Mohammad A. Karim

Color image encryption using double random phase encoding

A new encryption technique is proposed to encrypt color images using existing optical encryption systems for gray-scale images. The color images are converted to their indexed image formats before they are encoded. At the decryption end, the color images are recovered by converting the decrypted indexed images back to their RGB formats. The proposed single-channel color image encryption method is more compact and robust than the multichannels methods. Since color information is added to the shape information, better verification performance can be achieved in optical security systems.xa0©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 21: 318–323, 1999.

Illumination-invariant pattern recognition with joint-transform-correlator-based morphological correlation.

The performance of nonlinear morphological correlation is investigated and compared with that of conventional linear correlation. In particular, the effects of illumination variations on the morphological correlation output are investigated in detail. The morphological correlation is shown to be invariant to uniform input-image illumination when the input-image illumination is higher than that of the reference. It also provides higher pattern discriminability, sharper peaks, and more-robust detection in the presence of salt-and-pepper noise than does the linear correlation. Computer-simulation results are provided.

Super-resolution enhancement technique for low resolution video

Super-resolution enhancement is the technique of increasing spatial resolution of an image from the image itself or from several noisy images of the same scene but with additional information such as motion. This paper presents a kernel regression approach to reconstruct a high resolution image from several low resolution video frames. In many applications including cell phone and webcam the imaging sensors capture low resolution images due to low cost sensors or physical limitation of the hardware. So, the proposed resolution enhancement technique could be used as an inexpensive software alternative. The performance of the proposed algorithm is evaluated with several grayscale and color video streams and found successful when compared to other state of the art techniques.

Traffic shaping for MPEG video transmission over the next generation internet

The Internet Engineering Task Force (IETF) has proposed the Guaranteed Service (GS) in the Integrated Services model with firm delay and bandwidth guarantees. In this paper, we study the effects of a token bucket traffic shaper at the source on the transmission characteristics of Motion Picture Experts Group (MPEG) compressed video streams over the GS. We develop an analytical model of the traffic shaper, and also carry out numerical simulation of the transmission performance using MPEG trace data from several different video sequences. The analytical model and the numerical simulation results are in excellent agreement. Our study provides a technique to determine the token bucket parameters that have to be specified while setting up a GS flow. Our study reveals that the traffic shaping process gives an end application a wide range of flexibility in controlling the delay. By choosing appropriate token bucket traffic shaper parameters, delay can be reduced significantly without the need to reserve costly network resources for less delay-sensitive applications, while time-critical applications may specify the required token bucket parameters for minimum delay.

High-security optical integrated stream ciphers

We propose a new optical stream cipher for security applica- tions. The stream ciphers security is enhanced using hybrid cellular au- tomata to replace uniform cellular automata as the keystream genera- tors. The encoded ciphertext is obtained by randomly encoding both the initial states of cellular automata and their evolution rules. This results in an increase in complexity to crack the keystream generator and, thus, enhances the security of stream ciphers. The hardware implementation can be also correspondingly reduced. An optical solid-integrated scheme is suggested to implement the proposed stream cipher for high-speed encryption and decryption.

Modification of standard image compression methods for correlation-based pattern recognition

Standard image compression algorithms may not perform well in compressing images for pattern recognition applications, since they aim at retaining image fidelity in terms of perceptual quality rather than preserving spectrally significant information for pattern recognition. New compression algorithms for pattern recognition are therefore investigated, which are based on the modification of the standard compression algorithms to simultaneously achieve higher compression ratio and improved pattern recognition performance. This is done by emphasizing middle and high frequencies and discarding low frequencies according to a new distortion measure for compression. The operations of denoising, edge enhancement, and compression can be integrated in the same encoding process in the proposed compression algorithms. Simulation results show the effectiveness of the proposed compression algorithms.

An analytical approximation for the excess noise factor of avalanche photodiodes with dead space

Approximate analytical expressions are derived for the mean gain and the excess noise factor of avalanche photodiodes including the effect of dead space. The analysis is based on undertaking a characteristic-equation approach to obtain an approximate analytical solution to the existing system of recurrence equations which characterize the statistics of the random multiplication gain. The analytical expressions for the excess noise factor and the mean gain are shown to be in good agreement with the exact results obtained from numerical solutions of the recurrence equations for values of the dead space reaching up to 20% of the width of the multiplication region.

High-Speed Image Registration Algorithm with Subpixel Accuracy

A new, fast and computationally efficient lateral subpixel shift registration algorithm is presented. It is limited to register images that differ by small subpixel shifts otherwise its performance degrades. This algorithm significantly improves the performance of the single-step discrete Fourier transform approach proposed by Guizar-Sicairos and can be applied efficiently on large dimension images. It reduces the dimension of Fourier transform of the cross correlation matrix and reduces the discrete Fourier transform (DFT) matrix multiplications to speed up the registration process. Simulations show that our algorithm reduces computation time and memory requirements without sacricing the accuracy associated with the usual FFT approach accuracy.

Programmable modified-signed-digit addition module based on binary logic gates

A new binary logic based modified-signed-digit (MSD) adder is proposed. By encoding MSD digits in pairs of binary bits, each of the four MSD transforms can be represented by two cascaded binary logic operations. This leads to the design of a compact and integrated pro- grammable MSD addition module. The three operation steps in the MSD addition can be realized using this same module simply by programming the decoding masks.

Automatic target tracking for unmanned aerial vehicle video annotation

This paper describes a system for tracking objects in a video stream obtained from a moving airborne platform. The system is applied to annotate video objects automatically. The object to annotate is indicated by a mouse click. The proposed tracking algorithm is based on the general framework of spatiotemporal segmentation followed by temporal tracking. However, it differs from existing techniques in the following features. The same algorithm is used in tracking both moving and stationary objects by making the stationary objects move. It is general enough to handle objects of various types and sizes, including point objects. The system has a fast implementation because all image operations are applied to small image regions only. We demonstrate the effectiveness of the proposed algorithm on a few real video sequences.