i.zc Zero-crossing "edge detection" raster function for image processing. Imagery (i.*) ParameterRaster|input|Name of input raster map|False ParameterNumber|width|x-y extent of the Gaussian filter|1|None|9 ParameterNumber|threshold|Sensitivity of Gaussian filter|0|None|10.0 ParameterNumber|orientations|Number of azimuth directions categorized|0|None|1 OutputRaster|output|Zero crossing