public Set<File> getExternalIconFiles() {
		Set<File> files = new HashSet<>();
		for (IconValue iconValue : iconMap.values()) {
			Icon icon = iconValue.getRawValue();
			if (!(icon instanceof UrlImageIcon urlIcon)) {
				continue;
			}

			String originalPath = urlIcon.getOriginalPath();
			if (!originalPath.startsWith(ResourceManager.EXTERNAL_ICON_PREFIX)) {
				continue;
			}

			URL url = urlIcon.getUrl();
			String filePath = url.getFile();
			if (filePath == null) {
				continue;
			}

			File iconFile = new File(filePath);
			if (iconFile.exists()) {
				files.add(iconFile);
			}
		}
		return files;
	}
Gets the set of icon (.png, .gif) files that are used by IconValues that came from files
versus resources in the classpath. These are the icon files that need to be included when
exporting this set of values to a zip file.
@return the set of icon (.png, .gif) files that are used by IconValues that came from files
versus resources in the classpath
Ghidra/Framework/Gui/src/main/java/generic/theme/GThemeValueMap.java