of contractive affine transformations of its correspondent domain block. For Cr and Cb, on the other hand, only the range block average values are coded. The other fractal coded data of the correspondent range block of Y are applied also to Cr and Cb. The computer simulation experimental results show that the coded and decoded colorimages obtained by the proposed scheme give higher SNR values and better image qualities compared to the conventional fractal coding scheme and JPEG.
The coding of colorimages is usually confined to coding the color appearance for the illumination present at acquisition time. However, an exact reconstruction of a coded and transmitted document should produce the s...
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ISBN:
(纸本)0819420328
The coding of colorimages is usually confined to coding the color appearance for the illumination present at acquisition time. However, an exact reconstruction of a coded and transmitted document should produce the same color appearance as the original under variable illuminations. In this work we develop a representation of the necessary information to ensure such a color constancy. The only precondition is the absence of mutual illumination as a small but reasonable restriction to the type of illumination. The proposed image representation is developed to a complete image coder concept. Using this concept a hierarchical image description is achieved introducing a minimal color difference.
A new way of reordering spatial orientation tree of SPIHT for improving compression efficiencies for monochrome and colorimages has been proposed. Reordering ensures that SPIHT algorithm codes more significant inform...
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A new way of reordering spatial orientation tree of SPIHT for improving compression efficiencies for monochrome and colorimages has been proposed. Reordering ensures that SPIHT algorithm codes more significant information in the initial bits. List of insignificant pixels and sets are initialized with fewer number of coefficients compared to conventional SPIHT for monochrome images. For colorimages an altered parent offspring relationship and an extra level of wavelet decomposition on chrominance planes were performed. PSNR improvement of 32.06% was achieved at 0.01 bpp for monochrome images and 19.76% for colorimages at 0.05 bpp compared to conventional schemes. (C) The Authors. Published by Elsevier B.V.
In [1], image adaptive linear minimum mean squared error (LMMSE) filtering was proposed as an enhancement layer color image coding technique that exploited the statistical dependencies among the luminance/chrominance ...
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ISBN:
(纸本)0819456586
In [1], image adaptive linear minimum mean squared error (LMMSE) filtering was proposed as an enhancement layer color image coding technique that exploited the statistical dependencies among the luminance/chrominance or Karhunen Loeve Transform (KLT) coordinate planes of a lossy compressed colorimage to enhance the red, blue, green (RGB) color coordinate planes of that image. In the current work, we propose the independent design and application of LMMSE filters on the subbands of a colorimage as a low complexity solution. Towards this end, only the coordinates of the neighbors of the filtered subband coefficient, that are sufficiently correlated with the corresponding coordinate of the filtered subband coefficient, are included in the support of the filter for each subband. Additionally, each subband LMMSE filter is selectively applied only on the high variance regions of the subband. Simulation results show that, at the expense of an insignificant increase in the overhead rate for the transmission of the coefficients of the filters and with about the same enhancement gain advantage, subband LMMSE filtering offers a substantial complexity advantage over fullband LMMSE filtering.
In this work a new model for colorimage compression is introduced. The model predicts the expected distortion in compressed images as a function of the compression rate, known as a Rate-Distortion curve. Based on the...
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ISBN:
(纸本)9780889865914
In this work a new model for colorimage compression is introduced. The model predicts the expected distortion in compressed images as a function of the compression rate, known as a Rate-Distortion curve. Based on the model, we present anon-linear optimization problem, from which the optimal color components and rate allocation are derived. We extend the problem to consider down-sampling of the color components. We show that the rate-distortion model in conjunction with the probability distribution of subband coefficients can be used to develop an efficient algorithm for codingcolorimages. We demonstrate this approach for the Discrete Cosine Transform (DCT) and the Laplacian distribution as the probability model. We measure the distortion using Mean Square Error (MSE) and Weighted Mean Square Error (WMSE). Simulation results are presented and discussed to support the efficiency of the new algorithm.
This paper proposes a novel lossless coding scheme for color still images. The scheme employs a block-adaptive intercolor prediction technique to remove both spatial and spectral redundancy in RGB color signals. The r...
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ISBN:
(纸本)9781424414369
This paper proposes a novel lossless coding scheme for color still images. The scheme employs a block-adaptive intercolor prediction technique to remove both spatial and spectral redundancy in RGB color signals. The resulting prediction errors are encoded using a context-adaptive arithmetic coding method. Several coding parameters which must be encoded as side information are iteratively optimized for each color signal. Experimental results show that the inter-color prediction technique provides better coding performance than a simple combination of reversible color transformation and intra-color prediction techniques.
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