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This paper proposes a de-noising method especially for a biased noise. Even though a noise is assumed to have zero mean, an image processing such as tone mapping alters this property. Firstly, a precise estimation of the noise bias caused by a tone mapping function is derived considering discontinuity of a general form of the tone mapping. Secondly, a method of compensating the noise bias is introduced...
This report proposes a two layer lossless coding system for high dynamic range (HDR) images expressed in a floating point data format. Its encoder outputs compressed image data in two layers. From the base layer, a standard low dynamic range (LDR) image is decoded. Merging with the enhancement layer, the original HDR image is decoded without any loss. We introduce a reversible logarithmic mapping...
In this report, we propose a lossy compression algorithm which can utilize the ‘histogram sparseness’ of pixel values of an input image signal. The bit depth of pixel values has becoming longer than conventional ones in high dynamic range images. Their histogram of pixel values tends to be ‘sparse’, — not all the histogram bins are used. We extend an existing lossless coding based on the histogram...
In this paper, a lossy data compression for a sparse histogram image signal is proposed. It is extended from an existing lossless coding which is based on a lossless histogram packing and a lossless coding. We introduce a lossy mapping, which has less computational load than the rate-distortion optimized Lloyd-Max quantization, and combine it with a lossless coding. It was confirmed that the proposed...
In this report, we reduce the number of lifting steps of the two dimensional (2D) discrete wavelet transform (DWT) in JPEG 2000 by introducing a factorization of the separable 2D transfer function into some non separable 2D (NS-2D) functions. The order of the 1D lifting steps in vertical and in horizontal are properly replaced so that all of them are synthesized into NS-2D functions. As a result,...
This report theoretically derives a condition on the word length of coefficients and signals such that the irreversible 9-7 discrete wavelet transform (DWT) in JPEG 2000 becomes lossless for a constant valued (DC) input signal. Under the condition, the output signal contains no error in spite of rounding of coefficients and signals inside the DWT circuit. We have previously analyzed the condition...
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