A HTC splashscreen is an image used on HTC Android-based phones on startup. It is in a raster graphic format known as "NB" (apparently unrelated to the Mathematica notebook format). While a BMP-to-NB converter program exists which saves the image files in a .nb extension, the HTC actually uses them with a .img extension, contained within a ZIP file (named
PH39IMG.zip) along with a
android-info.txt file giving some metadata.
This is a sample android-info-txt (downloadable here); apparently you have to duplicate this exactly for the splashscreen to work:
hbootpreupdate:13 modelid: PH3910000 cidnum: CWS__001 mainver: 3.26.502.56 hbootpreupdate:12 DelCache:1