Contrast Enhancement Based on a Morphological Rational Multiscale Algorithm
Mejora de contraste basada en un algoritmo morfológico racional multiescala
Hayde Peregrina Barreto1 and Iván R. Terol Villalobos2
1 Facultad de Ingeniería, Universidad Autónoma de Querétaro–Campus San Juan del Río Querétaro, México. Email: hperegrina@ieee.org
2 Centro de Investigación y Desarrollo Tecnológico en Electroquímica (CIDETEQ) Querétaro, México. Email: famter@ciateq.net.mx
]]>Article received on July 27, 2009
Accepted on January 06, 2010
Abstract
Contrast enhancement is an important task in image processing and it is commonly used as a preprocessing step in order to improve the results for other tasks such as segmentation. However, not only do some methods for contrast improvement have good performance working on low contrast regions, but they also affect good contrast regions; owing to the fact that some elements could be vanished, representing a loss of information. A method focused on images with different luminance conditions is introduced in the present work. The proposed method is based on morphological filters by reconstruction and rational operations, which together, allow a uniform contrast enhancement. Furthermore, due to the properties of these morphological transformations, the creation of new elements on image is avoided. The processing was made on luminance values in the u'v'Y' color space, which permits to keep the chrominance and to avoid the creation of new colors. As a result of the previous considerations, the proposed method keeps the natural color appearance of the image.
Keywords: Contrast enhancement, Rational operations, Morphological filters, Mathematical morphology.
Resumen
La mejora del contraste es una tarea importante en procesamiento de imágenes y a menudo es usada como paso de pre–procesamiento a fin de mejorar los resultados de procesos como segmentación. Algunos métodos para mejora de contraste tienen un buen desempeño trabajando en regiones con poco contraste pero también afectan las regiones con suficiente contraste; este es un efecto no deseado debido a que algunos elementos de la imagen pueden ser eliminados lo cual representa una pérdida de información. En este trabajo se presenta una mejora de contraste enfocada a imágenes que tienen diferente luminancia sobre la misma escena. El método propuesto está basado en filtros morfológicos por reconstrucción y operaciones racionales, que en conjunto permiten una mejora de contraste uniforme. Además, debido a las propiedades de estas transformaciones morfológicas se evita la creación de nuevos elementos. El procesamiento trabaja sobre los valores de luminancia en el espacio de color u'v'Y', lo cual permite mantener el croma y evitar la creación de nuevos colores. Como resultado de las consideraciones mencionadas, este método provee una mejora de contraste uniforme y mantiene la apariencia natural de la imagen.
]]> Palabras clave: Mejora de contraste, Operaciones racionales, Filtros morfológicos, Morfología matemática.
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Acknowledgements
We would like to thank the anonymous reviewers for their valuable comments. The author Hayde Peregrina–Barreto thanks the government agency CONACyT for the financial support scholarship 206082. This work was funded by the government agency CONACyT (58367), Mexico.
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