Showing papers on "Image scaling published in 1986"

Algorithms for subpixel registration

Abstract: This paper presents an analysis of four algorithms which are able to register images with subpixel accuracy; these are correlation interpolation, intensity interpolation, differential method, and phase correlation. The subpixel registration problem is described in detail and the resampling process for subpixel registration is analyzed theoretically. It is shown that the main factors affecting registration accuracy are the interpolation function, sampling frequency, number of bits per pixel, and frequency content of the image. An iterative version of the intensity interpolation algorithm, which achieves maximum computational efficiency, is also presented. Analyses, computer simulations, and experiments for measuring displacements of objects using their speckle images have shown that this algorithm is faster than a direct intensity interpolation algorithm by a factor of more than ten thousand. Using bilinear interpolation and representing pixels by 8-bit samples, a 0.01 to 0.05 pixel registration accuracy can be achieved.

Contour coding of images

Abstract: This paper describes a coding strategy which stores digital images in terms of their contours. The data in the original raw image is reorganised into a set of 1-d trajectories and these are normalised in length and approximated by low rank models. It is the coefficients of these models which are retained. The second order statistical information is used to derive a vector codebook containing standard sets of coefficients, and each contour is allocated the codeword of the nearest standard vector. In this way a codebook of generating functions for standard shapes is obtained. The problems of non closing contours are addressed along with interpolation methods to produce a reconstructed image from a contoured image.

Image Resampling on a Cylindrical Sector Grid

Abstract: A cylindrical sector image grid with equal area pixels for representing tomographic images is described which offers computational advantages for some algebraic and stochastic reconstruction strategies. An evaluation of techniques for resampling from the cylindrical representation to the standard square pixel representation is included. The resampling techniques of nearest-neighbors, bilinear, cubic B spline, two high resolution cubic spline, and overlap weighting are evaluated by their noise propagation, resolution recovery, noise power spectra, and visual appearance.

Time/Space Recursions For Differential Motion Estimation

Abstract: The alqorithms for the measurement of image motion heavily depend on the uniformity of the motion field Block techniques work only if the whole block undergoes the same motion and point-recursive techniques work only if the motion changes smoothly However, in real images motion changes abruptly at the boundaries of the imaged objects Therefore block techniques are unreliable and pointwise recursion techniques have to be driven by proper tests so that the recursions are stopped and reinitialized where necessary, without causing unnecessary smear The paper analyzes such improvements of the pel recursive motion analysis techniques either for coding, with a progressive scan of the image sequence, or for image interpolation

Image Interpolation With Dedicated Digital Hardware

Abstract: Algorithm for interpolating two-dimensional image data to change picture-element spacing implemented in dedicated digital hardware for high-speed execution. System interpolates 100 times as fast as generalpurpose computer. Image resampling occurs first along one image axis and then along other, using two interpolation devices implemented in series.