Difference between revisions of "IMG archive"
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Revision as of 00:54, 21 January 2009
GTA's most commonly used archive files are known by the extension .img. They have a very simple format and currently exist in multiple versions.
Contents
Structure
Version 1 - GTA III & VC
Version 1 archives, used in GTA III and Vice City, are actually split up into two files: the content directory (.dir) and the actual archive (.img).
The directory is a list of files, each with name, offset and size of the file. The values for offset and size have to be multiplied by 2048, since files are aligned to 2 KB boundaries. This means that even a file with only 123 byte content will take up 2 KB in the archive. Files are stored (usually) unsorted, uncompressed and linear (no directory tree).
First you have to find out the number of entries (n).
Just divide the filesize of the .dir file by 32 and you will get it.
There is no Header, like in V2 (San Andreas) Files!
Entry: (repeated n times)
4 byte - DWORD - offset of file inside archive (in blocks) 4 byte - DWORD - size of file (in blocks) 24 byte - CHAR[24] - name of file
The .img file itself has no special structure or header, just all the files in 2 KB blocks.
Version 2 - GTA SA
Version 2 archives, introduced with GTA San Andreas, combine .dir and .img files into one .img file. The directory has the same format as in version 1, but is located at the beginning of the archive. Files are again aligned to 2 KB boundaries. File offsets are relative to the start of the whole archive, not to the end of the file list.
Header:
4 byte - CHAR[4] - FourCC, always "VER2" 4 byte - DWORD - number of entries (n)
Entry: (repeated n times)
4 byte - DWORD - offset of file inside archive (in blocks) 4 byte - DWORD - size of file (in blocks) 24 byte - CHAR[24] - name of file
A major drawback of this format is the complicated extendability. If you have to add many files, it might happen that you run out of space for the directory, and have to move the first file(s) to the end.
Version 3 - GTA IV
GTA IV introduced yet another .img file format. Not only the format is new, also there can be encrypted archives. The internal IMG parser of the game works with 2 kb buffers, which means that the 2 kb bounds from earlier versions (blocks) are still present.
IMG Header
The header of an unencrypted file always has a size of 20 bytes.
4 byte - DWORD - Identifier (0xA94E2A52 if the archive is not encrypted) 4 byte - DWORD - Version (always 3, if not the format would be differ) 4 byte - DWORD - Number of Items 4 byte - DWORD - Table Size (in bytes) 2 byte - WORD - Size of Table Items (needs to be always 0x10) 2 byte - WORD - Unknown
IMG Table
The table holds information about the items. Each item header has a size of 16 bytes .
4 byte - DWORD - Itemsize (in bytes) 4 byte - DWORD - Resource type 4 byte - DWORD - Offset (in blocks) 2 byte - WORD - Used Blocks 2 byte - WORD - Padding
Item Names' length will be calculate as :
Table Size - (Number of Items * Item Size)
Next that string will be split by '\x0'
A ressource type is identified by the 4b DWORD value:
- 0x01: Generic
- 0x08: Texture archive
- 0x20: Bounds
- 0x6E: Model file
- 0x24: xpfl
