DirectDraw Surface (DDS) converter

DDS, DirectDraw Surface, is Microsoft's container for GPU textures. A file starts with the four bytes "DDS " and a 124-byte header giving size, pixel format and flags, optionally followed by a DX10 header with a DXGI format number, then the texture data. That data is usually block-compressed: DXT1 (BC1), DXT3 (BC2) and DXT5 (BC3) for colour with or without alpha, BC4 and BC5 for one- and two-channel maps such as normals, BC6H for HDR lighting and BC7 for high-quality colour. A single file can also hold a full mip chain, the six faces of a cubemap, a texture array or a volume.

DDS files come from games and game engines. Modders open them to recolour skins and armour, artists inspect them when debugging a material, and asset rippers export them by the thousand. Windows Explorer, browsers and most image viewers do not show them, which is why people look for DDS to PNG.

Our image engine decodes the largest mip level of the first surface. In our tests DXT1, DXT3, DXT5, BC5, BC6H, BC7 and uncompressed DDS all opened, from three.js example textures and Pillow's test set. The smaller mip levels are not exported, and in a cubemap only the first of six faces is: a 786,560-byte skybox produced one 512×512 PNG. BC5 normal maps come out red and green with a blue channel of 0, because the format stores only two channels, and BC6H HDR values are clipped to 8-bit colour.

Converting is one-way for now. We do not write DDS: a texture that goes back into a game needs the compression format and mip chain that game expects, which texconv, Paint.NET, GIMP or the game's own tools produce. Keep the PNG as your editable working copy and export to DDS at the end.