Edge enhancement

About: Edge enhancement is a research topic. Over the lifetime, 2324 publications have been published within this topic receiving 30962 citations.

Image contrast enhancement based on intensity-pair distribution

Abstract: Current contrast enhancement algorithms sometimes come with undesired drawbacks, like the loss of tiny details, enhancement of image noise, occasional over-enhancement, and unnatural look of the processed images. In this paper, we propose a new approach for contrast enhancement based on the use of a so-called intensity-pair distribution. This distribution possesses both local information and global information of the image content. By analyzing the content of intensity-pair distribution, a set of expansion forces are generated for contrast enhancement while another set of anti-expansion forces are generated to suppress image noise. To avoid over-enhancement and preserve the natural look of the processed images, a magnitude mapping function is also proposed. Experimental results show that the proposed algorithm does provide a flexible and reliable way for contrast enhancement.

Polarization-based spatial filtering for directional and nondirectional edge enhancement using an S-waveplate

Abstract: Using polarization as an additional parameter apart from amplitude and phase in spatial filtering experiments offers additional advantages and possibilities. An S-waveplate that can convert a linearly polarized light into radially or azimuthally polarized light can also be used for isotropic edge enhancement. For anisotropic edge enhancement, introduction of a polarizer at the output was recommended and edge selection was done by orientation of the polarizer. But the full potential of the S-waveplate as a spatial filter has not been exploited so far. Unlike the standard amplitude and phase-based Fourier filters, which are independent to the state of polarization of the illuminating beam, the S-waveplate acts in a different way depending on the state of polarization. The edge selection does not need to be carried out by changing the orientation of the polarizer. With a fixed polarizer at the output, we show that either isotropic or anisotropic edge enhancement in any desired orientation can be performed by operating the same spatial filter setup in different illuminating polarization states.

Error image in error diffusion

Abstract: The concept of an error image is defined for the error diffusion algorithm. Ordinarily hidden from view, the error image is a visual representation of the internally generated errors from which the algorithm derives its name. In this paper, it is shown that the error image contains a linear component of the input image, which induces edge enhancement in the output error diffusion image. Examples are shown for three different error weight distributions: a 1-D one- ahead distribution, the standard 4-element distribution, and a 12-element error distribution. The amount of edge enhancement in the corresponding algorithm is shown to vary with the amount of input image information present in the error image.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Noise-resistant weak-structure enhancement for digital radiography

Abstract: Today's digital radiography systems mostly use unsharp masking-like image enhancement techniques based on splitting input images into two or three frequency channels. This method allows to enhance very small structures (edge enhancement) as well as enhancement of global contrast (harmonization). However, structures of medium size are not accessible by such enhancement. We develop and test a nonlinear enhancement algorithm based on hierarchically repeated unsharp masking, resulting in a multiscale architecture allowing consistent access to structures of all sizes. The algorithm is noise- resistant in the sense that it prevents unacceptable noise amplification. Clinical tests performed in the radiology departments of two major German hospitals so far strongly indicate the superior performance and high acceptance of the new processing.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A Fast Dynamic Range Compression With Local Contrast Preservation Algorithm and Its Application to Real-Time Video Enhancement

Abstract: This study addresses low dynamic range (LDR) image/video enhancement for digital video cameras. A new fast dynamic range compression format with a local-contrast-preservation (FDRCLCP) algorithm resolves this problem efficiently. The proposed FDRCLCP algorithm can combine with any continuously differentiable intensity transfer function to achieve LDR image enhancement. In combination with the FDRCLCP algorithm, a new intensity-transfer function is proposed, adaptively accomplishing dynamic range compression and edge-contrast enhancement depending on the local mean value of the input luminance image. The proposed method also extends to a linear color remapping approach, not only preserving the original image's color information, but also controlling color saturation of the resulting image. Moreover, a look-up-table (LUT) acceleration approach improves the processing speed of the proposed FDRCLCP algorithm in processing video signals, allowing real-time video enhancement processing. Experimental results show that the proposed method not only provides good visual representation in both quantitative and visual comparisons, but also achieves real-time performance for video processing.