Showing papers on "Image gradient published in 1977"
TL;DR: The concepts of art “edge activity index” and a “locally adaptive threshold” are introduced and shown to improve the performance of this method as well as other edge operators such as Kitsch and Sobel.
245 citations
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TL;DR: The compass gradient edge detection method developed by the author for monochrome images is extended to color edge detection and a quantitative measure is discussed in choosing the color coordinates for edge extraction.
Abstract: The choice of the color coordinates for extraction of visually significant edges and boundaries in a color image is discussed. The compass gradient edge detection method developed by the author for monochrome images is extended to color edge detection and a quantitative measure is discussed in choosing the color coordinates for edge extraction.
186 citations
01 Jan 1977
TL;DR: The proposed quantification method can be used for edge detection, texture analysis, and classification, as well as feature extraction, through the use of a resolution-dependent feature extraction process.
Abstract: A picture processing scheme which quantifies pictorial information through the use of a resolution-dependent feature extraction process is introduced. The proposed quantification method (based on an information theoretical approach) can be used for edge detection, texture analysis, and classification, as well as feature extraction. These applications are possible because the information measures obtained are capable of uncovering some basic characteristics of images. Vector quantities and synthesized plots of various information measures derived from images are included here to demonstrate the usefulness of the method in image analysis.
31 citations
TL;DR: A new image coding system which combines the detection and coding of visually significant edges in natural images and the concepts of an "edge activity index" and a "locally adaptive threshold" are introduced and shown to improve the performance even further.
Abstract: This paper describes a new image coding system which combines the detection and coding of visually significant edges in natural images. The edges are defined as amplitude discontinuities between different regions of an image. The edge detection system makes use of 3 x 3 masks, which are well suited for digital implementation. Edge angles are quantized to eight equally spaced directions, suitable for chain coding of contours. Use of an edge direction map improves the simple thresholding of gradient modulus images. The concept of local connectivity of the edge direction map is useful in improving the performance of this method as well as other edge operators such as Kirsch and Sobel. The concepts of an "edge activity index" and a "locally adaptive threshold" are introduced and shown to improve the performance even further.
26 citations
01 Dec 1977
TL;DR: The technique is viewed as a low-level operator in the context of the more complex problem, that of scene analysis, and a conceptual comparison with some previous edge detectors is done.
Abstract: A new edge detection technique for digital image processing is presented. The technique is viewed as a low-level operator in the context of the more complex problem, that of scene analysis, and a conceptual comparison with some previous edge detectors is done. The new edge detection technique has been implemented and its results are compared with two other edge detection techniques using the same kind of pictures as input data. The software implementation of this new edge detector written in machine language takes 32 s for an image of size 128 by 128 picture elements. The edge detector can be hardware-implemented and such an implementation, for which the estimated processing time will be about half a second, is given in the Appendix.
18 citations