4 research outputs found
Stereoscopic high dynamic range imaging
Two modern technologies show promise to dramatically increase immersion in
virtual environments. Stereoscopic imaging captures two images representing
the views of both eyes and allows for better depth perception. High dynamic
range (HDR) imaging accurately represents real world lighting as opposed to
traditional low dynamic range (LDR) imaging. HDR provides a better contrast
and more natural looking scenes. The combination of the two technologies in
order to gain advantages of both has been, until now, mostly unexplored due to
the current limitations in the imaging pipeline. This thesis reviews both fields,
proposes stereoscopic high dynamic range (SHDR) imaging pipeline outlining the
challenges that need to be resolved to enable SHDR and focuses on capture and
compression aspects of that pipeline.
The problems of capturing SHDR images that would potentially require two
HDR cameras and introduce ghosting, are mitigated by capturing an HDR and
LDR pair and using it to generate SHDR images. A detailed user study compared
four different methods of generating SHDR images. Results demonstrated that
one of the methods may produce images perceptually indistinguishable from the
ground truth.
Insights obtained while developing static image operators guided the design
of SHDR video techniques. Three methods for generating SHDR video from an
HDR-LDR video pair are proposed and compared to the ground truth SHDR
videos. Results showed little overall error and identified a method with the least
error.
Once captured, SHDR content needs to be efficiently compressed. Five SHDR
compression methods that are backward compatible are presented. The proposed
methods can encode SHDR content to little more than that of a traditional single
LDR image (18% larger for one method) and the backward compatibility property
encourages early adoption of the format.
The work presented in this thesis has introduced and advanced capture and
compression methods for the adoption of SHDR imaging. In general, this research
paves the way for a novel field of SHDR imaging which should lead to improved
and more realistic representation of captured scenes
New Remote Sensing Methods for Detecting and Quantifying Forest Disturbance and Regeneration in the Eastern United States
Forest disturbances, such as wildfires, the southern pine beetle, and the hemlock woolly adelgid, affect millions of hectares of forest in North America with significant implications for forest health and management. This dissertation presents new methods to quantify and monitor disturbance through time in the forests of the eastern United States using remotely sensed imagery from the Landsat family of satellites, detect clouds and cloud-shadow in imagery, generate composite images from the clear-sky regions of multiple images acquired at different times, delineate the extents of disturbance events, identify the years in which they occur, and label those events with an agent and severity. These methods operate at a 30x30 m spatial resolution and a yearly temporal resolution. Overall accuracy for cloud and cloud-shadow detection is 98.7% and is significantly better than a leading method. Overall accuracy for designating a specific space and time as disturbed, stable, or regenerating is 85%, and accuracy for labeling disturbance events with a causal agent ranges from 42% to 90%, depending on agent, with overall accuracy, excluding samples marked as `uncertain\u27, of 81%. Due to the high spatial resolution of the imagery and resulting output, these methods are valuable for managers interested in monitoring specific forested areas. Additionally, these methods enable the discovery and quantification of forest dynamics at larger spatial scales in a way other datasets cannot. Applying these methods over the entire extent of the eastern United States highlands reveals significant differences in disturbance frequency by ecoregion, from less than 1% of forested area per year in the Central Appalachians, to over 5% in the Piedmont. Yearly variations from these means are substantial, with disturbance frequency being twice as high as the mean in some years. Additionally, these analyses reveal that some disturbance agents, such as the southern pine beetle, exhibit periodic dynamics. Finally, although these methods are applied here to the problem of forest disturbance in the eastern United States, the core innovations are easily extended to other locations or even to other applications of landscape change, such as vegetation succession, shifting coastlines, or urbanization
Greyscale Photograph Geometry Informed by Dodging and Burning
Abstract. Photographs are often used as input to image processing and computer vision tasks. Prints from the same negative may vary in intensity values due, in part, to the liberal use of dodging and burning in photography. Measurements which are invariant to these transformations can be used to extract information from photographs which is not sensitive to certain alterations in the development process. These measurements are explored through the construction of a differential geometry which is itself invariant to linear dodging and burning.
Using MapReduce Streaming for Distributed Life Simulation on the Cloud
Distributed software simulations are indispensable in the study of large-scale life models but often require the use of technically complex lower-level distributed computing frameworks, such as MPI. We propose to overcome the complexity challenge by applying the emerging MapReduce (MR) model to distributed life simulations and by running such simulations on the cloud. Technically, we design optimized MR streaming algorithms for discrete and continuous versions of Conway’s life according to a general MR streaming pattern. We chose life because it is simple enough as a testbed for MR’s applicability to a-life simulations and general enough to make our results applicable to various lattice-based a-life models. We implement and empirically evaluate our algorithms’ performance on Amazon’s Elastic MR cloud. Our experiments demonstrate that a single MR optimization technique called strip partitioning can reduce the execution time of continuous life simulations by 64%. To the best of our knowledge, we are the first to propose and evaluate MR streaming algorithms for lattice-based simulations. Our algorithms can serve as prototypes in the development of novel MR simulation algorithms for large-scale lattice-based a-life models.https://digitalcommons.chapman.edu/scs_books/1014/thumbnail.jp