Let me get it straight

you want to convert the image which is in the video memory to a bmp ?
The game you are talking about is a mode 0xd game (16 colours)
(you know dosbox can make screenshots with ctrll-f5 ? )

Some pointers:
VGA_Draw_4BPP_Line in hardware vga_draw.cpp : draws 16 colours (it does it by writing pallette values).
The pallete itself is set via int10 to the video card in the file hardware/vga_attr.cpp

>> you want to convert the image which is in the video memory to a bmp ?
Nope. I take image from file show it to screen, сonvert it to bmp and so on...
>> The game you are talking about is a mode 0xd game (16 colours)
Yes.
>> you know dosbox can make screenshots with ctrll-f5 ?
Yes i know. But i does not need this. I plan to start remake of this game, capable of playing with original data, so i try to figure out data formats and basic parameters.

>> VGA_Draw_4BPP_Line in hardware vga_draw.cpp : draws 16 colours (it does it by writing pallette values).
>> The pallete itself is set via int10 to the video card in the file hardware/vga_attr.cpp
Ok, thanks. I partially fixed problem with color conversion.

There still is mysterious thing: game palette has entry for white color which sets five of six color bits to 1: 0x1f. When i convert it with my routine it looks like wery bright cyan (because here one red bit missing). When i run game under Dosbox white looks like white. First i thought they reprogrammed videocontroller somehow, but if i add one red component to all colors picture looks worse than before. Can not figure out reasons for that and find solution :-/

Do they change the palette (through int10 or by reprogramming
the DAC or attr regs)? Or does it use the standard pal set up
by the video mode change?
Also what game is it?

> Do they change the palette (through int10 or by reprogramming
the DAC or attr regs)? Or does it use the standard pal set up
by the video mode change?
They change palette through int 10h. Here is palette extracted from the game:

1static Uint8
2dos_color_table[16]=
3{
4  0x00, 0x01, 0x02, 0x03,
5  0x04, 0x05, 0x06, 0x07,
6  0x18, 0x19, 0x1a, 0x1b,
7  0x1c, 0x1d, 0x1e, 0x1f
8};

As you can see top half of palette defines colors without one red bit. The misterious thing here is that colors look correct in dosbox and without emulation. But since my conversion routine expects red here half part of palette in converted pictures lacks red. Low eight colors looks good.
> Also what game is it?
The game in question is Dangerous Dave in tht Haunted Mansion.

You're missing the attr-layer.
Have a look at ega_palette in int10_modes.cpp, the colours of
the games are indices into this table (unless the DAC is changed
of course).

hth

Ok, thanks. this solved problem.

Maybe you want to post your conversion or a link to it some time 😀

> Maybe you want to post your conversion or a link to it some time
Remake is in early stage and does not have web page. I plan to publish it when it will be capable of loading and displaying levels.