Sisvel Technology S.r.l.

Ecole Polytechnique Federale De Lausanne

Ecole Polytechnique Féderale De Lausanne (epfl)

Giulia Fracastoro

Enrico Magli

Pascal Frossard

Marco Grangetto

Francesco Verdoja

Dorina Thanou

A method and an apparatus for encoding and/or decoding digital images, wherein the encoding apparatus includes a processor configured for determining weights of a graph related to an image by minimizing a cost function, transforming the weights through a graph Fourier transform, quantizing the transformed weights, computing transformed coefficients through a graph Fourier transform of a graph having the transformed weights as weights, de-quantizing the quantized transformed weights, computing a reconstructed image through an inverse graph Fourier transform on the basis of the de-quantized transformed weights, computing a distortion cost on the basis of the reconstructed image and the original image, generating a final encoded image on the basis of the distortion cost.

Techniques for encoding and decoding digital data using graph-based transformations

A method and an apparatus are provided for encoding and/or decoding digital images or video streams. The encoding apparatus includes a processor configured for reading at least a portion of an image (f), determining a rotation angle (&#x3b8;) on the basis of the portion of the image (f), determining rotated transform matrix (V') which is the result of a rotation of at least one basis vector of a Discrete Cosine Transform matrix (V) by the rotation angle (&#x3b8;), computing transformed coefficients (f{circumflex over (&#x2003;)}) on the basis of the pixel values contained in the portion of the image (f) and the rotated transform information (V&#x2032;), outputting the transformed coefficients (f{circumflex over (&#x2003;)}) to the destination.

Apparatuses and methods for encoding and decoding images

A method and an apparatus for encoding and/or decoding digital images or video streams are provided, wherein the encoding apparatus includes a processor configured for reading at least a portion of the image, segmenting the portion of the image in order to obtain groups of pixels identified by borders information and containing at least two pixels having one or more homogeneous characteristics, computing, for each group of pixels, a weight map on the basis of the borders information associated to the group of pixels, a graph transform matrix on the basis of the weight map, and transform coefficients on the basis of the graph transform matrix (U) and of the pixels contained in the group of pixels.

Methods and apparatuses for encoding and decoding digital images through superpixels

Methods and apparatuses for encoding and/or decoding digital images or video streams, wherein the encoding apparatus includes a processor configured for reading a portion of the image (f), computing difference values between pixel values of the image, quantizing such pixel difference values for obtaining a quantized weight map (W), computing an edge map (f') composed by elements (f&#x2032;) indicating whether a corresponding pixel of the portion of the image is an edge or not on the basis of the quantized weight map, determining a reconstructed weight map (W&#x2032;) on the basis of the edge map (f&#x2032;), determining a graph transform matrix (U) on the basis of the reconstructed weight map (W&#x2032;), computing transform coefficients (f{circumflex over (&#x2003;)}) on the basis of the graph transform matrix (U) and said portion of the image (f), transmitting the computed transform coefficients (f{circumflex over (&#x2003;)}) and the edge map (f&#x2032;).

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Turin, Italy

Giulia Fracastoro