 ISL to TTL translator |
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| Apparatus for processing image motion compensation information for an image processing system |
| It is an object of the present invention to provide an apparatus for processing image motion ... |
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| Digital image processor for color image compression |
| The objects of this invention are accomplished by rearranging the DCT process such that non-trivial ... |
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| Line standard conversion circuit |
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| SECAM Color identifying circuit |
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| TDM Scheme for digital video processing |
| FIG. 1 shows a block diagram of a system in accordance with the invention. A video signal source 10... |
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| Voltage controlled resonant transmission semiconductor device |
| Having thus described our invention, what we claim as new and desire to secure by Letters Patent is:... |
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| Motion adaptive interpolation of television image sequences |
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| Power semiconductor component for cooling by boiling or liquids |
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| Method for measuring of chromatic optical density |
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DCT transform compression, transmission and recovery of digital color using virtual filtering mechanism
| Details |
Inventors: Daly, Scott J.; Granger, Edward M.;
Assignee: Eastman Kodak Company (Rochester, NY)
Primary Examiner: Britton; Howard W.
Assistant Examiner:
Attorney, Agent or Firm: Dugas; Edward
A color imagery compression/decompression mechanism employs a contrast sensitivity function model of the human visual system for color images, to derive normalization values for compressing chromatic components of the color imagery data. The CSF model is defined in terms of an ADT color space transform (15), the chromatic channels of which conform with the band-limited sensitivity of the visual system. The transform for obtaining the ADT components is executable by reduced complexity logic operators. Each of the ADT components is block transform coded using DCT transform coefficients (18) that are normalized (24) in accordance with a `weighted` (46, 45) CSF model (42) of the human visual system, which effectively performs a low pass filtering of the chromatic (DT) channels. This low pass filter-weighting of the normalization values in the compression, transmit end (10) of the system produces a set of normalized coefficients which effectively blur the image and reduce the entropy in the chromatic channels and may be implemented using a Gaussian function. In the decompression process at the receiver (14), a corresponding set of denormalization coefficients (32), which are generated in accordance with the same chromatic CSF model of the human visual system, are not weighted, so that the cascading of the normalization and denormalizing operators in the transmitter and receiver yields a product less than unity, simulating the entropy-reducing effect of subsampling. |
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DETAILED DESCRIPTION In accordance with the present invention, the benefits of using a model of the human visual system to normalize the transform coefficients of the DCT operator for a monochromatic image are extended to a color image signal processing, without having to actually perform filtering and subsampling, so that the above mentioned hardware penalty is not imposed on the signal processor.
In particular, the present invention is directed to a mechanism which employs a contrast sensitivity function (CSF) model of the human visual system for color images, to derive normalization values to be used in the compression of chromatic components, as well as the achromatic component, of the color imagery data.
The CSF model is defined in terms of a color space transform, the chromatic channels of which have a bandwidth that is considerably less than that of the RGB signal components, so that the transformed signals conform with the band-limited sensitivity of the visual system.
In particular, the color transform is defined by a transform coordinate system containing achromatic (A), deuteranopic (D) and tritanopic (T) axes.
Advantageously, the coefficients of the transform for obtaining the ADT components from the RGB signals employs a set of conversion coefficients, absolute values of which are related to one another in powers of two, so that the original RGB signals can be transformed into the ADT color space by reduced complexity logic operators (shift and add).
Each of the color-converted A, D and T components is block transform coded using DCT transform coefficients that are normalized in accordance with a `weighted` CSF model of the human visual system, which effectively performs a low pass filtering of the chromatic channels (the D and T components) of the input color imagery data.
This low pass filter-weighting of the normalization values in the compression/transmit end of the system produces a set of normalized coefficients which effectively blur the chromatic components of the image and reduce the entropy in the chromatic channels
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Image Analysis 
