Segregation of images is a critical step in processing images, computer vision, and a variety of other disciplines. The technique involves decomposing an illustration into numerous components or components, every single one that consists of an ensemble of elements with identical features for example African descent, frequency, or consistency. The most important objective of appearance, the intention of fragmentation seems to reduce complexity or customize the mathematical representation of an illustration in a way that is more readily reasonable and more straightforward for assessment. It is widely employed to locate boundaries and features in photos, and this is favorable in an assortment of industries including clinical imaging, object detection, recognition, and autonomous vehicles. Several image segmentation techniques are available, and in incorporating thresholding, zone is an area-based differentiation and corner-based recognition. A threshold segment is a simple and commonly used technique that involves setting a threshold value and dividing the pixels into two classes based on their intensity values. Region-based segmentation involves grouping pixels based on their spatial proximity and similarity in characteristics, while edge-based segmentation involves detecting edges or boundaries in an image and using them to separate different regions.

Twin decomposition, consisting of equal and random modulus decompositions, not only makes a cryptosystem asymmetric but also resists special attack. A new double-image asymmetric cryptosystem using twin decomposition in fractional Hartley domain is proposed. An input grayscale image, bonded with another grayscale image as its phase mask, is transformed via fractional Hartley transform. Equal modulus decomposition is applied on the resulting image, giving us two intermediate images. One of them is subjected to another fractional Hartley transform followed by random modulus decomposition, whereas the other serves as the first private key. The application of random modulus decomposition also results in two images: encrypted image and the second private key. During the process of decryption, firstly the encrypted image is combined with second private key and thereafter it is subjected to inverse fractional Hartley transform. The resulting image is then combined with the first private key, and followed by another inverse fractional Hartley transform, thus recovering the two original images. The proposed cryptosystem is validated for pairs of grayscale images.

An asymmetric single-channel color-image cryptosystem is presented that uses singular value decomposition and Tinkerbell map in the fractional Fourier domain. The input image is split into red, green, and blue channels. The red component is used as plaintext, and green and blue components are used as phase masks in the cryptosystem. MATLAB is used for computations of results presented in this paper. The proposed cryptosystem is validated for color images of size 256 × 256 × 3 pixels. The analysis of the attacks establishes the scheme’s resistance to occlusion and noise attack, and the key-space is big enough to endure a brute-force attack. The analysis based on the correlation distribution of neighboring pixels, along with statistical analysis has been performed to examine the efficacy of the cryptosystem. The results indicated high levels of security possessed by the proposed encryption scheme.

Motivated by recent research on asymmetric cryptosystems, a novel asymmetric scheme for image encryption that uses double random-decomposition technique in the fractional Fourier transform domain is proposed. The scheme endures the Special Attack as against conventional asymmetric cryptosystems based on phase-truncated Fourier transform (PTFT), and equal modulus decomposition. In the proposed scheme, an input image is bonded with a random phase mask and then it is subjected to a fractional Fourier transform. The resulting image is decomposed into two components using the random-decomposition technique. One of them will act as the first private key and the other component is subjected to the second fractional Fourier transform followed by another random-decomposition. Again, two new components are obtained, one will act as the second private key and the other is phase-truncated before subjecting it to LU decomposition followed by affine transform to get the encrypted image. The new scheme possesses enlarged key-space consisting of private keys obtained from random-decomposition, orders of fractional Fourier transform, affine transform parameters and permutation matrix of LU decomposition, thereby having a much greater capability to resist brute force attack. A sensitivity analysis has been carried out with respect to the encryption parameters. In addition to its resistance to the Special Attack, the scheme is immune to the basic attacks such as known-plaintext attack, chosen-plaintext attack, ciphertext-only attack, by virtue of its asymmetric nature. The above analysis along with statistical analysis through 3D plots and correlation distribution establish the strength of the proposed cryptosystem.

Motivated by the endurance of phase truncated asymmetric optical cryptosystems against basic attacks, single-channel encryption technique for a color image is proposed, that uses singular value decomposition, and affine transform in gyrator domain. Color 8 images have been used to validate the scheme. The input color image is split into its indexed components-RGB (red, green and blue). The red component of the input image is used as plaintext, and the other two components are used as phase in the encryption scheme. Experimental results presented in the paper are based on computation on MATLAB. The results show that the scheme endures occlusion and noise attacks. The simulation also confirmed the scheme’s sensitivity to the encryption parameters of affine transform and gyrator transform. The overall results show that the proposed encryption scheme exhibits high levels of security.

An asymmetric cryptosystem for phase images is proposed which uses amplitude and phase truncation operators in fractional Fourier domain. LU decomposition and Arnold transform are applied to further strengthen the cryptosystem. Analysis of 3D plots, histograms, and correlation distribution reveals that scheme resist the statistical attacks. Basic attacks like chosen plaintext, known plaintext, ciphertext only etc., are endured by virtue of asymmetric nature of cryptosystem. Well-known noise attack is also performed on the scheme. Results indicate that scheme can tolerate the significant noise and reveal information about the input images. Results also show the scheme sensitivity towards the encrypted parameters like orders of fractional Fourier transform and Arnold transform parameter.