This tool performs a conservative smoothing filter on a raster image. A conservative smoothing filter can be used to remove short-range variability in an image, effectively acting to smooth the image. It is particularly useful for eliminating local spikes and reducing the noise in an image. The algorithm operates by calculating the minimum and maximum neighbouring values surrounding a grid cell. If the cell at the centre of the kernel is greater than the calculated maximum value, it is replaced with the maximum value in the output image. Similarly, if the cell value at the kernel centre is less than the neighbouring minimum value, the corresponding grid cell in the output image is replaced with the minimum value. This filter tends to alter an image very little compared with other smoothing filters such as the mean filter, the edge-preserving smoothing filter (bilateral), median, Gaussian, or Olympic filters.
Neighbourhood size, or filter size, is determined by the user-defined x and y dimensions. These dimensions should be odd, positive integer values, e.g. 3, 5, 7, 9... The user may also define the neighbourhood shape as either squared or rounded. A rounded neighbourhood approximates an ellipse; a rounded neighbourhood with equal x and y dimensions approximates a circle.
NoData values in the input image are ignored during filtering. When the neighbourhood around a grid cell extends beyond the edge of the grid, NoData values are assigned to these sites. The output raster is of the float data type and continuous data scale.
The following is an example of a Python script that uses this tool:
wd = pluginHost.getWorkingDirectory()
inputFile = wd + "input.dep"
outputFile = wd + "output.dep"
xDim = "3"
yDim = "3"
rounded = "false"
reflectEdges = "true"
args = [inputFile, outputFile, xDim, yDim, rounded, reflectEdges]
pluginHost.runPlugin("FilterConservativeSmoothing", args, False)
This is a Groovy script also using the tool:
def wd = pluginHost.getWorkingDirectory()
def inputFile = wd + "input.dep"
def outputFile = wd + "output.dep"
def xDim = "7"
def yDim = "7"
def rounded = "true"
def reflectEdges = "true"
String[] args = [inputFile, outputFile, xDim, yDim, rounded, reflectEdges]
pluginHost.runPlugin("FilterConservativeSmoothing", args, false)