Fig. 1. Morphologies of LDMed TA15 titanium alloy. (a) Macroscopic; (b) microscopic

Fig. 2. Decomposition and reconstruction process of DWT

Fig. 3. Original defects. (a) C-scan image; (b) 3D gray image

Fig. 4. Decomposition coefficients of DWT at level 3. (a) Low-frequency coefficients; (b) horizontal high-frequency coefficients; (c) vertical high-frequency coefficients; (d) diagonal high-frequency coefficients

Fig. 5. Flow chart of image processing algorithm

Fig. 6. Wavelet coefficients after Gamma transform. (a) Low-frequency coefficients; (b) horizontal high-frequency coefficients; (c) vertical high-frequency coefficients; (d) diagonal high-frequency coefficients

Fig. 7. Reconstructed image of DWT. (a) 2D image; (b) 3D image

Fig. 8. Comparison among results by various algorithms

Fig. 9. Comparison among processing results. (a) Ultrasonic detection image of defects; (b) enhancement image by proposed algorithm; (c) sectional metallograph