GIMP + G’MIC
G’MIC is a really useful extension for GIMP and to make it even better, it is dead easy to install.
Originally shared by GIMP
Old pro tip: if you need to remove dust and scratches from your photos, use G’MIC’s plugin called ‘Remove hot pixels’ and tweak its ‘mask size’ and ‘threshold’ settings.
Get G`MIC from http://gmic.eu/gimp.shtml.