Techwiki:Win32k/ENGBRUSH

The engbrush is used as GDI's brush realization. It's Tag is 'Gebr'

typedef struct _ENGBRUSH
{
  DWORD dwUnknown00; // 000 00000000 
  ULONG cjSize;      // 004 00000144 length of the allocation
  DWORD dwUnknown08; // 008 00000000 
  DWORD dwUnknown0c; // 0c0 00000000
  DWORD dwUnknown10; // 010 0000000c 
  SIZEL sizl;        // 014 00000008 00000008 
  DWORD dwUnknown1c; // 01C 00000018 flags?
  PBYTE pjBits;      // 020 e13fabf8 
  DWORD dwUnknown24; // 024 00000000 
  DWORD dwUnknown28; // 028 00000000 
  DWORD dwUnknown2c; // 02C 00000000
  DWORD dwUnknown30; // 030 00000000 
  DWORD dwUnknown34; // 034 00000000 
  DWORD dwUnknown38; // 038 00000000 
  DWORD dwUnknown3c; // 03C 00000004 == EBRUSHOBJ:ulDCPalTime?
  BYTE aj[];
} ENDBRUSH, *PENGBRUSH;

cjSize

The size of the allocation in bytes, including the header and the bitmap bits.

sizl

Size of the pattern bitmap.

pjBits

Pointer to the bits (first pattern, then mask)