COLOR IMAGE PROCESSING METHOD

Abstract: A color image processing method is provided. The color image processing method includes the step of: (a) indexing a color image by assigning representative colors of an image to a color space divided into a plurality of regions. The color image processing method may be applied to object-based image processing such as MPEG-7, and a fast search and retrieval of multimedia contents can be made.

Description: COLOR IMAGE PROCESSING METHOD Technical Field The present invention relates to a color image processing method, and more particularly, to a method for indexing a color image so that searching for a color image can be efficiently performed. The present invention also includes a color image searching method for searching an image corresponding to a query image in a database indexed by the color image processing method. Background Art According to conventional color image processing methods, one color is expressed as one vector in a three-dimensional (hereinafter referred to as a 3-D) color space composed of three axes ranging from 0 to 255. Thus, each pixel in an image is expressed as one of 256x256x256 values. That is, a database must have 256x256x256 storage places so as to store a color feature vector of the image in the database. Also, in a matching process, searching of 256x256x256 values may have to be performed. Thus, according to the conventional color image processing methods, a large capacity database is required, and it takes much time to search a desired image from the database. Disclosure of the Invention To solve the above problems, it is an object of the present invention to provide a color image processing method capable of indexing a color image and fast search and retrieval of a desired image by using a small capacity database. It is another object of the present invention is to provide a medium for storing a program performing the color image processing method. It is still another object of the present invention is to provide a color image searching method for searching a desired image in the color image indexed according to the color image processing method. It is yet still another object of the present invention is to provide a medium for storing a program performing the color image searching method Accordingly, to achieve the above object, according to one aspect of the present invention, there is provided a color image processing method The color image processing method comprises the step of (a) indexing a color image by assigning representative colors of an image to a color space divided into a plurality of regions It is preferable that the color image processing method further comprises the step of (pa-1 ) obtaining the representative colors of the image and their ratio It is also preferable that the ratio is a percentage Preferably, the color image processing method further comprises the step of (b) storing a region identifier expressing the representative colors, their ratio, and serial numbers of an image and a region in a database as data Preferably, the image is one region selected from divided regions Also, the color space is preferably a 3-D color space In order to achieve the above objects according to another aspect of the present invention, there is provided a color image processing method The color image processing method comprises the steps of (a-1 ) obtaining a feature vector F expressed as an /-th representative color c, and as its ratio p, when N is the number of representative colors in the divided regions of an image, and / is an integer between 1 and N F= { 1 , , Λ/}, (a-2) indexing the image by assigning the representative colors to lattice points of a color space having a lattice structure, and (a-3) storing indexed results in a database having the form of a separate table In order to achieve another object, there is provided a medium for storing a program performing a color image processing method for indexing an image The media comprises the steps of (a-1 ) obtaining a feature vector F expressed as an /-th representative color c, and as its percentage p, when N is the number of representative colors in the divided regions of an image, and / is an integer between 1 and N F= { 1 , Λ/}, (a-2) indexing the image by assigning the representative colors to lattice points of a 3-D color space divided into a plurality of regions, and (a-3) storing indexed results in a database having the form of a separate table In order to achieve still another object, according to one aspect of the present invention, there is provided a color image searching method for searching an image in the database based on a color feature of a query image The color image searching method comprises the step of (a) performing a search based on representative colors of a query image and their ratio in the database indexed by assigning the representative colors of a database image to a color space divided into a plurality of regions The color space is preferably a 3-D color space It is preferable that the step (a) comprises the steps of (a-1 ) obtaining representative colors of a given query image and their ratio, (a-2) selecting a region corresponding to the representative color obtained in the step (a-1 ) in a color space divided into a plurality of regions, (a-3) selecting a data group indexed into the region selected from a database, and (a-4) identifying matched data in which the difference in the ratio of the representative color of the query image is less than a predetermined threshold value in the selected data group It is also preferable that the step (a) further comprises the steps of (a-5) obtaining the sum of the ratio of same regions from the identified data, and (a-6) determining the region in which the difference between the sum of the obtained ratio and the sum of the ratio to the query image is less than a predetermined threshold value as a searched image Preferably, the color image searching method further comprises the step of performing the steps in the color space with respect to neighboring peripheral regions in the case where there are no regions determined as the searched image Preferably, the query image is one region of the image divided into a plurality of regions and the searched image is one region of the database image divided into a plurality of regions In order to achieve still another object, according to another aspect of the present invention, there is provided a color image searching method for searching an image in the database based on a color feature of a query image The color image searching method comprises the steps of (a-1 ) obtaining representative colors of given query regions and their ratio, (a-2) selecting a lattice point corresponding to the representative color obtained in the step (a-1 ) in a 3-D color space divided into a plurality of lattices, (a-3) selecting a data group corresponding to the lattice point selected from the database in which a region identifier expressing representative colors of data images, their ratio, and serial numbers of an image and a region is stored as data, (a-4) identifying matched data in which a difference in the ratio of the representative color of the query regions is less than a predetermined threshold value in the selected data group, (a-5) obtaining the sum of the ratio of same regions from the identified data, and (a-6) determining the regions in which the difference between the sum of the obtained percentages and the sum of the ratio of the query regions is less than a predetermined threshold value as a searched image In order to achieve yet still another object, there is provided a medium for storing a program performing a color image searching method The medium comprises the steps of (a-1 ) obtaining representative colors of given query regions and their ratio, (a-2) selecting a lattice point corresponding to the representative color obtained in the step (a-1 ) in a 3-D color space divided into a plurality of lattices, (a-3) selecting a data group corresponding to the lattice point selected from the database in which a region identifier expressing representative colors of data images, their ratio, and serial numbers of an image and a region is stored as data, (a-4) identifying matched data in which the difference in the ratio of the representative color of the query regions is less than a predetermined threshold value in the selected data group, (a-5) obtaining the sum of the ratio of same regions from the identified data, and (a-6) determining the regions in which the difference between the sum of the obtained percentages and the sum of the ratio of the query regions is less than a predetermined threshold value as a searched image Brief Description of the Drawings The above objects and advantages of the present invention will become more apparent by describing in detail a preferred embodiment thereof with reference to the attached drawings in which FIG 1 is a flowchart illustrating a color image processing method according to a preferred embodiment of the present invention, FIG 2 illustrates one feature vector extracted from one region of an image, FIG 3 illustrates a 3-D color space having a lattice structure, FIG 4 illustrates a database having the form of a separate table used for the color image processing method of FIG 1 , and FIG 5 is a flowchart illustrating a color image searching method according to the preferred embodiment of the present invention Best mode for carrying out the Invention Referring to FIG 1 , which illustrates a flowchart of a color image processing method according to a preferred embodiment of the present invention, first, representative colors and their distribution are identified in the regions of an image (step 102) Here, a percentage can be used for the distribution, and the percentage can be understood as a value in which the number of corresponding pixels is divided by the number of the entire pixels by corresponding representative colors and multiplied by 100 The identified representative colors and their percentages can be expressed as a feature vector That is, when N is the number of representative colors in the regions and / is an integer between 1 and N, the feature vector F expressed as an /-th representative color c, and as its percentage p, is obtained by the following equation (step 104) Referring to FIG 2, which illustrates one feature vector extracted from one region of an image, the feature vector F of a first region R 1 in an arbitrary image is expressed as a first representative color c 1 and its percentage p 1t a second representative color c 2 and its percentage p 2 , and a third representative color c 3 and its percentage p 3 Likewise, the feature vector of other regions R 2 , R 3 , and R 4 can also be expressed Subsequently, the image is indexed by assigning the representative colors to lattice points of a 3-D color space having a lattice structure, and indexed results are stored in a database having the form of a separate table (step 106) The indexed results include a region identifier expressing the representative colors, their ratio, and serial numbers of an image and a region Referring to FIG 3, which illustrates a 3-D color space having a lattice structure, the 3-D color space composed of coordinate axes L, U, and V has a lattice structure Each lattice has lattice points n 1t n 2 , n 3 , n 4 , n 5 , and n 6 in its center, and colors belonging to the range of this lattice are indexed into these lattice points Now, an assumption is made that the first representative color c, is included in the lattice having a first lattice point n_, and the second representative color c 2 is included in the lattice having a (k-1 ) th lattice point n k ή , and the third representative color c 3 is included in the lattice having a third lattice point n 3 Each representative color and its percentages are stored in the database having the form newly-defined in a color image processing method according to the present invention The database is classified into the storage places in which data corresponding to the lattice points n 1t n 2 , n 3 , ,n k 1t and n k are stored This database is formed of a separate table, because the data expressing representative colors of each region and their percentages are separated and stored FIG 4 illustrates a database having the form of a separate table used for the color image processing method of FIG 1 Now the representative colors and their percentages are stored with a region identifier expressing each serial number of an image and a region in the places corresponding to lattice points to which the representative colors belong Then, the data expressing the first representative color c< and its percentage p 1 are stored in the places corresponding to the first lattice point n ή together with the region identifier \D< Also, the data expressing the second representative color c 2 and its percentage p 2 are stored in the places corresponding to the (k-1) th lattice point n k 1 Furthermore, the third representative color c 3 and its percentage p 3 are stored in the places corresponding to the third lattice point n 3 Here, region identifiers ID * , ID 2 , and ID 3 only express the same region of same image In other words, referring to the database shown in FIG 4 the first lattice point n * corresponds to data ID<, c 1r and p t , the third lattice point n 3 corresponds to daia ID 3 , c 3 , and p 3 and the (k-1) th lattice point n k 1 corresponds to data ID 2 , c 2 , and p 2 According to the above color image processing method, an image is indexed by assigning the representative colors of the image to a color space divided into a plurality of regions Accordingly, the database size for storing an index information of an image is relatively small The color image indexed by the above color image processing method can efficiently search similar images to a query image, an image which a user wishes to search by the color image searching method according to the present invention Referring to FIG 5, which illustrates a flowchart of a color image searching method according to the preferred embodiment of the present invention, first, query regions, an original image which a user wishes to search in a database are determined Subsequently, representative colors of the determined query regions and their percentages are identified (step 502) The step 502 is same as the step 102 in the color image processing method shown in FIG 2 Here, the percentages can be understood as values in which the number of corresponding pixels is divided by the number of the entire pixels by corresponding representative colors and multiplied by 100. After that, a lattice point corresponding to each representative color identified is selected (step 504). As shown in FIG. 3, a number of the representative colors are included in one region having the form of a lattice, and a 3-D color space in which lattice points for distinguishing the region exist in the center of the region is assumed. That is, the identified representative colors have the regions to which the colors belong in the 3-D color space. Accordingly, the lattice points, center points of the regions, can be selected. Also, in order to eliminate false matches, it is more preferable to consider the representative colors and their distribution, that is, their percentages together. Accordingly, a data group corresponding to the selected lattice point from the database is selected (step 506), and matched data in which the difference in the percentages of the representative colors of the query regions is less than a predetermined threshold value in the selected date group are identified (step 508). For example, assuming that 30% or so of one representative color of the representative colors in the query regions is included in the query regions, and the predetermined threshold value is 5%, data which correspond to the same lattice point as one representative color selected from the query regions and ± 5% of 30%, the percentage of one representative color selected from the query regions, that is, 25% to 35% data are determined as the matched data. After that, the sum of the percentages of same regions among the matched data is obtained (step 510). In other words, the data expressed as same regions by the region identifier among data determined as the matched data are sorted and the sum of the percentages with respect to the sorted data is obtained. Subsequently, the regions in which the difference between the sum of the percentages obtained in the step 510 and the sum of the percentages of the query regions is less than a predetermined threshold value are determined as searched regions (step 512). As an alternative to this, it is possible to determine a small number of regions in which there is the least difference aligning according to the difference in the percentages as the searched regions or to determine only one region in which there is a minimum difference in the percentages as the searched region However, according to this method, for example, in the case where the representative colors of the query regions are located at an outer area in the lattice, there is a possibility that the regions having similar colors to the representative colors belong to another lattice, and then, the regions may be not searched Accordingly, in the case where there are no regions determined as the searched regions, it is more preferable to perform steps 506 through 512 with respect to peripheral lattice points of the lattice point used for performing a search before (step 514) According to the above-described color image processing method and color image searching method can be used for a computer program Codes and code segments constituting the program can be easily inferred by a skilled computer programmer in the art Also, the program is stored in computer readable media, read and executed by a computer, and it can thereby realize the color image processing method The media include magnetic media, optical media, and carrier waves As described above, according to the present invention, the color image processing method may be applied to object-based image processing, and a fast search and retrieval of multimedia contents can be made Industrial Applicability According to the above-described color image searching method, due to the small size of a database the search speed can be fast , and the search can be efficiently made by not classifying images unnecessarily in detail Further, the above color image searching method may be applied to object-based image processing, and a fast and efficient search and retrieval of multimedia contents can be made

Claims: What is claimed is 1 A color image processing method for indexing an image comprising the step of (a) indexing a color image by assigning representative colors of an image to a color space divided into a plurality of regions 2 The color image processing method according to claim 1 , further comprising the step of (pa-1) obtaining the representative colors of the image and their ratio 3 The color image processing method according to claim 2, wherein the ratio is a percentage 4 The color image processing method according to at least one of claim 2 or claim 3, further comprising the step of (b) storing a region identifier expressing the representative colors, their ratio, and serial numbers of an image and a region in a database as data 5 The color image processing method according to one of claims 1 through 3, wherein the image is one region selected from divided regions 6 The color image processing method according to claim 4, wherein the image is one region selected from divided regions 7 The color image processing method according to at least one of claims 1 through 3 or claim 6, wherein the color space is a three- dimensional color space 8 The color image processing method according to claim 4, wherein the color space is a three-dimensional color space 9 The color image processing method according to claim 5 wherein the color space is a three-dimensional color space 10 A color image processing method for indexing an image, comprising the steps of (a-1 ) obtaining a feature vector F expressed as an /-th representative color c, and as its ratio p, when N is the number of representative colors in the divided regions of an image, and / is an integer between 1 and N (a-2) indexing the image by assigning the representative colors to lattice points of a color space having a lattice structure, and (a-3) storing indexed results in a database having the form of a separate table 11 The color image processing method according to claim 10, wherein the ratio is a percentage 12 The color image processing method according to at least one of claim 10 or claim 11 , wherein the indexed results include a region identifier expressing the representative colors, their ratio, and serial numbers of an image and a region 13 The color image processing method according to at least one of claim 10 or claim 11 , wherein the image is one region selected from divided regions 14 The color image processing method according to claim 12, wherein the image is one region selected from divided regions 15 The color image processing method according to at least one of claim 10, claim 11 , or claim 14, wherein the color space is a three- dimensional color space 16 The color image processing method according to claim 12, wherein the color space is a three-dimensional color space 17 The color image processing method according to claim 13, wherein the color space is a three-dimensional color space 18 A medium for storing a program performing a color image processing method for indexing an image, comprising the steps of (a-1 ) obtaining a feature vector F expressed as an /-th representative color c, and as its percentage p, when N is the number of representative colors in the divided regions of an image, and / is an integer between 1 and N F= { {c„p},ι= , , Λ/}, (a-2) indexing the image by assigning the representative colors to lattice points of a 3-D color space divided into a plurality of regions, and (a-3) storing indexed results in a database having the form of a separate table 19 The medium according to claim 18, wherein the indexed results include a region identifier expressing the representative colors, their ratio, and serial numbers of an image and a region 20 A color image searching method for searching an image in the database based on a color feature of a query image, comprising the step of (a) performing a search based on representative colors of a query image and their ratio in the database indexed by assigning the representative colors of a database image to a color space divided into a plurality of regions 21 The color image searching method according to claim 20, wherein the color space is a three-dimensional color space 22 The color image searching method according to claim 20 wherein the step (a) comprises the steps of (a-1 ) obtaining representative colors of a given query image and their ratio, (a-2) selecting a region corresponding to the representative color obtained in the step (a-1 ) in a color space divided into a plurality of regions, (a-3) selecting a data group indexed into the selected region from a database, and (a-4) identifying matched data in which the difference in the ratio of the representative color f the query image is less than a predetermined threshold value in the selected data group 23 The color image searching method according to claim 22, wherein the step (a) further comprises the steps of (a-5) obtaining the sum of the ratio of same regions from the identified data, and (a-6) determining the region in which the difference between the sum of the obtained ratio and the sum of the ratio to the query image is less than a predetermined threshold value as a searched image 24 The color image searching method according to claim 21 , wherein the step (a) comprises the steps of (a-1 ) obtaining representative colors of a given query image and their ratio, (a-2) selecting a region corresponding to the representative color obtained in the step (a-1 ) in a color space divided into a plurality of regions, (a-3) selecting a data group indexed into the selected region from a database, and (a-4) identifying matched data in which the difference in the ratio of the representative color of the query image is less than a predetermined threshold value in the selected data group 25 The color image searching method according to claim 24, wherein the step (a) further comprises the steps of (a-5) obtaining the sum of the ratio of same regions from the identified data, and (a-6) determining the region in which the difference between the sum of the obtained ratio and the sum of the ratio of the query image is less than a predetermined threshold value as a searched image 26 The color image searching method according to at least one of claim 22 or claim 23, further comprising the step of performing the steps in a color space with respect to neighboring peripheral regions in the case where there are no regions determined as the searched image 27 The color image searching method according to one of claims 20 through 25, wherein the ratio is a percentage 28 The color image searching method according to claim 26, wherein the ratio is a percentage 29 The color image searching method according to at least one of claims 20 through 25 or claim 28, wherein the query image is one region of the image divided into a plurality of regions, and the searched image is one region of the database image divided into a plurality of regions 30 The color image searching method according to claim 26, wherein the query image is one region of the image divided into a plurality of regions, and the searched image is one region of the database image divided into a plurality of regions 31 The color image searching method according to claim 27, wherein the query image is one region of the image divided into a plurality of regions, and the searched image is one region of the database image divided into a plurality of regions 32 A color image searching method for searching an image in the database based on a color feature of a query image, comprising the steps of (a-1 ) obtaining representative colors of given query regions and their ratio, (a-2) selecting a lattice point corresponding to the representative color obtained in the step (a-1 ) in a three-dimensional color space divided into a plurality of lattices, (a-3) selecting a data group corresponding to the selected lattice point from the database in which a region identifier expressing representative colors of data images, their ratio, and serial numbers of an image and a region is stored as data, and (a-4) identifying matched data in which the difference in the ratio of the representative color of the query regions is less than a predetermined threshold value in the selected data group 33 The color image searching method according to claim 32, further comprising the steps of (a-5) obtaining the sum of the ratio of same regions from the identified data, and (a-6) determining the region in which the difference between the sum of the obtained percentage and the sum of the ratio of the query regions is less than a predetermined threshold value as a searched image 34 The color image searching method according to claim 33, further comprising the step of performing the steps in a color space with respect to neighboring peripheral lattice points in the case where there are no regions determined as the searched image 35 A medium for storing a program performing a color image searching method, comprising the steps of: (a-1 ) obtaining representative colors of given query regions and their ratio; (a-2) selecting a lattice point corresponding to the representative 5 color obtained in the step (a-1) in a three-dimensional color space divided into a plurality of lattices; (a-3) selecting a data group corresponding to the selected lattice point from the database in which a region identifier expressing representative colors of data images, their ratio, and serial numbers of an o image and a region is stored as data; and (a-4) identifying matched data in which the difference in the ratio of the representative color of the query regions is less than a predetermined threshold value in the selected data group. 5 36. The medium according to claim 34, wherein the color image searching method further comprises the steps of: (a-5) obtaining the sum of the ratio of same regions from the identified data; and (a-6) determining the region in which the difference between the sum o of the obtained percentage and the sum of the ratio of the query regions is less than a predetermined threshold value as a searched image. 37. The media according to claim 36, wherein the color image searching method further comprises the step of performing the steps in a 5 color space with respect to neighboring peripheral lattice points in the case where there are no regions determined as the searched image.

Inventors: CHOI YANG LIM, DENG YINING, MANJUNATH B S, SHIN HYUN DOO, CHOI, YANG, LIM, DENG, YINING, MANJUNATH, B., S., SHIN, HYUN, DOO
Applicants: SAMSUNG ELECTRONICS CO LTD, UNIV CALIFORNIA, SAMSUNG ELECTRONICS CO., LTD., THE REGENTS OF THE UNIVERSITY OF CALIFORNIA
Application year: 2000
Main classification: H04N9
IPC codes: G06F17, G06T7, H04N1, H04N5, H04N9