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WoW:BLP file: Difference between revisions

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WoW:BLP file (source)

Revision as of 02:26, 10 October 2010

2,771 bytes added ,  10 October 2010
→‎Sample Files: Found two new strange textures.
(It's bgra, not argb)
(→‎Sample Files: Found two new strange textures.)
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   uint32_t  type;              // Texture type: 0 = JPG, 1 = S3TC
   uint32_t  type;              // Texture type: 0 = JPG, 1 = S3TC
   uint8_t    compression;        // Compression mode: 1 = raw, 2 = DXTC
   uint8_t    compression;        // Compression mode: 1 = raw, 2 = DXTC
   uint8_t    alpha_bits;        // 0, 1, or 8
   uint8_t    alpha_bits;        // 0, 1, 4, or 8
   uint8_t    alpha_type;        // 0, 1, 7 or 8
   uint8_t    alpha_type;        // 0, 1, 7, or 8
   uint8_t    has_mips;          // 0 = no mips levels, 1 = has mips (number of levels determined by image size)
   uint8_t    has_mips;          // 0 = no mips levels, 1 = has mips (number of levels determined by image size)
   uint32_t  width;              // Image width in pixels
   uint32_t  width;              // Image width in pixels
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=== RAW compression ===
=== RAW compression ===
If the <tt>compression</tt> flag is 1, each mipmap is stored as an array of 8-bit values, one per pixel, left to right, top to bottom. Each value is an index to the palette. This is by far the simplest format.
If <tt>compression</tt> is set to 1, each mipmap is stored as an array of 8-bit values, one per pixel, left to right, top to bottom. Each value is an index to the palette.


=== DXT1 compression ===
If <tt>alpha-depth</tt> is greater than 0, an alpha channel will immediately follow the image data, and comes in 1, 4, and 8 bit varieties. The 1 and 4 bit versions have multiple values packed into a single byte, with the least significant bit belonging to the first packed value.
If the <tt>compression</tt> flag is 2, all mipmaps are stored using one of DXT1, DXT3, or DXT5. DXT1 offers either no alpha or 1-bit alpha, and so if the <tt>alpha_bits</tt> value is 0 or 1, the mipmap data will be stored as DXT1.  See [[Wikipedia:S3TC|Wikipedia's entry on DXT compression]] for the technical details.


=== DXT3 compression ===
With the <tt>compression</tt> set to 3, each mipmap contains raw color data. There is only one known image using this format, and had 32 bit BGRA pixels with <tt>alpha-depth</tt> set to 8. One might infer that with <tt>alpha-depth</tt> set to 0 the image would use 24 bit BGR pixels, but no such example exists.
If the <tt>alpha_bits</tt> value is 8, the mipmap data may be in either a DXT3 or DXT5 format. DXT3 alpha data is stored as 4 bits per pixel; DXT3 is identified by an <tt>alpha_type</tt> value of 0, 1, or 8. Again, see [[Wikipedia:S3TC|Wikipedia's entry on DXT compression]] for the technical details.


=== DXT5 compression ===
=== DXTn compression ===
If the <tt>alpha_type</tt> value is 7, the mipmap data is in DXT5 format. This format was first used for Burning Crusade images. [[Wikipedia:S3TC|Wikipedia's entry on DXT compression]] has the goods again.


=== DXT2 and DXT4 ===
If <tt>compression</tt> is set to 2, each mipmap is composed of 4×4 blocks of pixels. The blocks and the pixels within each block are ordered from left to right, top to bottom.
DXT2 and DXT4 are identical to DXT3 and DXT5, respectively, save that pixel data winds up being premultiplied by alpha — that is, each RGBA pixel is not represented by (r, g, b, a) but instead by (ar, ag, ab, a) where all values are normalised to lie between 0 and 1. ''World of Warcraft'' does not use these formats.
 
See [[Wikipedia:S3TC|Wikipedia's entry on DXT compression]] for the technical details.
 
==== DXT1 ====
 
If <tt>alpha_bits</tt> is set to 0, DXT1 compression is used.
 
Each block is 64 bits and begins with two 16 bit values, and are used to derived a 4 color palette.
 
The values are interpreted as 565 RGB colors, with the least significant bits corresponding to blue, to create the first two colors in the palette.
 
If the first value is less than or equal to the second, the final entry of the palette is reserved for black.
 
The remaining colors are created by interpolating between the first two colors in the palette.
 
The remaining 32 bits are 16 2-bit values acting as a lookups to specify the colors in the block.
 
==== DXT1a ====
 
If <tt>alpha_bits</tt> is set to 1, DXT1a compression is used.
 
Each block is 64 bits and is identical to DXT1, except that transparent is reserved in the palette instead of black.
 
==== DXT3 ====
 
If <tt>alpha_bits</tt> is set to 4 or 8, and <tt>alpha_type</tt> is 0, 1, or 8, then DXT3 compression is used.
 
Each block is 128 bits and begins identically to DXT1, except that no special color is reserved in the palette.
 
It is followed by 16 4-bit values corresponding to the alpha values for each of the pixels in the block.
 
==== DXT5 ====
 
If <tt>alpha_type</tt> is 7, then DXT5 compression is used. This format was first used for Burning Crusade images.
 
Each block is 128 bits and begins with two 8-bit values to create an 8 element lookup table for alpha values.
 
The first two elements in the lookup table are copies of those values.
 
If the first value is less than or equal to the second, the final two entries of the lookup table are reserved for transparent and opaque.
 
The remaining entries are created by interpolating between the first two entries in the lookup table.
 
The next 48 bits make up 16 3-bit values acting as lookups specifying the alpha values for each of the pixels in the block.
 
The remaining 64 bits are identical to DXT1, except that no special color is reserved in the palette.
 
==== DXT2 and DXT4 ====
 
DXT2 and DXT4 are identical to DXT3 and DXT5, respectively, save that pixel data winds up being premultiplied by alpha -- that is, each RGBA pixel is not represented by (r, g, b, a) but instead by (ar, ag, ab, a) where all values are normalised to lie between 0 and 1. World of Warcraft does not use these formats.  


=== Sample Files ===
=== Sample Files ===
Below is a list of BLP files, each with some unique characteristic.
{| class="darktable"
{| class="darktable"
! File !! Encoding
! File !! Encoding !! Features
|-
| GLUES\LoadingBar\Loading-BarGlow.blp || RAW1 || No alpha
|-
| Interface\CURSOR\Attack.blp || RAW1 || 1-bit alpha
|-
|-
| GLUES\LoadingBar\Loading-BarGlow.blp || RAW
| Interface\CURSOR\Buy.blp || RAW1 || 8-bit alpha
|-
| Icons\Trade_Alchemy.blp || DXT1 || No alpha
|-
| AuctionFrame\BuyoutIcon.blp || DXT1 || 1-bit alpha
|-
| Icons\INV_Fishingpole_02.blp || DXT3 || 4-bit alpha
|-
| Icons\Ability_Rogue_Shadowstep.blp || DXT5 || 8-bit alpha
|-
| BUTTONS\UI-PaidCharacterCustomization-Button.blp || RAW3 || BGRA color
|}
 
The following files require an MPQ viewer to access, as they aren't exposed by Blizzard's [http://us.blizzard.com/support/article.xml?locale=en_US&articleId=21466 AddOn Kit].
 
{| class="darktable"
! File !! Encoding !! Features
|-
|-
| Icons\Trade_Alchemy.blp || DXT1
| Character\Tauren\Female\TAURENFEMALESKIN00_01_EXTRA.blp || RAW1 || 4-bit alpha
|-
|-
| AuctionFrame\BuyoutIcon.blp || DXT1a
| Environments\Stars\HellFireSkyNebula03.blp || DXT5 || No alpha
|-
|-
| Icons\INV_Fishingpole_02.blp || DXT3
| Textures\SunGlare.blp || RAW3 || alpha_bits=136
|-
|-
| Icons\Ability_Rogue_Shadowstep.blp || DXT5
| TILESET\Terrain Cube Maps\oilslickenvA.blp || RAW3 || alpha_bits=1, width=768
|}
|}


=== Conversion Tools ===
=== Conversion Tools ===
There exist BLP tools to convert both from and to the BLP format. They can be found in the UI Authors resource list: http://www.wowwiki.com/UI_FAQ/AddOn_Author_Resources#Resources
There exist BLP tools to convert both from and to the BLP format. They can be found in the UI Authors resource list: http://www.wowwiki.com/UI_FAQ/AddOn_Author_Resources#Resources
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