1 |
Edge directed resolution enhancement and demosaicingPekkucuksen, Ibrahim Ethem 19 August 2011 (has links)
The objective of the proposed research is to develop high performance, low computational complexity resolution enhancement and demosaicing algorithms. Our approach to both problems is to find creative ways to incorporate edge information into the algorithm design. However, in contrast with the usual edge directed approaches, we do not try to detect edge presence and orientation explicitly. For the image interpolation problem, we study the relationship between low resolution and high resolution pixels, and derive a general interpolation formula to be used on all pixels. This simple interpolation algorithm is able to generate sharp edges in any orientation. We also propose a simple 3 by 3 filter that quantifies local luminance transition and apply it to the demosaicing problem. Additionally, we propose a gradient based directional demosaicing method that does not require setting any thresholds. We show that the performance of this algorithm can be improved by using multiscale gradients. Finally, we address the low spectral correlation demosaicing problem by proposing a new family of hybrid color filter array (CFA) patterns and a local algorithm that is two orders of magnitude faster than a comparable non-local solution while offering the same level of performance.
|
2 |
A color filter array interpolation method for digital cameras using alias cancellationAppia, Vikram V. 31 March 2008 (has links)
To reduce cost, many digital cameras use a single sensor array instead of using
three arrays for the red, green and blue. Thus at each pixel location only the red,
green or blue intensity value is available. And to generate a complete color image,
the camera must estimate the missing two values at each pixel location .Color filter
arrays are used to capture only one portion of the spectrum (Red, Green or Blue) at
each location. Various arrangements of the Color Filter Array (CFA) are possible, but
the Bayer array is the most commonly used arrangement and we will deal exclusively
with the Bayer array in this thesis.
Since each of the three colors channels are effectively downsampled, it leads to
aliasing artifacts. This thesis will analyze the effects of aliasing in the frequency-
domain and present a method to reduce the deterioration in image quality due to
aliasing artifacts.
Two reference algorithms, AH-POCS (Adams and Hamilton - Projection Onto
Convex Sets) and Adaptive Homogeneity-Directed interpolation, are discussed in de-
tail. Both algorithms use the assumption that there is high correlation in the high-
frequency regions to reduce aliasing. AH-POCS uses alias cancellation technique to
reduce aliasing in the red and blue images, while the Adaptive Homogeneity-Directed
interpolation algorithm is an edge-directed algorithm. We present here an algorithm
that combines these two techniques and provides a better result on average when
compared to the reference algorithms.
|
Page generated in 0.1336 seconds