flat assembler - Vesa Mode Colors???

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newport

Joined: 08 Jun 2012
Posts: 86
Location: Kentucky, USA

newport 07 Apr 2016, 18:49

I have currently set up Vesa using the code below . However, this particular mode has a supposed 64k color palette. The problem is, I cannot figure out how to code a specific color. For example.. plotting a pixel with 0xFFFFFF produces a white pixel, 0x000000 produces a black pixel, but 0x00FF00 which should be green, produces a dark yellow color. Am I incorrect in correlating the color scheme to a standard rgb color palette? How can I determine the correct color I want???

Code:

        mov  ax, 4f01h
        mov  bx, 4114h  ;800x600 - 64k - 16-bit (5:6:5)
        mov  di, Mode_Info
        mov  cx, bx
        int  10h
         
        mov  ax, 4f02h
        int  10h

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Last edited by newport on 07 Apr 2016, 19:14; edited 2 times in total

07 Apr 2016, 18:49

newport

Joined: 08 Jun 2012
Posts: 86
Location: Kentucky, USA

newport 07 Apr 2016, 19:03

ok.. as always, i seem to find my answers after posting... lol - this link helped me understand how to convert rgb colors to 5:6:5 colors -

http://www.avrfreaks.net/forum/color-map-ili93401-tft-display

..and excerpt from the page states..

Code:


Pick some colours, for example I like the look of #66FF99 and then convert this 24 bit 8:8:8 value to
5:6:5 or 6:6:6 using the most significant bits. So for this lovely greeney-blue the 66FF99 is:

    R: 0x66 = 0b01100110
    G: 0xFF = 0b11111111
    B: 0x99 = 0b10011001

To convert to 18 bit (6:6:6) just take the top 6 bits of each:

    R: 011001
    G: 111111
    B: 100110

then add them together to make the 18bits

    011001 111111 100110

grouping that in fours:

    01 1001 1111 1110 0110

which in hex is:

    0x19FE6

Doing the same for 16 bit (5:6:5) would be:

    R: 01100
    G: 111111
    B: 10011

which is

    0110 0111 1111 0011

    0x67F3

So "limey green" is 0x19FE6 in 18 bit mode and 0x67F3 in 16 bit mode.

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07 Apr 2016, 19:03

cod3b453

Joined: 25 Aug 2004
Posts: 618

cod3b453 07 Apr 2016, 20:59

The VBE3 standard (http://www.petesqbsite.com/sections/tutorials/tuts/vbe3.pdf) defines the layouts for preset modes but also provides generic RGB field info in the get mode info function (#1), which could help - though to be honest I went straight to 24/32 bit modes for the simplicity Laughing

07 Apr 2016, 20:59

newport

Joined: 08 Jun 2012
Posts: 86
Location: Kentucky, USA

newport 08 Apr 2016, 14:51

i wanted to use 24or 32 bit, but the only vesa modes that would work with my computer are .. 101h, 111h, 114h, and 117h...

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08 Apr 2016, 14:51

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