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Image registration using n-fold dihedral blur removal
- 1. IMAGE REGISTRATION USING N-FOLDBLUR REMOVAL
- 2. CONTENTS • Introduction • Objective •Existing system • Proposed system • Block diagram • Formulae • Output 1
- 3. INTRODUCTION • The originalmethod works for unknown blurs, assuming the blurring point-spread function(PSF) exhibits an N-fold rotational symmetry. • This makes registration algorithm well-suited in applications where blurred image registration must be used as a preprocess step. • This leads to an improvement of the image registration performance. 2
- 4. OBJECTIVE • To improvethe performance of image registration and reduce the error occurrence, we implement the N-fold blur removal. 3
- 5. EXISTING SYSTEM S.no TitleAlgorithm Drawback Performance 1. Automatic image registration for applications in remote sensing Edge-based Selection of the control points Feature inconsistance Accuracy is 76.5% 2. Blur invariant translational image registration for N- fold symmetric blurs Global based blur invariant PSF has no symmetry Computational speed is 170 seconds 3. Combined invariants to similarity transformation and to blur using orthogonal zernike moments Orthogonal zernike moments Not adaptive for order invariance(on ly even order invariance) Accuracy 92% 4
- 6. Cond… S.no Title AlgorithmDrawback Performance 4. Moment forms invariant to rotation and blur in arbitrary number of dimensions Moment forms invariant Degraded performance of boundary effect Accuracy 83% 5. Blur Invariant Phase Correlation in X-Ray Digital Subtraction Angiography spline image warping Not support for motion artifacts Registration error is 0.9 6. Multichannel blind deconvolution of spatially misaligned images Maximum a posteriori probability (MAP) Inaccurate registration of channels Better performance and high SNR 5
- 7. Cond… S.no Title AlgorithmDrawback Performance 7. Wavelet-domain blur invariants for image analysis Spatial- Domain Blur Invariants(SD BI) Failed in asymmetric blur registration task Accuracy is 75% 8. Degraded image analysis: An invariant approach Combined invariants Focused only on combined invariants not on image rotation and affine transform. SNR value is lower than 10 db 6
- 8. PROPOSED SYSTEM • Registrationmethod designed specifically for registering blurred images. • Registration of blurred images requires special methods because general registration methods usually do not perform well on blurred images. • Global based blur invariant approach of phase correlation. 7
- 9. BLOCK DIAGRAM 8 Image Blurredimage PSF estimation N-fold blur removal (3-fold and 6-fold) Deblurred image
- 10. Image taken withcamera having shutter with four blades and shape of the PSF can be clearly viewed in the out-of-focus background. PSF has 4-fold rotational symmetry 9
- 11. Reference image Blurredsensed image 10
- 12.
- 13. Registration of twoimages 12
- 14. formulae Recalling the originalmethod g⟹ blurred sensed image f⟹ reference image h⟹ point spread function Δ⟹ shift x⟹ number of pixels h⟹ h(r,θ) = h(r, θ+2πj/N) N⟹ number of folds 14 g(x) = (f * h)(x - Δ)
- 15. Cond… Projection operators ⟹Used toeliminate the blur 𝐾𝑗 (𝑓) (𝐮) = F(u) / F(𝑅𝑗u) ; j=1,………,N F(u) ≝ F{f}(u) is the Fourier transform of f(x) Rju⟹ Rotation of frequency coordinates by the angle 2πj/N Rju= 2*pi*j/N 15
- 16. Cond… Blur Invariant Operators ⟹To calculate reflection operator S(x) = cos 2𝛼 sin 2𝛼 sin 2𝛼 − cos 2𝛼 𝑥 𝑦 S(x)⟹ Reflection operator 𝛼 ⟹ Angle b/w reflection line and horizontal axis 16
- 17. Cond… ⟹ To calculatethe Fourier Transform for original image and dihedral blurred image f ⟹Original image Df ⟹Dihedral blurred image 17 F{f} / F{Df}
- 18. Cond… ⟹ To calculatethe invariants to dihedral blur 𝐾𝑗 = F{f} / F{𝑅𝑗 𝑓} ; j=1,………,N F{f} ⟹ Fourier transform of original image F{𝑅𝑗 𝑓} ⟹ Rotational symmetry(Cyclic groups,Cf) L𝑗 = F{f} / F{𝑅𝑗S𝑓} ; j=1,………,N F{𝑅𝑗S𝑓} ⟹ Rotational and Reflectional symmetry (Dihedral groups, Df) 18
- 19. Cond… Image registration algorithm ⟹usedto design a robust blur-invariant registration method To calculate the normalized cross-power spectra Cj = 𝑘𝑗 (𝑓) 𝑘𝑗 g ∗ ; j=1,…N (Rotation) │ 𝑘𝑗 (𝑓) 𝑘𝑗 g │ Bj = 𝐿𝑗 (𝑓) 𝐿𝑗 g ∗ │ 𝐿𝑗 (𝑓) 𝐿𝑗 g │ ; j=1,…N (Rot+Ref) 19
- 20. Cond… Inverse Fourier Transformof Cj f −1 {Cj }(x) = 𝛿(x +Δ - 𝑅 𝑁−𝑗 Δ) Inverse Fourier Transform of Bj f −1 {Bj }(x) = 𝛿(x +Δ - S𝑅 𝑁−𝑗 Δ) 20
- 21. Two images acquiredby a hand-held camera with different focus settings and shift 21
- 22. Two frames froma video sequence taken with different focus settings 22
- 23.
- 24.
- 25. Rgb to grayconverted image 25
- 26. Psf for Dihedralblurred image 26
- 27.
- 28. Psf for blurredimage 28
- 29. Registration of 3-foldand 6-fold 29
- 30. Performance N-Folds Mis-Registration (%) MSEPSNR (dB) Only fold Fold+ dihedral 3-Folds 31% 20% 0.005 33 dB 6-Folds 22.5% 12% 0.0019 38.5 dB 30
- 31.
Editor's Notes
- #2 Image registration is the process of aligning two or more images of the same scene. N-fold means number of folds. The formula for N-fold is no of points/2
- #3 Blur can be originated from camera shake, wrong focus, scene motion, atmospheric turbulence, sensor imperfection, low sampling density etc.
- #4 Blur is the relative motion between camera and scene. Point spread function(PSF) is the representation of an image. Point spread function consists of rotational and reflection symmetry. PSF describes the response of an imaging system to point object.
- #5 The main objective of this project is to improve the performance of image registration and reduce the error occurrence by implementing N-fold blur removal.
- #9 The special registration methods used are Global based blur invariant registration method.
- #11 Rotational symmetry means an object that looks same after a certain amount of rotation.
- #15 The original method works for unknown blurred image.
- #20 The main idea is that we may consider the invariants to be Fourier transforms of hypothetical non-blurred images, which can be registered by phase correlation.