RadGridView filtering by image column

Hello, Zygmunt,

The GridViewImageColumn is not supposed to provide filtering functionality out of the box. However, the following KB article demonstrates a sample approach how you can implement your own filtering functionality for a column type that does not support filtering. A similar solution may be adopted for the image column as well:

https://docs.telerik.com/devtools/winforms/knowledge-base/filter-commandcolumn-in-gridview 

An alternative solution is to use the simple text column, hide the text and show an image by using the CellFormatting event. Thus, the filtering will work of of the box considering the cell's text even though it is not visible.

I hope this information helps. If you need any further assistance please don't hesitate to contact me. 

Regards,
Dess | Tech Support Engineer, Principal
Progress Telerik