How to decode the Nintendo logo from gameboy?

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眼角桃花
眼角桃花 2021-02-19 06:22

I\'ve tried to decode the following bitmap using the background pallete scheme described at http://imrannazar.com/GameBoy-Emulation-in-JavaScript:-Graphics

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  • 2021-02-19 07:00

    There is no compression or encrytion at all. The logo is binary encoded: 1 is black and 0 is white/green/whatever you want to call the background color of the game boy).

    Simply put the hexadecimal string in the correct order and then convert the hex chars to binary:

    Hexadecimal:

    C 6 C 0 0 0 0 0 0 1 8 0
    E 6 C 0 3 0 0 0 0 1 8 0
    E 6 0 0 7 8 0 0 0 1 8 0
    D 6 D B 3 3 C D 8 F 9 E
    
    D 6 D D B 6 6 E D 9 B 3
    C E D 9 B 7 E C D 9 B 3
    C E D 9 B 6 0 C D 9 B 3
    C 6 D 9 B 3 E C C F 9 E
    

    Binary:

    1100 0110 1100 0000 0000 0000 0000 0000 0000 0001 1000 0000
    1110 0110 1100 0000 0011 0000 0000 0000 0000 0001 1000 0000
    1110 0110 0000 0000 0111 1000 0000 0000 0000 0001 1000 0000
    1101 0110 1101 1011 0011 0011 1100 1101 1000 1111 1001 1110
    1101 0110 1101 1101 1011 0110 0110 1110 1101 1001 1011 0011
    1100 1110 1101 1001 1011 0111 1110 1100 1101 1001 1011 0011
    1100 1110 1101 1001 1011 0110 0000 1100 1101 1001 1011 0011
    1100 0110 1101 1001 1011 0011 1110 1100 1100 1111 1001 1110
    

    There you go. Your Nintendo logo (w/o 0 and spaces):

    11   11 11                             11       
    111  11 11        11                   11       
    111  11          1111                  11       
    11 1 11 11 11 11  11  1111  11 11   11111  1111 
    11 1 11 11 111 11 11 11  11 111 11 11  11 11  11
    11  111 11 11  11 11 111111 11  11 11  11 11  11
    11  111 11 11  11 11 11     11  11 11  11 11  11
    11   11 11 11  11 11  11111 11  11  11111  1111 
    

    Using instead of 1:

    ██   ██ ██                             ██       
    ███  ██ ██        ██                   ██       
    ███  ██          ████                  ██       
    ██ █ ██ ██ ██ ██  ██  ████  ██ ██   █████  ████ 
    ██ █ ██ ██ ███ ██ ██ ██  ██ ███ ██ ██  ██ ██  ██
    ██  ███ ██ ██  ██ ██ ██████ ██  ██ ██  ██ ██  ██
    ██  ███ ██ ██  ██ ██ ██     ██  ██ ██  ██ ██  ██
    ██   ██ ██ ██  ██ ██  █████ ██  ██  █████  ████ 
    
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  • 2021-02-19 07:05

    In addition to the answer by PBurggraf, here is a snippet of my code that I used to check my understanding of it.

    static const uint8_t data[] = {
        0xCE, 0xED, 0x66, 0x66, 0xCC, 0x0D, 0x00, 0x0B, 0x03, 0x73, 0x00, 0x83,
        0x00, 0x0C, 0x00, 0x0D, 0x00, 0x08, 0x11, 0x1F, 0x88, 0x89, 0x00, 0x0E,
        0xDC, 0xCC, 0x6E, 0xE6, 0xDD, 0xDD, 0xD9, 0x99, 0xBB, 0xBB, 0x67, 0x63,
        0x6E, 0x0E, 0xEC, 0xCC, 0xDD, 0xDC, 0x99, 0x9F, 0xBB, 0xB9, 0x33, 0x3E,
    };
    
    for(int y=0; y<8; ++y)
    {
        int i = ((y/2)%2)+(y/4)*24;
        for(int x=0; x<12; ++x,i+=2)
        {
            const uint8_t nibble = (y%2) ? (data[i]&0xF) : (data[i]>>4);
            for(int b=4; b--;) std::cout << (((nibble>>b)&1) ? "*" : " ");
        }
        std::cout << std::endl;
    }
    

    It outputs:

    **   ** **                             **       
    ***  ** **        **                   **       
    ***  **          ****                  **       
    ** * ** ** ** **  **  ****  ** **   *****  **** 
    ** * ** ** *** ** ** **  ** *** ** **  ** **  **
    **  *** ** **  ** ** ****** **  ** **  ** **  **
    **  *** ** **  ** ** **     **  ** **  ** **  **
    **   ** ** **  ** **  ***** **  **  *****  **** 
    

    Hope it helps someone.

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  • 2021-02-19 07:11

    Clarification:

    And there is a kind of enryption/compression on the logo.

    1. You must sort the hexstring (decrypt)
    2. You must draw each bit 4 times (decompress) As pokechu22 said before.
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