Modding Tutorial: Snow/frozen textures in Gimp 2.8 video - ZoneExpanded - Road To The North mod for S.T.A.L.K.E.R.: Call of Pripyat
"RTTN has that Roadside Picnic feeling. Everyone entered the Zone for their own reasons and everyone is connected to eachother in some way. The game adapts to your choices and world events, changing dialogs and missions. Characters you meet have their own interests and personalities, some will tell you their story. Everything included is lorefriendly to stalker, based on the information we can find in the original games and will take you on a well written journey. The world's size allows you to choose your own path, the order in which you play missions and write your own story as well. The Zone is an unforgiving place and it will be difficult to survive. Take your time, explore, roleplay and.. Good hunting, Stalker."
This is how I made the frozen maps for the winter pack, in Gimp 2.8
The most useful function while editing was Shift+O (select on color)
and "stroke selection" from the top menu, to make selected edges softer.
I use a very soft white brush on the water to make it appear frozen,
and a hard vegetation brush 100% opacity + jitter for snow. This looks good because I first select an area with shift+O before painting