A novel framework for real-time diseased coral reef image classification

Abstract

The new challenge in image processing is in processing submarine coral reef images. The coral reef disease classification from such submarine coral reef images has become an important research activity that helps marine biologist. An automated system is required to extract texture features so as to classify coral reef diseases from captured images. The proposed framework encompasses an efficient feature descriptor that classifies different submarine images of coral reef with diseases. The proposed framework employs most excellent image processing and machine learning techniques for classification. At first, the diseased coral reef images are segmented using Gradient-based sobel operator. Then, texture features are extracted from HSV color space using the proposed Mean Direct Code Pattern (MDCP) and from RGB space using proposed Diagonal Direction Value Pattern (DDVP). The proposed feature descriptors provide codes considering elements in diagonal directions. The resultant feature vector is then given as input to various classifiers to classify the diseased images. The efficiency of the proposed framework is demonstrated using real-time coral reef diseased images. The performance of various classifiers such as Decision Tree (DT), Classification And Regression Tree (CART), C4.5, Adaboost, Rotation Forest (RoF), Random Forest (RF), SVM, KNN, CNN, PCCNN and Naive Bayes is analysed. Performance results of the proposed framework for diseased coral reef image classification show that the framework outperforms recent works where feature descriptors such as LBP, LDP, CLBP, ILDP, DLBP, LTxXORP, CS-LBP, RLTP, Z ⊕ TZLBP, OC-LBP, LTrP and PRI-CoLBP are used. Classification results are validated by marine biologists.

Appendix 1: To calculate the feature extraction using the proposed method do the following: Consider a 3 × 3 Block B k in image I as shown below

Step 1: Calculate the diagonal directional difference between four directions, namely 45^°, 135^°, 225^° and 315^°on three channels, namely red, green and blue as shown in Eqs. (4)–(12).

Step 2: Calculate the diagonal direction difference between three channels along 45^°, in the following combinations, namely RG, RB, GR, GB, BG, BR as shown in Eqs. (4)–(12).

Step 3: Calculate the diagonal direction difference between three channels along 135^°, in the following combinations, namely RG, RB, GR, GB, BG, BR as shown in Eqs. (4)–(12).

Step 4: Calculate the diagonal direction difference between three channels along 225^°, in the following combinations, namely RG, RB, GR, GB, BG, BR as shown in Eqs. (4)–(12).

Step 5: Calculate the diagonal direction difference between three channels along 315^°, in the following combinations, namely RG, RB, GR, GB, BG, BR as shown in Eqs. (4)–(12).

Step 6: Vector Generation using four diagonal directions in the three planes is as shown in Eqs. (13)–(15).

For 45^°

$$ {\mathrm{R}}_{45^{{}^{\circ}}}=\left\langle 8,7,-7\right\rangle $$

$$ {\mathrm{G}}_{45^{{}^{\circ}}}=\left\langle -11,3,4\right\rangle $$

$$ {\mathrm{B}}_{45^{{}^{\circ}}}=\left\langle 4,5,-10\right\rangle $$

For 135^°

$$ {\mathrm{R}}_{135^{{}^{\circ}}}=\left\langle 10,7,6\right\rangle $$

$$ {\mathrm{G}}_{135^{{}^{\circ}}}=\left\langle 3,3,6\right\rangle $$

$$ {\mathrm{B}}_{135^{{}^{\circ}}}=\left\langle 3,7,4\right\rangle $$

For 225^°

$$ {\mathrm{R}}_{225^{{}^{\circ}}}=\left\langle 5,3,4\right\rangle $$

$$ {\mathrm{G}}_{225^{{}^{\circ}}}=\left\langle -1,0,1\right\rangle $$

$$ {\mathrm{B}}_{225^{{}^{\circ}}}=\left\langle 1,2,0\right\rangle $$

For 315^°

$$ {\mathrm{R}}_{315^{{}^{\circ}}}=\left\langle 6,10,11\right\rangle $$

$$ {\mathrm{G}}_{315^{{}^{\circ}}}=\left\langle 6,7,2\right\rangle $$

$$ {\mathrm{B}}_{315^{{}^{\circ}}}=\left\langle 8,3,7\right\rangle $$

Step 7: Binary Codes Assignment is as shown in Eqs. (16)–(18)

For 45^°

$$ \mathrm{BC}{\mathrm{R}}_{45^{{}^{\circ}}}=\left\langle 1,1,0\right\rangle $$

$$ {\mathrm{BCG}}_{45^{{}^{\circ}}}=\left\langle 0,1,1\right\rangle $$

$$ {\mathrm{BCB}}_{45^{{}^{\circ}}}=\left\langle 1,1,0\right\rangle $$

For 135^°

$$ {\mathrm{BCR}}_{135^{{}^{\circ}}}=\left\langle 1,1,1\right\rangle $$

$$ {\mathrm{BCG}}_{135^{{}^{\circ}}}=\left\langle 1,1,1\right\rangle $$

$$ {\mathrm{BCB}}_{135^{{}^{\circ}}}=\left\langle 1,1,1\right\rangle $$

For 225^°

$$ {\mathrm{BCR}}_{225^{{}^{\circ}}}=\left\langle 1,1,1\right\rangle $$

$$ {\mathrm{BCG}}_{225^{{}^{\circ}}}=\left\langle 0,1,1\right\rangle $$

$$ {\mathrm{BCB}}_{225^{{}^{\circ}}}=\left\langle 1,1,0\right\rangle $$

For 315^°

$$ {\mathrm{BCR}}_{315^{{}^{\circ}}}=\left\langle 1,1,1\right\rangle $$

$$ {\mathrm{BCG}}_{315^{{}^{\circ}}}=\left\langle 1,1,1\right\rangle $$

$$ {\mathrm{BCB}}_{315^{{}^{\circ}}}=\left\langle 1,1,1\right\rangle $$

Step 8: Diagonal Direction Value Assignment is as shown in Eqs. (19)–(21).

For 45^°

$$ \mathrm{DDV}\_\mathrm{BC}{\mathrm{R}}_{45^{{}^{\circ}}}=\left\langle 7\right\rangle $$

$$ \mathrm{DDV}\_{\mathrm{BCG}}_{45^{{}^{\circ}}}=\left\langle 4\right\rangle $$

$$ \mathrm{DDV}\_{\mathrm{BCB}}_{45^{{}^{\circ}}}=\left\langle 7\right\rangle $$

For 135^°

$$ \mathrm{DDV}\_{\mathrm{BCR}}_{135^{{}^{\circ}}}=\left\langle 8\right\rangle $$

$$ \mathrm{DDV}\_{\mathrm{BCG}}_{135^{{}^{\circ}}}=\left\langle 8\right\rangle $$

$$ \mathrm{DDV}\_{\mathrm{BCB}}_{135^{{}^{\circ}}}=\left\langle 8\right\rangle $$

For 225^°

$$ \mathrm{DDV}\_{\mathrm{BCR}}_{225^{{}^{\circ}}}=\left\langle 8\right\rangle $$

$$ \mathrm{DDV}\_{\mathrm{BCG}}_{225^{{}^{\circ}}}=\left\langle 4\right\rangle $$

$$ \mathrm{DDV}\_{\mathrm{BCB}}_{225^{{}^{\circ}}}=\left\langle 7\right\rangle $$

For 315^°

$$ \mathrm{DDV}\_{\mathrm{BCR}}_{315^{{}^{\circ}}}=\left\langle 8\right\rangle $$

$$ \mathrm{DDV}\_{\mathrm{BCG}}_{315^{{}^{\circ}}}=\left\langle 8\right\rangle $$

$$ \mathrm{DDV}\_{\mathrm{BCB}}_{315^{{}^{\circ}}}=\left\langle 8\right\rangle $$

Step 9: Summed Diagonal Direction Value is as shown in Eq. (22).

$$ {\mathrm{SDDV}}_{45^{{}^{\circ}}}=18 $$

$$ {\mathrm{SDDV}}_{135^{{}^{\circ}}}=24 $$

$$ {\mathrm{SDDV}}_{225^{{}^{\circ}}}=19 $$

$$ {\mathrm{SDDV}}_{315^{{}^{\circ}}}=24 $$

Finally feature vector for DDVP is estimated as follows SDDV = < 18, 24, 19, 24>

Step 10: Given image I is converted from RGB to HSV color space

Step 11: Mean Estimation for three planes

As shown in Eq. (26) HMean is estimated for H-Plane, HMean = 5

As shown in Eq. (27) SMean is estimated for S-Plane, SMean = 10

As shown in Eq. (28) VMean is estimated for V-Plane, VMean = 9

Step 12: Diagonal Neighbors Estimation, As shown in Fig. 11, Diagonal neighbors are chosen for comparing with the Mean Value in three planes.

Step 13: Assigning Direct Code, As shown in Eqs. (29) to (31), Direct codes are assigned for three planes.

Step 14: Summed Direct Code, After comparison of diagonal elements with neighbors. Depending on the binary values 0, 1 the codes are assigned. For this 3 × 3 Block B_k, the feature vector is estimated in three planes and summed together as shown in Eq. (35).

Step 15: After Normalization as shown in Eq. (36), SDDC = 16

Step 16: Feature Vector Concatenation as shown in Eq. (37)

Feature Vector (I) = <18, 24, 19, 24, 16>