Bmp2blit is a command line driven converter that converts 1 bit color bitmap into VES BlitGraphic-data or 4 bit color bitmap into VES MultiBlitGraphics (two or 16 color bmp).
You can also drop a bmp on the icon our just run it and it will convert the file called bitmap.bmp. The parameter -i after the filename inverts the output of a 1-bit bmp.
The color table of the 4 bit color bitmap is interpreted this way, first recommended color in color table and then the interpretation (if they're not the same):
Color 0: black - *background 1: *blue 2: *green 3: *red 4: lt green - *background 5: lt blue - *background 6: lt grey - *background 7: white - *blue (looks white in b&w mode) 8-15: Treated as background
The reason for choosing this particular color table is because that's the result when converting a Channel F emulation screen snapshot in MESS from a 24 bit color png into a 16 color version...
If you use the included test-picture.bmp you'll get the proper palette when drawing.
The blit or multiblit picture is centered on screen with its coordinates if the bmp is smaller than the visible screen area (102x58).