FXX and WXX are the image format for high resolution sprites in the Dark Forces Remaster. They replace FMEs and WAXes respectively. FXX and WXX are actually the same format, differing only in file extension.
FXX/WXX are true colour with an alpha channel.
FXX/WXX sprites will be loaded in place of a classic sprite if they have the same name (eg. hello.WAX, hello.WXX). Their image(s) must be exactly double the dimensions of the image(s) in the FME or WAX they are substituting for.
File format
FXX/WXX files contain minimal metadata. The game obtains key data (widths and heights of images, offsets, animation sequences, frame rates, etc.) from the corresponding FME or WAX.
Header
The FXX/WXX header is as follows.
FXX/WXX header
{
NumImages int32
ImageSizes int32[NumImages] // The values are the number of pixels in each image
}
FXXs will only have one image, WXXs may have one or more corresponding to the number of images in the base WAX.