.tga File Extension (BIMAGE)

This page is not yet complete. WIP.

Despite the name, the ".tga" files used in Doom Eternal are not actually .tga (targa) images. They are actually "BIM" (or .bimage) files of various formats.

These files are stored in two parts. The file header is embedded in Doom Eternal's .resources files. The body of the file is embedded in Doom Eternal's .streamdb files.

File Signature

Doom Eternal ".tga" files can be identified by the first 3 bytes of the file header, which is always 0x42 0x49 0x4D or "BIM", short for "bimage" or "binary image".

"Header" Structure

The basic file header structure is a 63-byte HEADER struct, followed by a variable number of 36-byte MIPMAP structs.

struct FILE_HEADER
{
    HEADER header;
    MIPMAP mipmap[];				// Flexible array member, length varies with header.MipCount;
};

The HEADER struct is a 63-byte sequence described as follows:

struct HEADER 
{		
	char Signature[3];				// "BIM"
    byte Version;					// 0x15
	int TextureType; 				// enum textureType_t
	int TextureMaterialKind;		// enum textureMaterialKind_t
	int PixelWidth;					// image width in pixels
	int PixelHeight;				// image height in pixels
	int Depth; 
    int MipCount; 					// "numLevels"determines in# IDAof MIPMAP structs to follow
	__int64 MipLevel;				
	float unkFloat1; 				// usually 1.0, purpose unknown
	bool boolIsEnvironmentMap;
	int TextureFormat;				// enum textureFormat_t
	int Always7;					// unknown, but literally always 7
	int nullPadding;
	short AtlasPadding;
	bool boolIsStreamed;			// 1 if file is located in streamDB, 0 if not
	bool unkBool;
	bool boolNoMips;
	bool boolFFTBloom;
	int StreamDBMipCount; 			// usually same number of mips stored in streamdb
};

The MIPMAP struct is a 36-byte sequence described as follows. The MIPMAP structure is repeated n times, where n  is equal to HEADER.MipCount above.

struct MIPMAP
{
	__int64 MipLevel;				// Starts at 0, increments each time it repeats
	int MipPixelWidth;				// Original PixelWidth reduced by 50% for each MipLevel
	int MipPixelHeight;				// Original PixelHeight reduced by 50% for each MipLevel
	int UnknownFlagA;
	int DecompressedSize;			// Decompressed size in bytes
	int FlagIsCompressed;			// 1 if the texture is compressed, 0 if not
	int CompressedSize;				// Compressed size in bytes
	int CumulativeSizeStreamDB;		
};