Mr. Carlos A. Jacanamejoy Profile

Carlos A. Jacanamejoy

at Univ de Ibagué

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Publications (2)

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Proceedings Article | 1 August 2021 Presentation + Paper

Phase congruency implementation in ImageJ using Radix-2 FFT

Carlos Jacanamejoy, Manuel Forero

Proceedings Volume 11842, 118421E (2021) https://doi.org/10.1117/12.2594787

KEYWORDS: Image filtering, Fourier transforms, Edge detection, Image processing, Linear filtering, Image analysis, Software development

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Automatic edge detection in images is an area of great interest to industry and the scientific community. A problem usually experienced is that edge detectors are sensitive to the magnitude of changes in brightness. However, this disadvantage disappears when employing the technique known as phase congruency, which allows edge detection in an image regardless of its illumination level. This technique is based on phase alignment of frequency components. This principle states that the edges of an image occur when the phases of the Fourier components coincide. By using phase, the direct dependence on brightness intensity in edge detection is avoided. A difficulty of phase congruency implemented with monogenic filters is that it requires the computation of the complex Fourier transform. However, its computational cost is high. There are some approaches that seek to reduce its cost, such as the FHT, but they only allow to obtain the Fourier transform of real images. Due to this limitation, methods based on phase congruency were not available in several image processing tools, such as ImageJ, a program widely used by biologists and microscopists for the analysis of biological images, since these programs make use mainly of the Fast Hartley Transform transformation. Therefore, in this work the implementation of phase congruency for ImageJ with monogenic filters using the Fourier Radix-2 FFT transform is described. The results obtained with the proposed implementation were compared with those found with the Kovesi code in GNU Octave, showing that both implementations obtain equivalent results and even better with the proposed method when at least one side of the images is not a power of two, in which case tile-mirror is used to complete the image.

Proceedings Article | 1 August 2021 Presentation + Paper

Study of phase congruency quantization function properties for image edge detection

Manuel Forero, Carlos Jacanamejoy, Santiago Rivera-Nieto

Proceedings Volume 11842, 118421G (2021) https://doi.org/10.1117/12.2594759

KEYWORDS: Quantization, Edge detection, Image segmentation, Image analysis, Image processing, Signal detection, Photography, Image quality, Phase measurement

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Phase congruency is a recently developed, but still rather unexplored and unknown technique for edge detection, allowing to determine the location of edges, ridges and valleys in images by analyzing the phase of the signal's frequency components. Phase congruency identifies edges based on the phase of the signal's frequency components. One of its main uses is image segmentation where the region of interest is separated from the background. The segmentation result varies according to a mathematical function, used to quantify the phase congruency, whose main properties are that it is centered at the origin, of even symmetry and whose global maximum is one. In addition, according to its form, a function allows better edge detection. Thus, several mathematical functions fulfill the necessary conditions for measuring phase congruency. However, these conditions have not yet been studied and, therefore, the type of changes they produce in phase congruency when varying this function is unknown. Therefore, in this work, an evaluation of the characteristics of the functions used for the quantification of phase congruency is presented, observing their properties and the behavior of phase congruency, allowing to find the most appropriate functions depending on the type of edges to be detected.

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