A Chromatic Image Analysis for Evaluating Appearance of Agricultural Products Using Color Distribution Entropy

Transcription

1 A Chromatc Image Analyss for Evaluatng Appearance of Agrcultural Products Usng Color Dstrbuton Entropy Kyosuke Yamamoto 1, Takash Togam 2, Atsush Hashmoto 2 Yousuke Yoshoka 3, Sesh Nnomya 1, Takaharu Kameoka 2 * 1 The Unversty of Tokyo, Yayo, Bunkyo, Tokyo, Japan 2 Me Unversty, 1577 Kurma-machyacho, Tsu, Me, Japan 3 Natonal Insttute of Vegetable and Tea Scence, NARC, Ano, Tsu, Me , Japan *Correspondng author. E-mal: kameoka@me-u.ac.jp Abstract Color and shape of fruts are the mportant ndces whch evaluate the qualty of commodtes and varety characterstc. We constructed an mage acquston system usng a combnaton of color hstogram and modfed Color Dstrbuton Entropy (CDE) method to optmze color analyss of agrcultural products. The strawberry frut was used for analyss snce ts color s an mportant ndcator of qualty. Our chromatc mage acquston system enabled capture of strawberry mages under dffuse llumnaton by usng cylndrcal paper as the lght dffusng materal to provde mages wth accurate color nformaton. A standard strawberry wth the standard color, shape, and sze of each cultvar was chosen from the obtaned samples by vsual observaton. Then, smlarty between the standard strawberry mage and the other mages was calculated on the bass of color, shape and sze of strawberry. The expermental result s qute smlar to the vsual observaton. Key words: Strawberry, Color Dstrbuton Entropy, Shape, Image acquston, Smlarty 1. Introducton Color and shape of fruts are the mportant ndces whch evaluate the qualty of commodtes and varety characterstc. Image analyss s a powerful method to solve these problems. Many studes for evaluaton of agrcultural products have been made usng mage analyss. We have been made some researches on standard color and shape of agrcultural products (Motonaga et al., 1998)(Koundou et al., 2002). We used polar and tangental coordnates n shape analyss. It s very mportant that features of mages such as the color structure has to be quanttatvely evaluated n the color mage analyss. One of the possble ways s to use the "Content-based Image Retreval, CBIR". As the CBIR technque, Color Dstrbuton Entropy (CDE) shows color-spatal nformaton n an mage by usng nformaton entropy (Rao et al., 1999). The ams of ths study are to develop a new method for the appearance evaluaton of agrcultural product based on a chromatc mage analyss and to determne the appearance characterstc dstance from the standard strawberry on the bass of color, shape and sze. 2. Expermental Setup and Method 2.1. Expermental Image Acquston System The schematc dagram of our chromatc mage acquston system was shown n Fg.1 (Kmura et al., 2010). It s composed of dgtal sngle lens reflex camera (Nkon D300), fluorescent lamp wth hgh color renderng propertes of 5500K as the llumnant (LS SPIRAL VITALIGHT), dark room wth curtans that cut off all outsde lght, the cylndrcal dffuser (Kent paper, Lumnescent neutral whte), dsplay (Samsung Sync Master XL24) and computer (Apple Mac Pro, 2009/2 model). The lght rradated from standard llumnant nstalled on rght and left hand sde becomes the dffused lght nsde the cylnder by passng the standard cylndrcal dffuser. Then the dffused lght rradates the object set at the cylnder bottom. The camera located above the sample remotely takes the pcture.

2 FIGURE 1: Schematc dagram of mage acquston apparatus 2.2. Materals and Method The strawberry frut was used for analyss snce ts color s an mportant ndcator of qualty. Strawberres of 34 cultvars shown n Table 1 were harvested from January to February n 2010 at the Natonal Insttute of Vegetable and Tea Scence. For these chromatc mages whch were acqured wthn 72 hours from the harvestng, evaluaton was made n the vsual observaton. TABLE 1: Strawberres used n the experment

3 3. Image Analyss 3.1. Color Smlarty by Usng CDE In ths study, as the CBIR technque, color mage analyss usng Color Hstogram and CDE was appled. Fg.2 shows the modfed annular crcle determnaton n CDE (Yamamoto et al., 2011). Snce color-spatal nformaton depends on the sze of object n the exstng CDE technque whch determnes the radus of annular crcle based on the color dstrbuton (Fg.2 (a)), ths study used a radus of annular crcle determned by normalzng the strawberry sze based on the longest dameter of each strawberry so that the color-spatal nformaton becomes ndependent to strawberry sze (Fg.2 (b)). (a) Orgnal CDE FIGURE 2: Annular crcle determnaton (b) Modfed CDE HSV color space used n ths study s unformly quantzed nto 16 levels of hue, 4 levels of saturaton and value gvng a total of 256 Color bns so that the load to the computer was reduced and the evaluaton was made comprehensble (Yamamoto et al., 2010). Gven that h as the color hstogram of Color bn, the smlarty of mages q 1 and q 2 can be obtaned by the followng equaton (1) (Rao et al., 1999). d(q 1,q 2 ) = n =1 q mn(h 1 q,h 2 ) mn(e q 1 q,e 2 ) q max(e 1 q,e 2 ) q q Frst part, mn( h, h gves the hstogram ntersecton whch measures the smlarty between ) two color hstograms. The hstogram ntersecton s common tool whch s obtaned by the sum of smaller color hstogram of each Color bn. That s to say, the hstogram ntersecton shows crossover when two graphs of color hstogram are supermposed. Second part of q q q q equaton (2), mn( E, E ) max( E, E ) measures the smlarty of the spatal dstrbuton of a Color bn Shape Smlarty by Usng Polar and Tangental Coordnates The strawberry shape also has mportant nformaton of ts qualty. Snce we have already developed the method on shape analyss usng r-θ-φ coordnate system (Motonaga et al., 1998), ths shape analyss was appled to strawberry. Shape analyss was performed by the projecton of bnary mage of strawberry on tangent coordnate system. The orgn was set on the center of gravty. A vector from the orgn to a pont on the orbtal was auxlary drawn as an arrow. Let r, θ and φ be vector, angle of the vector and angle between the vector and tangent lne at the pont along the orbtal (Fg.3). Then the orbtal can be projected nto tangent coordnate system wth parameters, θ and φ. Fg.3 shows a shape sgnature of the strawberry not nfluenced by ts sze when θ was plotted n the horzontal axs and φ n the vertcal axs. (1)

4 FIGURE 3: Shape sgnature of strawberry The earth mover s dstance (EMD) can be appled to shape sgnature matchng (Rubner et al., 2000). The soluton s the mnmum amount of work requred to transform one sgnature nto the other. Ths can be formalzed as the followng lnear programmng problem: Let 𝑆 ={(θ, φ ),, (θ, φ )} be the frst shape sgnature wth m clusters, where θ s the cluster representatve and φ s the weght of the cluster; 𝑆 ={(θ, φ ),, (θ, φ )} the second shape sgnature wth n clusters; and D= [dj] the ground dstance matrx where dj s the ground dstance between clusters 𝜃 and 𝜃. We want to fnd a flow F = [ fj], wth fj the flow between 𝜃 and 𝜃, that mnmzes the overall cost. WORK(𝑆, 𝑆, 𝐅) = 𝑑" 𝑓" 𝑓" 0, 1 𝑖 𝑚, 1 𝑗 𝑛 (2) (3) 𝑓" φ, 1 𝑖 𝑚 (4) 𝑓" φ, 1 𝑗 𝑛 (5) 𝑓" = mn ( φ φ ), (6) Gven, under these constrants, the most sutable flow s mn (WORK 𝑆, 𝑆, 𝐅 ), the earth mover s dstance EMD(𝑆, 𝑆 ) s defned as EMD 𝑆, 𝑆 = "# ("#$,,𝐅 ) " (7) In ths work, ths EMD was used to defne the shape smlarty Sze Smlarty As a sze ndex, the area of projected object was used. Let the sze of materal z be 𝐴", the sze of materal zj be 𝐴", sze smlarty S"#$ (z, z ) s defned as S"#$ z, z = " " " " (8) 4. Results and Dscusson The chromatc mage of strawberry surface and cross secton s shown n Fg.4. In the surface mage of strawberry, t was confrmed that surface texture was accurately recorded

5 because the reflecton around the seeds whch gave the adverse effect on color evaluaton dsappeared. On the other hand, n the case of cross secton strawberry mage, the obtaned color was almost equal to the one recognzed under the standard llumnant. (a) Surface Image FIGURE 4: Strawberry mage (b) Cross secton Image In the mage analyss, a cultvar y01 n Table 1 was appled, because y01 has the most samples wth dverse appearance based on the dfferent cultvaton condtons among 34 cultvars harvested for ths study. A strawberry wth standard color, shape and sze of y01 was selected by vsual observaton, and determned to be the standard strawberry of y01 of mage analyss When evaluatng the appearance characterstcs of agrcultural products, t s thought that the expert evaluates each of plural appearance characterstcs ndependently, and then performs a comprehensve evaluaton. Therefore, n ths study, suppose that there are orthogonalty relatons among three appearance characterstcs, the n-dmensonal Eucldean space was proposed as a metrc space of appearance characterstc dstance between objects. FIGURE 5: Appearance characterstc dstance from the standard strawberry

6 Fg.5 shows the result of the analyss on the appearance characterstc dstance from the standard strawberry. As s shown n Fg.5, the tendency of surface smlarty was almost equal to the evaluaton by vsual observaton. Therefore, ths smlarty measure based on the color, shape and sze analyss seems to be effectve for the evaluaton of strawberry appearance. It should be necessary to determne the standard color, shape and sze of each cultvar based on the standard strawberry chosen by the statstcal analyss wth the larger amount of samples, though we selected the standard strawberry whch looks standard n color, shape, and sze among the qute small amount of y01 samples n ths analyss. 5. Concluson Ths paper attempts to construct the strawberry breedng mage database wth color, texture, shape and sze of strawberry. Therefore, we acqured strawberry mage of dfferent cultvars and conducted color analyss of strawberry mages. CDE technque n the CBIR was appled as the color analyss method to evaluate color-spatal nformaton quanttatvely. To use color-spatal and sze nformaton as the ndependent feature, exstng CDE technque was modfed by normalzng the sze of the object. A standard strawberry wth the standard color, shape, and sze of each cultvar was chosen from the obtaned samples by vsual observaton. Then, smlarty between the standard strawberry mage and the other mages was calculated on the bass of color, shape and the sze of strawberry. The expermental result s qute smlar to the vsual observaton. Ths result suggests that mage analyss method of ths study could be effectve for the evaluaton of strawberry appearance. Acknowledgements Ths work was supported by KAKENHI (Grant-n-Ad for Scentfc Research (B) ). We also acknowledge fnancal support from JST for the executon of these studes. Reference lst Kmura, Y., Yamamoto, K., Togam, T., Hashmoto, A., Kameoka, T., & Yoshoka, Y. (2010) Constructon of the prototype system for the chromatc mage analyss usng Color Dstrbuton Entropy, Proceedngs of SICE Annual Conference 2010, Kondou, H., Ktamura, H., Nshkawa, Y., Motonaga, Y., Hashmoto, A., Nakansh, K., & Kameoka, T. (2002). Shape Evaluaton by Dgtal Camera for Grape Leaf, 3rd Asan Conference for Informaton Technology n Agrculrue, Motonaga, Y., Kondou, H., Kameoka, T., & Hashmoto, A. (1998). Determnaton of the Standard Shape and Color of Agrcultural Products, Proceedngs of QCAV'98, Rao, A., Srhar, R.K., & Zhang, Z. (1999). Spatal color hstograms for content-based mage retreval, Tools wth Artfcal Intellgence, Proceedngs of the 11th IEEE Internatonal Conference on, Rubner, Y., Tomas, C., & Gubas, L. J. (2000). The earth mover's dstance as a metrc for mage retreval, Internatonal Journal of Computer Vson, 40(2), Yamamoto, K., Kmura, Y., Togam, T., Hashmoto, A., Kameoka, T., & Yoshoka, Y. (2010) Color mage database constructon for the strawberry breedng, Proceedngs of SICE Annual Conference 2010, Yamamoto, K., Kmura, Y., Togam, T., Yoshoka, Y., Hashmoto, A., & Kameoka, T. (2011). A Chromatc Image Analyss System Usng Content-Based Image Retreval (n Japanese), Agrcultural Informaton Research, 20(4),