# 3.4.5.2. Classification dilation¶

Classification dilation

This tab allows for dilating the border of a class patch, defining the class values to be dilated and the number of pixels from the border. It is useful for classification refinement.

This tool supports virtual raster output; if the output file name ends with .vrt then the output is created as virtual raster composed of as many .tif files as the number of CPU threads defined in System; for large rasters this can speed up the process.

## 3.4.5.2.1. Classification dilation¶

• Select the classification : select a raster (already loaded in QGIS);
• : refresh layer list;
• Class values : set the class values to be dilated; class values must be separated by , and - can be used to define a range of values (e.g. 1, 3-5, 8 will select classes 1, 3, 4, 5, 8); if the text is red then the expression contains errors;
• Size in pixels : number of pixels to be dilated from the border;
• Circular : if checked, the dilation will be circular, similar to a buffer;
• BATCH : add this function to the Batch;
• RUN : choose the output destination and start the calculation;