When booting on a UEFI-based computer, Windows may show a vendor-defined logo which is stored on the UEFI firmware in a section called Boot Graphics Resource Table (BGRT). It's usually very difficult to change the image permamently, but a custom UEFI application may be used to overwrite it during the boot. HackBGRT does exactly that.

Usage

Important: If you mess up the installation, your system may become unbootable! Create a rescue disk before use. This software comes with no warranty. Use at your own risk.

Make sure that your computer is booting with UEFI.
Make sure that you have a 64-bit x86-64 processor.
Make sure that Secure Boot is disabled, or learn to sign EFI applications.
Simple Windows installation:
- Get at least these files: bootx64.efi, config.txt, install.bat, splash.bmp.
- Run Command Prompt as Administrator.
- Run install.bat from the Command Prompt.
  - The installer will launch Paint for creating the image(s).
  - The installer will launch Notepad for modifying the configuration.
- If Windows later reinstalls the original boot loader, run install.bat again.
Installation for Windows with another boot loader (e.g. GRUB):
- Copy the mentioned files to [EFI System Partition]\EFI\HackBGRT\.
- Set boot=\EFI\Microsoft\Boot\bootmgfw.efi in config.txt.
- Point your boot loader to \EFI\HackBGRT\bootx64.efi.
Installation for all operating systems:
- Copy the mentioned files to [EFI System Partition]\EFI\HackBGRT\.
- Set boot= to your preferred boot loader in config.txt.
- Set \EFI\HackBGRT\bootx64.efi as your default boot loader with efibootmgr or some other EFI boot manager tool.

Configuration

The configuration options are described in config.txt, which should be stored in [EFI System Partition]\EFI\HackBGRT\config.txt.

Images

The image path can be changed in the configuration file. The default path is [EFI System Partition]\EFI\HackBGRT\splash.bmp.

The image must be a 24-bit BMP file with a 54-byte header. That's a TrueColor BMP3 in Imagemagick, or 24-bit BMP/DIB in Microsoft Paint.

Multiple images may be specified, in which case one is picked at random.

Building

Compiler: GCC targeting w64-mingw32
Compiler flags: see Makefile
Libraries: gnu-efi