US 5,546,474 A · Detection of photo regions in digital images

Abstract

A method for classifying regions in a digital image as either photo regions or non-photo regions is presented. A digital image is divided into regions and each region is divided into a plurality of cells. Each cell comprises a group of pixels represented by one or more digital bits. Features of a cell such as its graylevel spread, or the moment of inertia of its co-occurrence matrix, are used to determine the likelihood that the cell is a photo cell or a non-photo cell. Based on this likelihood, the cell is classified as either a photo cell, a non-photo cell, or is unclassified. Classified cell is used in conjunction with unclassified cells to grow regions that can be characterized as photo regions or non-photo regions. Once a region is classified as a photo region or a non-photo region a decision is made regarding the number of bits per pixel needed to adequately represent that region.

Claims19

Dependent claims

A method for classifying a region in a digital image as either a photo region or a non-photo region, wherein each region comprises a plurality of cells, the method comprising the steps of:

(a) extracting one or more features about each of said plurality of cells, wherein said one or more features indicate a likelihood that said cell is a photo cell, including the step of:
(I) determining a moment of inertia about a main diagonal of a co-occurrence matrix of said cell, including the steps of:
(1) constructing a co-occurrence matrix for each of said cells, said co-occurrence matrix having elements representing a number of times a pixel having a first graylevel is adjacent to a pixel having a second graylevel, and
(2) determining a moment of inertia of said co-occurrence matrix, said moment of inertia indicating an amount of graylevel transitions;
(b) determining whether each of said cells is likely to be a photo cell based on said one or more features extracted in step (a);
(c) labeling each of said cells as either a photo cell or a non-photo cell, or an unclassified cell, said classification based on the result of said step (b);
and
(d) growing region as either photo regions or non-photo regions using said cells.

5 more elements

A method for classifying a region in a digital image as either a photo region or a non-photo region, wherein each region comprises a plurality of cells, each of said plurality of cells comprising pixels, each of said pixels represented by one of a plurality of graylevels, the method comprising the steps of:

(a) extracting one or more features about each of said plurality of cells, wherein said one or more features indicate a likelihood that said cell is a photo cell, and further wherein said one or more features include a graylevel spread for said cell, including the step of:
(i) constructing a graylevel histogram indicating the number of pixels in each of said plurality of cells that are in each graylevel, and
(ii) determining a graylevel spread for each of said plurality of cells, including the steps of:
(1) determining which graylevels of said graylevel histogram represent peak, and which graylevels represent valleys,
(2) determining a subpopulation for each peak of said graylevel histogram,
(3) determining a probability of each subpopulation,
(4) determining a spread of each population,
(5) determining a separation indication of each subpopulation, and
(6) determining said graylevel spread of said graylevel histogram using said probability of each subpopulation, said spread of each subpopulation, and said separation indication of each subpopulation;
(b) determining whether each of said cells is likely to be a photo cell based on said one or more features extracted in step (a);
(c) labeling each of said cells as either a photo cell, a non-photo cell, or an unclassified cell, said classification based on the result of step (b);
and
(d) growing regions as either photo regions or non-photo regions using said cells.

10 more elements

Dependencies are inferred from the claim text.

Detection of photo regions in digital images

Life of this patent

Detection of photo regions in digital images

Life of this patent

Abstract

Claims19