BLP Format Guide

Available Conversions

Convert to BLP

About BLP Format

BLP (Blizzard Picture) is a proprietary texture file format developed by Blizzard Entertainment for use in their video game engines. The format was designed specifically to store texture data optimized for real-time rendering in games such as World of Warcraft, Warcraft III: Reign of Chaos, Warcraft III: The Frozen Throne, StarCraft, and other titles built on Blizzard's game engines. BLP files store image data in a format that can be efficiently loaded into GPU memory during gameplay, supporting both JPEG-compressed and palettized pixel data with optional DXT (S3 Texture Compression) encoding. The format includes built-in mipmap support, storing pre-generated downscaled versions of textures that the game engine uses to render objects at different distances, reducing aliasing artifacts and improving rendering performance. BLP files support alpha channel transparency, which is essential for game textures such as foliage, particle effects, UI elements, and character hair that require translucent or cutout regions. The format exists in two major versions: BLP1, used in Warcraft III and earlier titles, and BLP2, used in World of Warcraft and later games, with each version having different internal structure and compression options.

History of BLP

The BLP format was created by Blizzard Entertainment in the early 2000s as a custom texture solution for their game engines. The first version, BLP1, debuted with Warcraft III: Reign of Chaos in 2002, replacing the general-purpose image formats that were common in earlier game development with a purpose-built format optimized for Blizzard's rendering pipeline. BLP1 supported two compression modes: JPEG-based compression for photographic textures and palettized (indexed color) storage for simpler graphics with fewer colors. When Blizzard began developing World of Warcraft, which launched in November 2004, they created BLP2, an enhanced version of the format that added support for DXT1, DXT3, and DXT5 GPU-compressed texture formats. This was critical for World of Warcraft, which needed to load thousands of textures into limited GPU memory as players explored the massive game world. BLP2 became the standard texture format across Blizzard's games for over a decade. The format gained significant attention outside of Blizzard's development team through the game modding community. Warcraft III had a thriving modding scene with tools like the World Editor, and modders needed to create custom BLP textures for their maps, models, and UI elements. Community-developed tools such as BLP Lab, BLP Converter, and Warcraft III Viewer emerged to allow modders to convert between BLP and standard image formats. The World of Warcraft addon and private server communities further expanded interest in BLP, with data miners and modders extracting and modifying game textures for custom interfaces, texture packs, and model modifications. Pillow, the primary Python image processing library, added native BLP reading support, enabling programmatic access to BLP texture data without requiring specialized game modding tools.

Key Features and Uses

BLP files are structured with a header containing format version, compression type, alpha bit depth, image dimensions, and offsets to mipmap data. BLP1 files begin with a "BLP1" magic number and support JPEG compression (type 0) or palettized storage (type 1) with a 256-color palette. BLP2 files use a "BLP2" magic number and extend the compression options to include DXT1 (opaque or 1-bit alpha), DXT3 (explicit 4-bit alpha), and DXT5 (interpolated alpha) GPU compression alongside the original palettized and uncompressed modes. Both versions store mipmaps as separate data blocks within the file, with up to 16 mipmap levels supported. The format enforces power-of-two dimensions (such as 256x256, 512x512, or 1024x1024) to ensure compatibility with GPU texture sampling hardware. Alpha channels in BLP files can be stored at 0-bit (fully opaque), 1-bit (binary transparency), 4-bit (16 alpha levels), or 8-bit (full alpha gradient) depth depending on the compression mode and the texture's transparency requirements. DXT-compressed BLP textures remain compressed in GPU memory, providing significant VRAM savings: DXT1 uses 4 bits per pixel compared to 32 bits for uncompressed RGBA, an 8:1 compression ratio. For game modders, BLP is the required format for custom textures in Warcraft III maps, World of Warcraft interface addons, and model replacements in Blizzard's games.

Common Applications

BLP files are used primarily within Blizzard Entertainment's game ecosystem. In World of Warcraft, every texture visible in the game world -- terrain, character skins, armor, weapons, spell effects, UI elements, loading screens, and environmental objects -- is stored as a BLP file within the game's data archives (MPQ and later CASC containers). Warcraft III uses BLP textures for all in-game graphics including unit models, building textures, terrain tiles, and the game's user interface. The game modding community is the largest external user of BLP format, with thousands of modders creating custom textures for Warcraft III custom maps, World of Warcraft private servers, and cosmetic modifications. Tools like MPQ Editor, CASCExplorer, and WoW Model Viewer allow modders to extract BLP textures from game archives for reference or modification. Game artists working on Blizzard titles or mods typically create textures in standard formats like PSD, PNG, or TGA using Photoshop or other image editors, then convert them to BLP using specialized tools before importing into the game engine. Fan art communities use BLP conversion to create texture packs that replace default game visuals with custom artwork. Data mining communities extract and convert BLP textures to standard formats like PNG or JPG to preview unreleased game content, document game assets, or create wikis and databases of in-game items and characters. Converting BLP to widely supported formats is essential for viewing, editing, sharing, or archiving game textures outside of Blizzard's proprietary tools and game engines.

Advantages and Disadvantages