Ace Combat 7 - Editing DXT5 MREC Textures in GIMP
https://superostrich.xyz/ac7.html#guides
Table of Contents
Creating an Editable Image
Transfering the original Alpha Channel to your edited texture
TL;DR
Creating an Editable Image
- Open the original DDS file, it should appear almost entirely blank

- Click on the Channels tab, Uncheck Alpha
- Click on Layers tab, right-click > New layer from visible
- Click on the Channels tab, Check Alpha

- You will now have an editable layer, proceed to edit as normal in GIMP (you could also edit in other software, and then re-import your changes as a new layer)
- Do not modify the layer that you originally imported (In this example MR2K_00_MREC.dds), you will need it later.
Transfering the original Alpha Channel to your edited texture

- Now that you have made the changes you want to your MREC you need to re-apply the Alpha Channel from the original MREC texture.
- Create a single flattened layer with all your changes. Easiest way is to go to layers tab right-click > new layer from visible
- Make all layers invisible except for one you just created (named Visible or Visible #1)
- Right-click on the original DDS layer (eg. mr2k_00_MREC.dds) > alpha to selection
- Select your flat visible layer (eg. Visible)
- On the menu-bar click select > invert then click edit > clear

- Your image should now look mostly invisible

- Export your flat ‘visible’ layer as a DXT5 DDS file and pack it up!
TL;DR
To transfer the alpha channel from one layer to another;
- Perform an alpha-to-selection on the source layer
- Invert your selection
- Perform a clear (Del) on your destination layer
https://superostrich.xyz/ac7.html#guides