Tiny bitmap font rendering

nanofont.cpp

// c++ -o nanofont nanofont.cpp && time ./nanofont /tmp/font.png && open /tmp/font.png
#include <cstdio>
#include <vector>

// Glyphs from http://font.gohu.org/ (8x14 version, most common ascii characters only)
// Arguments are the ascii character to print, and x and y positions within the glyph.
// This function must be paired with some mechanism to plot pixels (sample below).
inline bool glyph_pixel(unsigned int c, unsigned int x, unsigned int y) {
    c -= 33; x--; if (c > 93 || x > 6 || y > 13) return 0; int i = 98 * c + 7 * y + x;
    return (("0@P01248@00120000P49B0000000000000:DXlW2UoDX@10008@h;IR4n@R<Y?48000PYDF"
    "PP011J:U1000<T8QQQDAR4a50000@P012000000000000222448@P024@010028P0148@PP011100000"
    "ABELDU410000000048@l7124000000000000000H`01100000000n10000000000000000006<0000@P"
    "P011224488@00000`CXHY:=:D8?0000004<DT01248@000000l4:444444h700000`C8@Ph02D8?0000"
    "008HX89b?8@P000000n58`7@P05b300000`CP0O25:D8?00000POPP0112248000000l4:D8?Q25b300"
    "000`CX@Ql1244700000000H`0000<H00000000`P1000H`0110000044444@014@0000000n100PO000"
    "0000004@014@@@@@0000h948@@@@00120000`G`l5;F\\Lf0n100000l4:DXOQ25:400000hCX@Qn4:D"
    "X?000000?Q248@P0Ql000000N49DX@Q25i100000hGP01N48@PO00000PO124hAP012000000l4:@PLQ"
    "25b3000008DX@Qn5:DX@000000748@P0124L00000001248@P25b3000008DT456D8AT@00000P01248"
    "@P01n10000017G=IbP1364000008dXAU:U:E\\H000000?Q25:DX@Ql000000n4:DX?1248000000`CX"
    "@Q2U:E4GP0000P?Q25jCR8Q2100000l4:@0?P05b300000l71248@P01200000P@Q25:DX@Ql0000002"
    "5:D89BT`P1000004<HbT9[:BT800000P@QT8QQ49Q210000013:B4548@P000000h7888888@PO00000"
    "7248@P01248`10P0148P0148P0148000h01248@P0124>000015A000000000000000000000000h?00"
    "04@010000000000000000l0bGX@aL10000124XcX@Q25j300000000?Q248@8?000008@Pl5:DX@aL10"
    "000000`CX@o24`70000`AP01N48@P0100000000l5:DX@aL12T70124XcX@Q25:40000@P0P348@P01>"
    "00000240HP01248@P0a101248@T47B4940000HP01248@P01L00000000oBV<IbT910000000hCX@Q25"
    ":400000000?Q25:D8?00000000j<:DX@Qn48@00000`GX@Q25c58@P0000P>S248@P000000000l48P7"
    "@Pn0000048@`31248@030000000P@Q25:D<G0000000025:T49<H000000004<HbTE5920000000P@QT"
    "`@BX@0000000025:DX@aL12T70000h744444h70000PS01248>P0124`1001248@P01248@P0007@P01"
    "24`@P01R30000000S9S10000000"[i / 6] - '0') >> (i % 6)) & 1;
}

// Example usage:
struct Img {
    Img(unsigned w, unsigned h) : w(w), h(h), p(w * h, 0) {}

    // draw characters one at a time
    void draw_string(const char* msg, int bx, int by) {
        for (int lx = bx; *msg;
                 lx = *msg == '\n' ? bx : lx +  8,
                 by = *msg != '\n' ? by : by + 14,
                 msg++)
        for (int y = 0; y < 14; y++)
        for (int x = 0; x < 8 ; x++)
            if (glyph_pixel(*msg, x, y))
                plot(lx + x, by + y);
    }

    void plot(unsigned x, unsigned y) {
        if (x < w && y < h) p[y * w + x] = 0xff;
    }

    unsigned w, h; std::vector<unsigned char> p;
};

// nanopng: https://gist.github.com/fpsunflower/a79b06e92968465397d4
// tweaked for single channel output
struct Png {
    FILE*f; unsigned int tab[256], crc; ~Png() { fclose(f); }
    Png(const char* fn, int w, int h, const unsigned char* c) {
        crc=0x575e51f5;unsigned char d[]={137,80,78,71,13,
        10,26,10,0,0,0,13,73,72,68,82,73,68,65,84,120,1,0,
        0,0,73,69,78,68,174,66,96,130};/*chunk headers*/
        for (int i=0;i<256;i++)/*precompute crc tables*/
            for (unsigned int j=8,&v=tab[i]=i;j--;)
                v=(v>>1)^(0xedb88320u&(~(v&1)+1));
        fwrite(d,1,16,f=fopen(fn,"w")); /*write IHDR+IDAT*/
        *this>>w>>h<<8<<2<<0<<0<<0;int a=1,b=0;/*adler-32*/
        *this>>~crc>>(h*(w*3+6)+6);int len=w*3+1;/*nbytes*/
        fwrite(d+16,1,6,f);crc=0x13e5812d;
        for (;h--;) {/*DEFLATE raw block*/
            *this<<!h<<len<<(len>>8)<<~len<<(~len>>8);
            /*filter=0*/*this <<0;/*adler(0)*/b=(a+b)%65521;
            for (int x=w,v;x--;){ /*write & checksum*/
                v=*c++;*this<<v;a=(a+v)%65521;b=(a+b)%65521;
                       *this<<v;a=(a+v)%65521;b=(a+b)%65521;
                       *this<<v;a=(a+v)%65521;b=(a+b)%65521;
            }
        }
        *this>>((b<<16)|a);*this>>~crc;fwrite(d+22,1,12,f);
    }
    Png& operator<<(int b){crc=(crc>>8)^tab[(crc^fputc(b,f))&255];return *this;}
    Png& operator>>(unsigned int v) {return *this<<(v>>24)<<(v>>16)<<(v>>8)<<v;}
};

int main(int argc, const char** argv) {
    Img img(560, 128); img.draw_string(
        "| #include <stdio.h>\n"
        "|\n"
        "|\n"
        "| // The quick brown fox jumps over the lazy dog.\n"
        "| int main(int argc, const char* argv[]) {\n"
        "|    printf(\"Hello World!\\n\");\n"
        "|    return 0;\n"
        "| }\n"
        "|", 144, 0);
    for (char s[] = { 0, 0 }; *s < 127; s[0]++)
        img.draw_string(s, 8 * (*s % 16), 14 * (*s / 16));
    Png(argc < 2 ? "/tmp/test.png" : argv[1], img.w, img.h, &img.p[0]);
}