(October 16, 2017)
VTFEdit is a tool for viewing, editing, and creating VTF and VMT files. It requires the .NET 2.0 framework to run.
Normal image files (including JPGs, PNGs, and TGAs) can be imported and saved in any number of internal VTF formats, and VTFs can also be exported back out to those formats. VTFEdit also allows a high degree of control over the textures it processes, and anything from VTF flags to mipmap settings can be edited. Bumpmaps can even be generated with the tool.
VTFEdit also allows for batch conversion of loose texture files and textures in WADs, allowing for easy conversion of GoldSrc textures into Source materials.