METHOD OF DETECTING SPATIAL GRADIENT BY UTILIZING COLOR INFORMATION

Abstract: The present invention provides a method of detecting spatial gradient which is applied to an image region segmentation and boundary extraction system comprising a first step of simplifying each color information of an image signal; a second step of detecting said spatial gradient information for each simplified color information; a third step of multiplying an appropriate weighting value to each color gradient information; and a fourth step of obtaining a combined spatial gradient for each weighted color gradient information.

Description: METHOD OF DETECTING SPATIAL GRADIENT BY UTILIZING COLOR INFORMATION BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a method of detecting spatial gradients which are used in watershed algorithms which partitions an image into semantic regions with precise boundaries by utilizing color information. Information Disclosure Statement Conventional methods of detecting spatial gradient have detected spatial gradients by using a morphological gradient operator for brightness information. Since the conventional methods only use the brightness information, it is difficult to obtain the precise spatial gradients in between regions having similar brightness although the two regions are different. Therefore, in case of applying the conventional methods of detecting spatial gradients to the watershed algorithms, there is a problem that the region segmentation or boundary detection for objects in an image can not be satisfactorily performed. SUMMARY OF THE INVENTION The present invention invented to solve the problems described above has an object that it provides a method of detecting spatial gradient which detects visually meaningful spatial gradient by using color information to perform the precise region segmentation and boundary extraction by using the spatial gradient to the watershed algorithm. The present invention to accomplish the object described above provides a method of detecting spatial gradient which is applied to an image region segmentation and boundary extraction system, the method being characterized in that it comprises a first step of simplifying each color information of an image signal; a second step of detecting said spatial gradient information for each simplified color information; a third step of multiplying an appropriate weighting value to each color gradient information; and a fourth step of obtaining a combined spatial gradient for each weighted color gradient information. BRIEF DESCRIPTION OF THE DRAWINGS For fuller understanding of the nature and object of the invention, reference should be had to the following detailed description taken in conjunction with the accompanying drawings in which: Fig. ' 1 is a constructional block diagram of the image region segmentation and boundary extraction system to which the present invention is applied; and Fig. 2 is a flowchart of the method of detecting spatial gradient acording to the present invention. Similar reference characters refer to similar parts in the several views of the drawings. DETAILED DESCRIPTION OF THE INVENTION Below is given a detailed description of an embodiment according to the present invention with reference to the accompanying drawings. Fig. 1 shows a constructional block diagram of an image region segmentation and boundary extraction system to which the present invention is applied, wherein reference numeral 101 denotes an image simplifier, 102 denotes a spatial gradient detector, and 103 denotes a watershed algorithm. First, the image simplifier 101 simplifies an input signal image to be adapted to the region segmentation and boundary information extraction. That is, the image simplifier 101 removes unwanted details from the image by using an appropriate filter, i.e. it removes small changes which are of no help to detect meaningful boundary extraction. The spatial gradient detector 102 detects a spatial gradient representing a boundary information of a region from the simplified image received from the image simplifier 101. At this time, the information of spatial gradient is obtained by using a morphological gradient operator. Next, the spatial gradients obtained by the Spatial Gradient Detector 102 are used as input to the watershed algorithm 103 for region detection. Fig. 2 is a flowchart of a method of detecting a spatial gradient according to the present invention. Informations of image signal are composed of arbitrary color elements including red, green and blue. In the present invention, the spatial gradient information is detected by using not only the brightness information but also all the three elements of color image signal to perform the visually meaningful inage segmentation and boundary information by applying the spatial gradient information to the watershed algorithm. First, the image is simplified at step 201 so that the image segmentation is easy by using an appropriate filter to each of the three elements (red or brightness signal, blue or the first chrominance difference signal, and green or the second chrominance difference signal) of the color image signal. That is, Rs, Gs and Bs are obtained by simplifying the interior of region while reserving the boundary of region. Here, the three elements of color image signal used as input signal may be any color coordinate system including red, green and blue. At this time, in simplifying the image, the first chrominance difference signal is the brightness minus red and the second chrominance difference signal is the brightness minus blus. Thereafter, the spatial gradients for the simplified three color information are obtained at step 202. That is, each of the spatial gradient information G Rs , G Gs and G Bs is obtained by applying the morphological gradient operator. Next, appropriate weighting values are multiplied to the three color gradient informations obtained by using the morghological gradient operator depending upon the importance of the three color gradient informations at step 203. That is, each of α G Rs , β G Gs and γG Bs is obtained. In this way, the maximum values of three color gradients informations multiplied by the arbitrary weighting values are obtained for each pixel at step 204. That is, the combined spatial gradients are obtained by obtaining the maximum values of G Rs , β G Gs and γG Bs . The maximum gradients thus obtained are defined as the spatial gradients of that pixel. If the watershed algorithm is applied to the spatial gradients, the precise region segmentation and boundary extraction are possible. The present invention described above has effects that the detection of the visually meaningful spatial gradients is possible by obtaining the spatial gradients by using the color information, and the precise image region segmentation and boundary information extraction is possible by applying the watershed algorithm to the spatial gradients. The foregoing description, although described in its preferred embodiment with a certain degree of particulaity, is only illustrative of the principles of the present invention. It is to be understood that the present invention is not to be limited to the preferred embodiments disclosed and illustrated herein. Accordingly, all expedient variations that may be made within the scope and the spirit of the present invention are to be encompassed as further embodiments of the present invention.

Claims: What is claimed is: 1. A method of detecting spatial gradient which is applied to an image region segmentation and boundary extraction system comprising the steps of: a first step of simplifying each color information of an image signal; a second step of detecting said spatial gradient information for each simplified color information; a third step of multiplying an appropriate weighting value to each color gradient information; and a fourth step of obtaining a combined spatial gradient for each weighted color gradient information. 2. The method as claimed in claim 1, wherein said third step of multiplying an appropriate weighting value multiplies said appropriate weighting value depending upon the importance of each color gradient information. 3. The method as claimed in claim 1 or 2, wherein said fourth step of obtaining a combined spatial gradient obtains said combined spatial gradient by obtaining maximum value of each color gradient information. 4. The method as claimed in claim 3, wherein said each color image signal comprises color components in any color coordination systems including red, green and blue.

Inventors: CHOI JAE GARK, KIM MUN CHURL, LEE MYOUNG HO, CHOI, JAE, GARK, KIM, MUN, CHURL, LEE, MYOUNG, HO
Applicants: CHOI JAE GARK, KIM MUN CHURL, KOREA ELECTRONICS TELECOMM, LEE MYOUNG HO, CHOI, JAE, GARK, ELECTRONICS AND TELECOMMUNICATIONS RESEARCH INSTITUTE, KIM, MUN, CHURL, LEE, MYOUNG, HO
Application year: 1998
Main classification: G06T
IPC codes: G06T5, G06T7, H04N9