This program uses java.awt.Graphics2D to generate the background text files used under recovery mode. And thus we don't need to do the manual work by running emulators with different dpi.
java -jar path_to_jar --image_width imageWidth --text_name textName --font_dir fontDirectory --resource_dir resourceDirectory --output_file outputFilename
imageWidth: The number of pixels per line; and the text strings will be wrapped accordingly.textName: The description of the text string, e.g. “recovery_erasing”, “recovery_installing_security”fontDirectory: The directory that contains all the support .ttf | .ttc files, e.g. $OUT/system/fonts/resourceDirectory: The resource directory that contains all the translated strings in xml format, e.g. bootable/recovery/tools/recovery_l10n/res/outputFilename: Path to the generated image.