Before you can convert a file, you need to understand what you’re dealing with. RTTEX stands for Real Time Texture. It is a proprietary container format primarily associated with the GIANTS Engine 8, 9, and 10, the engine behind the Farming Simulator series (as well as Professional Farmer and other simulation titles).
Offset Size Description
0x00 4 Magic "RTTX"
0x04 2 Version
0x06 2 Format (DXT1, DXT5, ARGB, etc.)
0x08 4 Width
0x0C 4 Height
0x10 ... Mipmap data + pixel bytes
RTTEX files are often highly compressed (e.g., DXT5 at 4:1 or 8:1 ratio). A lossless PNG will be 3x to 5x larger than the original RTTEX. If disk space is a concern, consider converting to DDS (DirectDraw Surface) instead, which retains the original GPU compression. rttex to png