Showing papers on "Top-hat transform published in 1983"

Reduction of blocking effect in image coding

Abstract: In some important image coding techniques, such as transform coding, an image is first divided into subimages, and then each subimage is coded independently. The segmentation procedure has significant advantages, but when used in a low bit rate scheme, an undesirable side effect can occur. Specifically, when the image is reconstructed at the decoder, a "blocking effect" can develop due to discontinuities between the subimages. Two methods are developed to reduce the blocking effect. The performance of these methods when applied to a Discrete Cosine Transform image coder is discussed.

Approximating point-set images by line segments using a variation of the Hough transform

Abstract: A transform method is presented for the detection of curves in noisy point-set images and is used to detect line segments in such images. The results of this transform are compared with results from the Hough transform

Image processing method based on processing of interrelated image gradients

Abstract: An improved image processing method prevents unwanted processing artifacts from degrading the reproduction of an image by stressing the interrelationship of various image gradients in the image. Image signals are generated representative of the light value of elements of the image. A local gradient signal is generated in response to a combination of image signals representative of an image gradient over a local portion of the image. An extended gradient signal is also generated representative of an image gradient over an image portion greater than the local portion. The image gradients are interrelated in a composite signal generated from a combination of the local and extended gradient signals. As an example of the combination, the composite signal is made to vary as a function of the difference between the gradient signals. The image signals are then modified subject to a characteristic of the composite signal, e.g., the magnitude of the composite signal.

Energy processing and coding factors in texture discrimination and image processing

Abstract: In this paper two specific questions are considered: (1) When image energy is defined in terms of orientation and frequency components of the image spectrum, how much energy is detected as a function of contrast? (2) Does the visual system have a limited resolution for image orientation and frequency components which define the psychophysical upper limits for two dimensional image coding units? To examine these two questions, experiments were conducted with both black/white and gray-scaled images. The results indicate a monotonic relationship between image contrast and energy processed. Finally, results demonstrate that the upper lindts (or resolution) for discriminable spectral orientation and spatial frequency are approximately 5 deg and 1/8 octave, respectively. Image domain demonstrations confirm these results.

An Image Transform Coding Scheme Based on Spatial Domain Considerations

Abstract: Image transform coding is first briefly reviewed using conventional viewpoints. Then a new spatial domain interpretation is given to image transform coding. An improvement based on this viewpoint for the Fourier transform coding, which possesses simple spatial domain relations, is presented.

A two-component image coding scheme based on two-dimensional interpolation and the discrete cosine transform

Abstract: An image coding algorithm is developed which exploits some of the desirable features of the spatial and the transform domains for image data compression. This scheme is based on a two-component source model similar to some previous results [1 ,2] , but has been generalized to include two-dimensional interpolation and transform coding. Rather than processing successive scan lines of image intensity, this algorithm approximates the image intensity over adjacent subpictures using a two-dimensional polynomial and codes the residual intensities using a discrete cosine transform (DCT). Compression results with rates in the 0.5 to 1.0 bits per pixel range are demonstrated by reconstructed images and rate-distortion characteristics.

Application of sine transform in image processing

Abstract: The sine transform has frequently been suggested as an alternative to the more commonly used Walsh-Hadamard and discrete cosine transforms for the purpose of image coding. It is demonstrated here that there are fundamental theoretical drawbacks to the transform which result in poor performance when it is employed in a practical coding situation.

Simple method for image deblurring

Abstract: A simple method for restoration of linearly blurred images is described utilizing a weak reference beam, coherence spoiling in one dimension, and a provision for scale change. Experimental results are given.

Stationary transform processing of digital images for data compression.

Abstract: A radiometric/geometric transform has been developed which generates images with approximately wide-sense stationary first (mean)- and second (autocorrelation)-order statistics [ R. N. Strickland , Appl. Opt.22, 1462 ( 1983)]. The transform is found to enhance the performance of predictive coding. The radiometric transform reduces radiometric redundancy in the image data and, therefore, aids efficient quantization at low bit rates. A spatial transformation, or warp, is applied to produce nearly uniform autocorrelation length throughout the data. This affords a convenient means of reducing spatial redundancy by varying the spatial resolution in the transformed image. Final bit rates of ~0.6 bits/pixel are realized for high-quality images. We discuss hybrid digital/optical implementation of the stationary transforms for data compression.

A New Class of Image Transforms

Abstract: A new class of image transforms is presented. A special case, a "naturalness preserving" transform, is developed and studied and its potential indicated. Specific on-going research is summarized.