Rescomp colour conversion

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matteus
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Rescomp colour conversion

Post by matteus » Fri Mar 16, 2018 9:49 am

I thought I'd post here as I think grand master Stef is busy :)

Does anyone know how rescomp decides upon the colours it uses for conversion?

Does it use standard 9-bit colour RGB values
0, 32, 64, 96, 128, 160, 192, 224, 256

Old incorrect linear levels RGB values
0, 36, 72, 108, 144, 180, 216, 252/255

Or Tiido's Nonlinear levels RGB values
0, 52, 87, 116, 144, 172, 206, 255

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Grind
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Re: Rescomp colour conversion

Post by Grind » Fri Mar 16, 2018 2:10 pm

Looks like it uses the standard.

In tools/rescomp/src/tools.c:

Code: Select all

unsigned short toVDPColor(unsigned char b, unsigned char g, unsigned char r)
{
    // genesis only define on 3 bits (but shifted to 1 left)
    r = (r >> 4) & 0xE;
    g = (g >> 4) & 0xE;
    b = (b >> 4) & 0xE;

    return (r << 0) | (g << 4) | (b << 8);
}

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Sik
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Re: Rescomp colour conversion

Post by Sik » Fri Mar 16, 2018 2:44 pm

Huh... I just did some checks and if you take Tiido's values and leave only the higher three bits (like rescomp does) it actually gives the correct result. Go figure.
Sik is pronounced as "seek", not as "sick".

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TmEE co.(TM)
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Re: Rescomp colour conversion

Post by TmEE co.(TM) » Sat Mar 17, 2018 7:41 am

I just do 255/34 in my tools and it works for linear and the nonlinear ramp too.
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