filtre gamma

OBS: Pour le lissage et le déchatoiement des images, ce filtre surclasse tous les autres filtres.
OBS: filtre gamma : terme uniformisé par le Groupe de travail de la terminologie de RADARSAT-2 (GTTR).

CONT: The Gamma filter performs gamma map filtering. Gamma filtering is primarily used on radar data to remove high frequency noise (speckle) while preserving high frequency features (edges). The Gamma Map filter was first proposed by Kuan. ... Lopes modified the Kuan Map filter by assuming a gamma distributed scene and setting up two thresholds. The gamma filter size ranges from 1 to 11. Different filter sizes will greatly affect the quality of processed images. If the filter is too small, the noise filtering algorithm is not effective. If the filter is too large, subtle details of the image will be lost in the filtering process. A 7x7 filter usually gives the best results. ... The GAMMA filter performs spatial filtering on each individual pixel in an image using the grey level values in a square window surrounding each pixel. The dimensions of the filter must be odd, and can be from 3x3 to 11x11 pixels.
CONT: Gamma Filter yields the best smoothing and despeckling. Moreover, it seems to keep the edges without blurring the minimum. Eight textures are applied, based on the cooccurrence matrix. These textures include mean, variance, homogeneity, contrast, dissimilarity, entropy, second moment, and correlation.