An interactive flower image recognition system

Multimed Tools Appl (2011) 53:53–73 572.1 Flower region segmentationIn order to extract the flower boundary as correctly as possible, the proposed systemprovides a simple interactive interface which allows the user to select the interested flowerfor recognition. Figure 2 illustrates the steps of the interactive flower region segmentationphase. First, the user can draw a rectangular window which circumscribes the interestedflower by using mouse click and drag operations. Let P 0 denote the center point of therectangular window, P 1 , P 2 , P 3 , and P 4 denote the middle points on each of the fourboundary lines of the rectangular window as shown in Fig. 3. For each scan line startingfrom any P i (i=1,2,3,4)toP 0 , the edge point locating at the flower boundary will bedetected. These four edge points will then be regarded as the starting/ending points forboundary tracing. Since the proposed flower edge detection method used the “local cost”value associated with every pixel on each scan line, we will define the local cost first.2.1.1 Definition of local costThe local cost (LC) of a pixel on a scan line is defined as follows:LC ¼ 1 þ MG G; ð1Þwhere G denotes the gradient magnitude for the pixel and MG denotes the maximumgradient magnitude of all pixels in the image. According to the definition of local cost, wecan see that a pixel with strong edge gradient will have a small local cost. In this paper, theSobel operators (see Fig. 4) are employed to compute the horizontal and vertical gradientmagnitudes of a pixel. Let I R (x, y), I G (x, y), and I B (x, y) denote respectively the R, G, and Bcolor values of a pixel locating at (x, y). For R color value, the corresponding gradientmagnitude, notated G R (x, y), is defined as follows:G R ðx; yÞ ¼qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiG 2 R;H ðx;yÞþG2R;V ðx;yÞ; ð2Þwhere G R,H (x, y) and G R,V (x, y) denote respectively the horizontal and vertical gradientsderived by convolving the horizontal and vertical Sobel operators with the 3×3 imageblocks centered at (x, y) and can be described by the following equations:G R;H ðx; yÞ ¼ ½I R ðx þ 1; y 1Þþ2I R ðx þ 1; yÞþI R ðx þ 1; y þ 1ÞŠ½I R ðx 1; y 1Þþ2I R ðx 1; yÞþI R ðx 1; y þ 1ÞŠ ð3ÞFig. 2 Block diagram for flower region segmentation