Terrain Editing Tutorial: Giants GRLE Converter for Farming Simulator 17 (FS17) by PMC.
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FS17 terrain editing, HOWTO convert GDM and GRLE giants format images to PNG using GRLEConverter program.
Get it from Giants Developer Network (GDN). You should know that Giants Editor FS17 will convert PNG to proper either GRLE or GDM when saving a terrain file.
Convert GRLE (or GDM heh) are cultivator_density and fruit_density. Convert them to PNG and delete the original files, then load your map01 with Giants Editor and just save it, that generates new GRLE/GDM cultivator_density and fruit_density files.
Convert list:
GRLEConverter only converts GDM and GRLE to PNG, it does not convert PNG to GDM, just use GE for that.