.BLP files are texture files used by games made by Blizzard Entertainment. While Blizzard provides an Interface AddOn Kit for extracting the user interface files from the World of Warcraft .MPQs, they do not provide a utility to view the .BLP files contained within. Also, .BLP graphics were used for Warcraft III, and are also stored within .MPQs.

Format

The file starts with a proprietary header, proceeded by the texture data. The texture data are typically stored in DXT1, DXT3, uncompressed or possibly DXT5. It is vital to note that the size of the image is a power of 2.

Converters

Several third party applications exist that can convert .BLP files to .tga files and vice versa. Some of the programs were made for Warcraft III textures, however, and do not work for all Blizzard game textures. These converters have become very vital to the Warcraft III modding community, and have been the doorway to the vast amount of customised skins available for download.

Specification

Note that all types are little-endian.

Only the BLP2 format is shown here; for the BLP1 format, refer to BLP version 1 format specifications

BLP2 Format

Type 1 Encoding 1 AlphaDepth 0 (uncompressed paletted image with no alpha)

Each byte of the image data is an index into Palette which contains the actual RGB value for the pixel. Although the palette entries are 32-bits, the alpha value of each Palette entry may contain garbage and should be discarded.

Type 1 Encoding 1 AlphaDepth 1 (uncompressed paletted image with 1-bit alpha)

This is the same as Type 1 Encoding 1 AlphaDepth 0 except that instantly following the index array is a second image array containing 1-bit alpha values for each pixel. The first byte of the array is for pixels 0 through 7, the second byte for pixels 8 through 15 and so on. Bit 0 of each byte corresponds to the first pixel (leftmost) in the group, bit 7 to the rightmost. A set bit designates the pixel is opaque while a zero bit designates a transparent pixel.

Type 1 Encoding 1 AlphaDepth 8 (uncompressed paletted image with 8-bit alpha)

This is the same as Type 1 Encoding 1 AlphaDepth 0 except that instantly following the index array is a second image array containing the actual 8-bit alpha values for each pixel. This second array starts at BLP2Header.Offset + BLP2Header.Width * BLP2Header.Height.

Type 1 Encoding 2 AlphaDepth 0 (DXT1 no alpha)

The image data are formatted using DXT1 compression with no alpha channel.

Type 1 Encoding 2 AlphaDepth 1 (DXT1 one bit alpha)

The image data are formatted using DXT1 compression with a one-bit alpha channel.

Type 1 Encoding 2 AlphaDepth 8 AlphaEncoding 1(DXT3)

The image data are formatted using DXT3 compression.

Type 1 Encoding 2 AlphaDepth 8 AlphaEncoding 7(DXT5)

The image data are formatted using DXT5 compression.