KEYWORDS: Image segmentation, Image processing algorithms and systems, Color image segmentation, Color image processing, Electrical engineering, Human vision and color perception, Electronic imaging, Image processing, RGB color model, Radiation oncology
We propose a novel algorithm for unsupervised segmentation of color images. The proposed approach utilizes a dynamic
color gradient thresholding scheme that guides the region growing process. Given a color image, a weighted vectorbased
color gradient map is generated. Seeds are identified and a dynamic threshold is then used to perform reliable
growing of regions on the weighted gradient map. Over-segmentation, if any, is addressed by a Similarity Measurebased
region merging stage to produce the final segmented image. Comparative results demonstrate the effectiveness of
this algorithm for color image segmentation.
Ultrasound-induced blood stasis was demonstrated thirty years ago. Most of the literature has been focused on methods employed to prevent stasis from occurring during ultrasound imaging. The current work discusses some of the theory behind this phenomenon. It also demonstrates ultrasound-induced blood stasis in murine tumor and muscle tissue, observed through noninvasive measurements of optical spectroscopy, and discusses possible diagnostic uses. We demonstrate that, using optical spectroscopy, effects of ultrasound can be used to noninvasively differentiate tumor from muscle tissue in mice, and that we can quantitatively differentiate tumor from muscle with maximum specificity 0.83, maximum sensitivity 0.79, and area under ROC curve 0.90, using a simple algorithm.
Linear Pixel Shuffling (LPS) dithering produces blue-noise-like patterns, but the placement of thresholds in a dither matrix is a result of an exact algebra, rather than iterative procedure -- as is usually the case. In this paper, we investigate the potential use of LPS for construction of color (CMYK) dithering masks.
In case of LPS dithering, the addition of the same value to each mask threshold, using modular arithmetic, is equivalent to the spatial mask shift. We propose a set of three shifted color masks for C, M, and Y that we construct from the original LPS mask using modular arithmetic. The main advantage of this approach is its simplicity. These shifts can be "tailored" to the statistical properties of the image and the set of new screens can be calculated on the fly.
The proposed method enables creation of screens of arbitrary size, since the dithering masks are tiled automatically (actually, the masks are of unlimited size). The number of gray levels in each screen is limited by the choice of a modulus number used for mask thresholds calculation. This enables us to use a virtually unlimited number of thresholds that are not necessarily linearly related to the LPS calculated matrix values. Thus, it is relatively easy to construct a non-linear dither screen that will compensate for any printer non-linearity.
The William Blake Archive is part of an emerging class of electronic projects in the humanities that may be described as hypermedia archives. It provides structured access to high-quality electronic reproductions of rare and often unique primary source materials, in this case the work of poet and painter William Blake. Due to the extensive high frequency content of Blake's paintings (namely, colored engravings), they are not suitable for very efficient compression that meets both rate and distortion criteria at the same time. Resolving that problem, the authors utilized modified Mixed Raster Content (MRC) compression scheme -- originally developed for compression of compound documents -- for the compression of colored engravings. In this paper, for the first time, we have been able to demonstrate the successful use of the MRC compression approach for the compression of colored, engraved images. Additional, but not less important benefits of the MRC image representation for Blake scholars are presented: because the applied segmentation method can essentially lift the color overlay of an impression, it provides the student of Blake the unique opportunity to recreate the underlying copperplate image, model the artist's coloring process, and study them separately.
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