This paper presents a new technique for contrast enhancement for color images called histogram shifting with alpha rooting. The novelty in the presented method consists in adapting spatial domain techniques into the transform domain. The benefits of operating in the transform domain include low complexity of computations, ease of viewing, and manipulation of the frequency composition of the image and preservation of the phase information. The combination of the alpha-rooting algorithm, coupled with histogram shifting shows the method's effectiveness for enhancing overexposed images. The contrast enhancement parameter of the algorithm is established automatically based on the entropy of the images. A comprehensive comparative study on image-enhancement algorithms based on discrete cosine transform coefficients is provided. Computer simulations and analysis are provided to compare the enhancement performance of the proposed technique to state of the art approaches. We perform a statistical analysis on the results and quantitatively show that the proposed approach performs well for color image enhancement, which is also validated by ratings from human observers.
This paper presents a color image enhancement algorithm based on shifting the histogram of logarithmic DCT
coefficients of the luminance component. The novelty of this work lies in utilizing both the spatial domain histogram
concept and transform domain enhancement techniques to perform the enhancement. This paper also demonstrates a
quantitative measurement based upon contrast entropy to choose the optimal parameters and determines the
effectiveness of the method. In addition, different color spaces including HSV, YCbCr, and Principle Component
Analysis (PCA) have been examined for the algorithm to determine the best visual results. We also present a
comprehensive review of four commonly used color image enhancement techniques, such as mutiscale retinex with
color restoration, multi contrast enhancement, multi contrast enhancement with dynamic compression and color image
enhancement by scaling, and compare them with the proposed histogram shifting techniques. Computer simulations and
analysis show that the histogram shifting method outperforms the commonly used methods for most images.
This paper presents a new technique for color enhancement based on manipulation of the histogram of logarithmic
transform coefficients. The proposed technique is simple but more effective than some existing techniques in most case.
This method is based on the properties of the histogram of DCT coefficients, also use the fact that the relationship
between stimulus and perception is logarithmic and can afford a marriage between enhancement qualities and
computational efficiency. A human visual system-based quantitative measurement of image contrast improvement is
also used to determine the optimal parameters for the algorithm. A number of experimental results are presented to
illustrate the performance of the proposed algorithm.
This paper proposes two image enhancement algorithms that are based on utilizing histogram data gathered from
wavelet transform domain coefficients. Computer simulations demonstrate that combining the spatial method of
histogram equalization with the logarithmic transform domain coefficient histograms achieves a much more balanced
enhancement, which outperforms classical histogram equalization algorithms.
Much of the success of small unmanned air vehicles (UAVs) has arguably been due to the widespread availability of
low-cost, portable autopilots. While the development of unmanned ground vehicles (UGVs) has led to significant
achievements, as typified by recent grand challenge events, to date the UGV equivalent of the UAV autopilot
is not available. In this paper we describe our recent research aimed at the development of a generic UGV
autopilot. Assuming we are given a drive-by-wire vehicle that accepts as inputs steering, brake, and throttle
commands, we present a system that adds sonar ranging sensors, GPS/IMU/odometry, stereo camera, and
scanning laser sensors, together with a variety of interfacing and communication hardware. The system also
includes a finite state machine-based software architecture as well as a graphical user interface for the operator
control unit (OCU). Algorithms are presented that enable an end-to-end scenario whereby an operator can view
stereo images as seen by the vehicle and can input GPS waypoints either from a map or in the vehicle's scene-view
image, at which point the system uses the environmental sensors as inputs to a Kalman filter for pose estimation
and then computes control actions to move through the waypoint list, while avoiding obstacles. The long-term
goal of the research is a system that is generically applicable to any drive-by-wire unmanned ground vehicle.