[Oberon] FPGA - Screen.Mod

[Tomas Kral]

Hi,

I am trying to revive an old post. Getting Oberon in colour, there is
now a need for `Screen.Grab' handling 4-bit framebuffer. So you may
guess what I struggle with at the moment :-)

Before duplicating the effort, anyone has coded already?

Reading BMP specs may help, but is there a nice small 4-bit indexed
bitmap somewhere, so I could correctly populate the header, colour
table, depth, etc? As my tries so far usually end up in oversized
colour table, invalid BMP format etc.

Still not sure what to do with pixel data. The docs says
 
1-bit (Monochrome Bitmap) "done and works"

Each byte of data represents 8 pixels. The most significant bit maps to
the left most pixel in the group of eight. Any unused bits are set to
zero.

4-bit (16 Color Bitmap) "to do"

Each byte of data represents 2 pixels. The most significant nibble maps
to the left most pixel in the group of two. Any unused nibble is set to
zero.

Many thanks.

-- 
Tomas Kral <thomas.kral at email.cz>