US 5,293,228 AGranted

Method for the coding of color images at high compression rate without filtering, corresponding decoding method, coder, decoder and applications

AssigneesFrance Telecom, Telediffusion de France

InventorBernard Marti

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Abstract

A method for the coding of images represented by source signals by means of which a luminance signal is formed by linear combination, using positive coefficients of the source signals, and at least one color signal, the luminance and color signals being digitized, sampled at the same resolution, and subjected to a reversible mathematical transformation in the frequency domain. The method comprises the steps of quantizing and assigning a code value to the continuous component and to each component of a set of alternating components of the transformed luminance signal, and quantizing and assigning a code value to only the continuous component of each of the transformed color signals, a set of alternating components being reconstructed by estimation during the decoding for each of the transformed color signals. The method can be applied to color images of any type represented as the superimposition of monochromatic images, whether the images are still images or motion images.

Claims20

Dependent claims

A method for the coding of color images represented by at least two source signals comprising the following steps:

forming a luminance signal, by linear combination of said at least two source signals, using positive coefficients;
forming at least one color signal, from at least one of said source signals;
digitizing said luminance signal and said at least one color signal, so as to form a digitized luminance signal and at least one digitized color signal;
sampling said digitized luminance signal and said at least one digitized color signal, so as to form a sampled luminance signal and at least one sampled color signal;
subjecting said sampled luminance signal and said at least one sampled color signal to a reversible mathematical transformation in the frequency domain, associating to said sampled luminance signal a transformed luminance signal and associating to each said at least one sampled color signal a corresponding transformed color signal, each of said transformed luminance signal and said at least one transformed color signal comprising a series of components consisting of one continuous component and of alternating components;
quantizing and assigning a code value to the continuous component and to each component of a set of the alternating components of the transformed luminance signal to provide a coded continuous component and a set of coded alternating components of the transformed luminance signal;
and
quantizing and assigning a code value to only the continuous component of each said at least one transformed color signal to provide a coded continuous component of each of said at least one transformed color signal.

5 more elements

A coder of color image signals represented by at least two source signals comprising:

means for forming a luminance signal, by linear combination of said at least two source signals, using positive coefficients, and forming at least one color signal;
means for digitizing said luminance signal and said at least one color signal to form a digitized luminance signal and at least one digitized color signal;
means for sampling said digitized luminance signal and said at least one digitized color signal to form a sampled luminance signal and at least one sampled color signal;
means for subjecting said sampled luminance signal and said at least one sampled color signal to a reversible mathematical transformation in the frequency domain to associate said sampled luminance signal to a transformed luminance signal and to associate each said at least one sampled color signal to a corresponding transformed color signal, each said transformed luminance signal and said at least one transformed color signal comprising a series of components consisting of one continuous component and alternating components;
means for quantizing and assigning a code value to the continuous component and to each component of a set of the alternating components of the transformed luminance signal to form a coded continuous component and a set of coded alternating components of the transformed luminance signal;
and
means for quantizing and assigning a code value to only the continuous component of each said at least one transformed color signal to form a coded continuous component of each said at least one transformed color signal.

4 more elements

A method for the decoding of coded color image signals comprising a first set of code values corresponding to the continuous component and to each component of a set of alternating components of a transformed luminance signal and to only the continuous component of each at least one transformed color signal, the method comprising the steps of:

decoding and dequantizing each code value of said first set of code values, providing both a decoded continuous component and a set of decoded alternating components of said transformed luminance signal and only a decoded continuous component of each said at least one transformed color signal;
and
estimating a set of estimated alternating components of each said at least one transformed color signal, as a function of said set of decoded alternating components of said transformed luminance signal and of the decoded continuous components of said transformed luminance signal and of said at least one transformed color signal.

Dependencies are inferred from the claim text.