Focal Filters - MapInfo_Pro_Advanced - 2023

Focal filter is an image enhancement techniques that enables you to process an image to improve its appearance. Filter reduces the noise from the image. Focal filter supports only continuous and classified rasters.

MapInfo Pro Advanced supports the following focal filter methods:

• Minimum - It searches the minimum value for each cell location within a specified neighborhood in the input raster and writes it to the corresponding cell location in the output raster. For example, to find out the minimum value in a 3 x 3 neighborhood around the center cell, see the illustration below:
  

  

  
  In the above illustration of a 3 x 3 neighborhood, the sorted cell values would be: 0, 1, 2, 2, 2, 3, 3, 4, 4. Since the minimum (smallest) value in this matrix is 0, so 0 will be written to the corresponding cell location in the output raster. The output raster band data type would be same as the input raster band data type. For example, if the values in the input raster are in floating point, the values in the output raster will be floating point. This method supports only continuous raster.

• Maximum - It searches the maximum value for each cell location within a specified neighborhood in the input raster and writes it to the corresponding cell location in the output raster. For example, to find out the maximum value in a 3 x 3 neighborhood around the center cell, see the illustration below:

  
  

  

  
  

  In the above illustration of a 3 x 3 neighborhood, the sorted cell values would be: 0, 1, 2, 2, 2, 3, 3, 4, 4. Since the maximum (largest) value in this matrix is 4, so 4 will be written to the corresponding cell location in the output raster. The output raster band data type would be same as the input raster band data type. For example, if the values in the input raster are in floating point, the values in the output raster will be floating point. This method supports only continuous raster.

• Majority - It calculates the majority value (the value that appears most often) for each cell location within a specified neighborhood in the input raster and writes it to the corresponding cell location in the output raster. For example, to calculates the majority value in a 3 x 3 neighborhood around the center cell, see the illustration below:

  
  

  

  
  

  In the above illustration of a 3 x 3 neighborhood, the sorted values are: 0, 1, 2, 2, 2, 3, 3, 4, 4. There are three instances of 2, which is the majority. So 2 will be written to the corresponding cell location in the output raster. The output raster band data type would be same as the input raster band data type. For example, if the values in the input raster are in floating point, the values in the output raster will be floating point.

  • If two or more cell values have same number of occurrences in the neighborhood of a processing cell, a Null cell value will be written to the corresponding cell location in the output raster.
  • Majority focal filter supports both continuous and classified rasters.

• Standard Deviation - It calculates the standard deviation of neighboring cell values for each cell location in the input raster and writes it to the corresponding cell location in the output raster. For example, to calculates the standard deviation in a 3 x 3 neighborhood around the center cell, see the illustration below:

  
  

  

  
  
  The standard deviation is calculated by the following formula: