Niranjan Damera-Venkata

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We model a degraded image as an original image that has been subject to linear frequency distortion and additive noise injection. Since the psychovisual effects of frequency distortion and noise injection are independent, we decouple these two sources of degradation and measure their effect on the human visual system. We develop a distortion measure (DM) of(More)
Error diffusion halftoning is a popular method of producing frequency modulated (FM) halftones for printing and display. FM halftoning fixes the dot size (e.g., to one pixel in conventional error diffusion) and varies the dot frequency according to the intensity of the original grayscale image. We generalize error diffusion to produce FM halftones with(More)
Halftones and other binary images are difficult to process with causing several degradation. Degradation is greatly reduced if the halftone is inverse halftoned (converted to grayscale) before scaling, sharpening, rotating, or other processing. For error diffused halftones, we present (1) a fast inverse halftoning algorithm and (2) a new multiscale gradient(More)
Grayscale digital image halftoning quantizes each pixel to one bit. In error diffusion halftoning, the quantization error at each pixel is filtered and fed back to the input in order to diffuse the quantization error among the neighboring grayscale pixels. Error diffusion introduces nonlinear distortion (directional artifacts), linear distortion(More)
We present a fast, non-iterative technique for producing grayscale images from error diiused and dithered halftones. The rst stage of the algorithm consists of a Gaussian l-ter and a median lter, while the second stage consists of a bandpass lter, a thresholding operation, and a median lter. The second stage enhances the rendering of edges in the inverse(More)
We present a general framework for the modeling and optimization of scalable multi-projector displays. Based on this framework, we derive algorithms that can robustly optimize the visual quality of an arbitrary combination of projectors without manual adjustment. When the projectors are tiled, we show that our framework automatically produces blending maps(More)
We consider the problem of rendering high-resolution images on a display composed of multiple superimposed lower-resolution projectors. A theoretical analysis of this problem in the literature previously concluded that the multi-projector superimposition of low resolution projectors cannot produce high resolution images. In our recent work, we showed to the(More)
We present a generalized optimal minimum phase digital FIR lter design algorithm that supports 1 arbitrary magnitude response speciications, 2 high coeecient accuracy, and 3 real and complex lters. The algorithm uses the Discrete Hilbert Transform relationship between the magnitude spectrum of a causal real sequence and its minimum phase delay phase(More)