Finding a given object in an image or a sequence of frames is one of the fundamental computer vision challenges. Humans can recognize a multitude of objects with little effort despite scale, lighting and perspective changes. A robust computer vision based object recognition system is achievable only if a considerable tolerance to change in scale, rotation and light is achieved. Partial occlusion tolerance is also of paramount importance in order to achieve robust object recognition in real-time applications. In this paper, we propose an effective method for recognizing a given object from a class of trained objects in the presence of partial occlusions and considerable variance in scale, rotation and lighting conditions. The proposed method can also identify the absence of a given object from the class of trained objects. Unlike the conventional methods for object recognition based on the key feature matches between the training image and a test image, the proposed algorithm utilizes a statistical measure from the homography transform based resultant matrix to determine an object match. The magnitude of determinant of the homography matrix obtained by the homography transform between the test image and the set of training images is used as a criterion to recognize the object contained in the test image. The magnitude of the determinant of homography matrix is found to be very near to zero (i.e. less than 0.005) and ranges between 0.05 and 1, for the out-of-class object and in-class objects respectively. Hence, an out-of-class object can also be identified by using low threshold criteria on the magnitude of the determinant obtained. The proposed method has been extensively tested on a huge database of objects containing about 100 similar and difficult objects to give positive results for both out-of-class and in-class object recognition scenarios. The overall system performance has been documented to be about 95% accurate for a varied range of testing scenarios.
An improvement to the wavelet-modified Optimal Trade-off Maximum Average Correlation Height (OT-MACH) filter
with the use of the Rayleigh distribution filter is proposed. The Rayleigh distribution filter is applied to the OT-MACH
filter to provide a sharper low frequency cut-off than the Laplacian of Gaussian based wavelet filter that has been
previously reported to enhance OT-MACH filter performance. Filters are trained using a 3D CAD model and tested on
the corresponding real target object in high clutter environments acquired from a Forward Looking Infra Red (FLIR)
sensor. Comparative evaluation of the performance of the original, wavelet and Rayleigh modified OT-MACH filter is
reported for the recognition of the target objects present within the thermal infra-red image data set.
A wavelet-modified frequency domain Optimal Trade-off Maximum Average Correlation Height (OT-MACH) filter has
been trained using 3D CAD models and tested on real target images acquired from a Forward Looking Infra Red (FLIR)
sensor. The OT-MACH filter can be used to detect and discriminate predefined targets from a cluttered background. The
FLIR sensor extends the filter's ability by increasing the range of detection by exploiting the heat signature differences
between the target and the background. A Difference of Gaussians (DoG) based wavelet filter has been use to improve
the OT-MACH filter discrimination ability and distortion tolerance. Choosing the right standard deviation values of the
two Gaussians comprising the filter is critical. In this paper we present a new technique for auto adjustment of the DoG
filter parameters driven by the expected target size. Tests were carried on images acquired by the Apache AH-64
helicopter mounted FLIR sensor, results showing an overall improvement in the recognition of target objects present
within the IR images.
Accurately generating an alarm for a moving door is a precondition for tracking, recognizing and segmenting objects or
people entering or exiting the door. The challenge of generating an alarm when a door event occurs is difficult when
dealing with complex doors, moving cameras, objects moving or an obscured entrance of the door, together with the
presence of varying illumination conditions such as a door-way light being switched on. In this paper, we propose an
effective method of tracking the door motion using edge-map information contained within a localised region at the top
of the door. The region is located where the top edge of the door displaces every time the door is opened or closed. The
proposed algorithm uses the edge-map information to detect the moving corner in the small windowed area with the help
of a Harris corner detector. The moving corner detected in the selected region gives an exact coordinate of the door
corner in motion, thus helping in generating an alarm to signify that the door is being opened or closed. Additionally, due
to the prior selection of the small region, the proposed method nullifies the adverse effects mentioned above and helps
prevent different objects that move in front of the door affecting its efficient tracking. The proposed overall method also
generates an alarm to signify whether the door was displaced to provide entry or exit. To do this, an active contour
orientation is computed to estimate the direction of motion of objects in the door area when an event occurs. This
information is used to distinguish between objects and entities entering or exiting the door. A Hough transform is applied
on a specific region in the frame to detect a line, which is used to perform error correction to the selected windows. The
detected line coordinates are used to nullify the effects of a moving camera platform, thus improving the robustness of
the results. The developed algorithm has been tested on all the Door Zone video sequences contained with the United
Kingdom Home Office i-LIDs dataset, with promising results.
A robust human intrusion detection technique using hue-saturation histograms is presented in this paper. Initially a
region of interest (ROI) is manually identified in the scene viewed by a single fixed CCTV camera. All objects in the
ROI are automatically demarcated from the background using brightness and chromaticity distortion parameters. The
segmented objects are then tracked using correlation between hue-saturation based bivariate distributions. The technique
has been applied on all the 'Sterile Zone' sequences of the United Kingdom Home Office iLIDS dataset and its
performance is evaluated with over 70% positive results.
Detection and tracking of illegally parked vehicles are usually considered as crucial steps in the development
of a video-surveillance based traffic-management system. The major challenge in this task lies in making the
tracking phase illumination-change tolerant. The paper presents a two-stage process to detect vehicles parked
illegally and monitor these in subsequent frames. Chromaticity and brightness distortion estimates are used in
the first stage to segment the foreground objects from the remainder of the scene. The process then locks onto all
stationary 'vehicle'-size patches, parts of which overlap with the regions of interest marked interactively a priori.
The second stage of the process is applied subsequently to track all the illegally parked vehicles detected during
the first stage. All the locked patches are filtered using a difference-of-Gaussian (DoG) filter operated at three
different scales to capture a broad range of information. In succeeding frames patches at the same locations are
similarly DoG filtered at the three different scales and the results matched with the corresponding ones initially
generated. A combined score based on correlation estimates is used to track and confirm the existence of the
illegally parked vehicles. Use of the DoG filter helps in extracting edge based features of the patches thus making
the tracking process broadly illumination-invariant. The two-stage approach has been tested on the United
Kingdom Home Office iLIDS dataset with encouraging results.
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