Some 3x3 filters for XnView

omniplex wrote:This is a stupid question, but what are these "user defined filters", what are the rules to create something that might be interesting or even useful?

• XnView Forum
  
  • Filter - Custom
• Claude “Clo” Charries: XnView English Help Manual
  
  • Functions details » Customized effect-filters
• Wikipedia
  
  • Kernel (image processing)
• GIMP User Manual
  
  • Convolution Matrix