Helper function for image file loaders.

function Has16BitImageAlpha(NumPixels: LongInt; 
                            Data: PWord): Boolean;

ImagingFormats (at line 154)

Some 15 bit images (targas, bitmaps) may contain 1 bit alpha but there is no indication of it. This function checks all 16 bit(should be X1R5G5B5 or A1R5G5B5 format) pixels and some of them have alpha bit set it returns True, otherwise False.