Image attributes not preserved in extracted textures

Using the 0.0.5 alpha.2 appimage to extract textures from the otr produced by SoH 7.1.0 and the OoT N64 PAL 1.1 rom (sha1sum: cfbb98d392e4a9d39da8285d10cbef3974c2f012), I get a large amount of textures where the alpha channel has been removed, or where the image has been converted to grayscale. The otr produced by SoH appears to be fine as the game plays as expected, so I'm assuming that the issue is in retro's extraction. An example of both cases, along with the the output from Imagemagick's 'identify' for each texture is provided [here](https://drive.google.com/drive/folders/1yk9QUr7m5fNpTe3wvzmJgsWJG_UaAUv7?usp=sharing). The files extracted by retro are suffixed with '_retro' and the reference images were dumped from gliden64 (and correspond with popular texture repacks).

Many textures appear to be fine, with or without alpha channels, so I've been unable to rectify this programmatically in post. I really hope that you can rectify this as it would streamline community asset creation.

Start by reproducing texture extraction with the listed SoH 7.1.0 OTR and PAL 1.1 ROM, then compare extracted files with the linked references and ImageMagick identify output. Trace the extraction path responsible for image channels and color mode. Done means extracted textures preserve the source alpha channels and color information instead of losing alpha or becoming grayscale.

Written by the indexing model from the issue text.