# HackBGRT
HackBGRT is intended as a boot logo changer for UEFI-based Windows systems.
## Summary
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 permanently, 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 Secure Boot is disabled, unless you know how to sign EFI applications.
### Windows installation
* Get the latest release from the Releases page.
* Start `setup.exe` and follow the instructions.
* You may need to manually disable Secure Boot and then retry.
* The installer will launch Notepad for modifying the configuration.
* If you need only one custom image, the defaults are fine.
* Otherwise, check out the examples in the configuration file.
* The installer will launch Paint for creating the image(s).
* You can create multiple images by using Save As.
* Be sure to always use the 24-bit BMP/DIB format.
* If Windows later restores the original boot loader, just reinstall.
* If you wish to change the image or other configuration, just reinstall.
### Multi-boot configurations
If you only need HackBGRT for Windows:
* Extract the latest release 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`.
If you need it for other systems as well:
* Extract the latest release to `[EFI System Partition]\EFI\HackBGRT\`.
* Set `boot=\EFI\your-actual-boot-loader.efi` in `config.txt`.
* Set `\EFI\HackBGRT\bootx64.efi` as your default boot loader with `efibootmgr` or some other EFI boot manager tool.
On 32-bit machines, use `bootia32.efi` instead of `bootx64.efi`.
## 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.
## Recovery
If something breaks and you can't boot to Windows, you have the following options:
* Windows installation (or recovery) media can fix boot issues.
* You can copy `[EFI System Partition]\EFI\HackBGRT\bootmgfw-original.efi` into `[EFI System Partition]\EFI\Microsoft\Boot\bootmgfw.efi` by some other means such as Linux or Windows command prompt.
## Building
* Compiler: GCC targeting w64-mingw32
* Compiler flags: see Makefile
* Libraries: gnu-efi
