sharik@wiliki.eng.hawaii.edu (Harikrishnan Sundararaghavan) (04/27/91)
Hello !! I would like to know whether it is possible to show more than 16 colors in 640x350 mode. Will direct video memory access allow me to do this? Thanks, Hari. Harikrishnan Sundararaghavan (Hari),
joe@proto.com (Joe Huffman) (04/29/91)
sharik@wiliki.eng.hawaii.edu (Harikrishnan Sundararaghavan) writes: > I would like to know whether it is possible to show more than >16 colors in 640x350 mode. Will direct video memory access allow me to >do this? Assuming you mean with a true blue EGA board and not a VGA emulating the EGA or a 'Super EGA' board then the answer is that it is POSSIBLE to show up to 64 colors simultaneously, but it isn't easy. You have to look for the horizontal retrace signal and then change the palette on the fly, thus you can show up to 64 colors on the screen simultaneously but you are restricted to only one set of 16 in any horizontal line. This restriction, and it being very cpu intensive, makes it more of a curiosity that a useful coding method. If you are really interested I think I might be able to find the source for a demo of this. -- joe@proto.com
sharik@wiliki.eng.hawaii.edu (Harikrishnan Sundararaghavan) (04/30/91)
In article <1991Apr28.180038.10097@proto.com> joe@proto.com (Joe Huffman) writes: >sharik@wiliki.eng.hawaii.edu (Harikrishnan Sundararaghavan) writes: > >> I would like to know whether it is possible to show more than >>16 colors in 640x350 mode. Will direct video memory access allow me to >>do this? > >Assuming you mean with a true blue EGA board and not a VGA emulating the EGA >or a 'Super EGA' board then the answer is that it is POSSIBLE to show up to >64 colors simultaneously, but it isn't easy. You have to look for the >-- >joe@proto.com Say it is a VGA emulating EGA ( or VGA itself ) Is it possible to show more than 16 colors in the hi-resolution modes. Hari. Harikrishnan Sundararaghavan (Hari),
joe@proto.com (Joe Huffman) (04/30/91)
sharik@wiliki.eng.hawaii.edu (Harikrishnan Sundararaghavan) writes: >Say it is a VGA emulating EGA ( or VGA itself ) Is it possible to show more >than 16 colors in the hi-resolution modes. Some boards have modes of operation that allow this quite easily. Others do not (assuming hi-resolution means > 320 x 200). On the ones that do not it can probably still be done 'the hard way'. But I feel that it will probably result in unsatisfactory results. Here is a program that will display 64 simulataneous colors in mode 3 (80 x 25 text mode0) I believe the same technique can be used in most of the graphics modes but note the jitter on the first line of every horizontal band when the palette is changed. Also note that one whole line is black between bands... --- begin 644 egapalet.com MZP$B_+@# ,T0N "XCL I_[#;MQDHY+,(N0H \ZO^Q/[+=?7^SW7MBCX" ;K: M [A ([8^RCDLP'Z[*@(=/KLJ AU^^S0Z'/[_LMT!^S0Z'+[Z_"Y" "RP(C@ G) ?NB.#N_L3B]+ @[K+:B/N _$!UTXL.&@ [#AP =+FX P#-$,T@ end -- joe@proto.com