DDS to PNG Converter

DDS (DirectDraw Surface) is the texture format of DirectX games and engines: block-compressed, with mipmaps and cube maps, and unreadable by ordinary image viewers. Modders, game artists and anyone extracting textures need them as PNG. This converter reads DDS files in your browser with a built-in decoder and saves the full-size image as a lossless PNG, keeping alpha.

How to use this tool

1. Drop one or more .dds files.
2. Keep transparency or fill it; for BC5 normal maps choose whether to rebuild the blue channel.
3. Optionally set a max size for previews.
4. Download the PNGs — a cube map gives one image per face.

Formula

Block compression stores 4 × 4 pixels per block. BC1 (DXT1): two RGB565 colours + 2-bit indices = 8 bytes (4 bits per pixel). BC2 (DXT3): BC1 colour + explicit 4-bit alpha = 16 bytes. BC3 (DXT5): BC1 colour + interpolated alpha (two end points, 3-bit indices) = 16 bytes. BC4/BC5: one or two such channels.

Colours between the end points are interpolated at ⅓ and ⅔ (or ½ with a transparent fourth colour in 3-colour BC1 blocks). Uncompressed files are decoded from their bit masks (RGB, RGBA, luminance, alpha, 565, 5551, 4444) and the DX10 header's DXGI formats are recognised. Only the top mip level is converted. BC6H (HDR) and BC7 are not supported yet, and the page says so for such files.

Example

A 1024 × 1024 DXT1 texture has 256 × 256 = 65,536 blocks of 8 bytes: 524,288 bytes of top-level pixel data (plus a 128-byte header and smaller mipmaps), against 4,194,304 bytes as raw RGBA — 8 : 1. The same texture in DXT5 takes 1,048,576 bytes, because each block adds 8 bytes of alpha.