hos/fontgen/fontgen.c

#include <stdlib.h>
#include <stdint.h>
#include <ft2build.h>
#include <stdio.h>
#include FT_FREETYPE_H
#include <string.h>
#include <strings.h>
#include <ctype.h>

#define N_CHARS 128

#define round_up_26_6(val) (((val) + 63) >> 6u)

int max_advance;
int max_top = -9999;
int min_bottom = 9999;
int line_height;
int baseline_offset;

typedef struct {
    int width;
    int height;
    int top;
    int left;
    uint8_t * bitmap;
} char_info_t;

static char_info_t char_infos[N_CHARS];

static void load_char(FT_Face face, int char_code)
{
    if (FT_Load_Char(face, char_code, FT_LOAD_RENDER) != 0)
    {
        return;
    }
    int advance = round_up_26_6(face->glyph->advance.x);
    if (advance > max_advance)
    {
        max_advance = advance;
    }
    if ((face->glyph->bitmap.width == 0) ||
            (face->glyph->bitmap.rows == 0))
    {
        return;
    }
    char_infos[char_code].width = face->glyph->bitmap.width;
    char_infos[char_code].height = face->glyph->bitmap.rows;
    char_infos[char_code].top = face->glyph->bitmap_top;
    if (char_infos[char_code].top > max_top)
    {
        max_top = char_infos[char_code].top;
    }
    int bottom = char_infos[char_code].top - char_infos[char_code].height;
    if (bottom < min_bottom)
    {
        min_bottom = bottom;
    }
    char_infos[char_code].left = face->glyph->bitmap_left;
    char_infos[char_code].bitmap = malloc(char_infos[char_code].width * char_infos[char_code].height);
    memcpy(char_infos[char_code].bitmap,
            face->glyph->bitmap.buffer,
            char_infos[char_code].width * char_infos[char_code].height);
}

static const char * bare_header_name(const char * h_file_name)
{
    const char * p = rindex(h_file_name, '/');
    if (p == NULL)
    {
        p = h_file_name;
    }
    else
    {
        p++;
    }
    return p;
}

static char * include_guard_name(const char * h_file_name)
{
    const char * p = bare_header_name(h_file_name);
    char * guard_name = malloc(strlen(p) + 1);
    strcpy(guard_name, p);
    char * m = guard_name;
    while (*m != '\0')
    {
        if ('a' <= *m && *m <= 'z')
        {
            *m = toupper(*m);
        }
        else if (('0' <= *m && *m <= '9') || ('A' <= *m && *m <= 'Z'))
        {
            /* no change */
        }
        else
        {
            *m = '_';
        }
        m++;
    }
    return guard_name;
}

static void generate_bytes(FILE * file, const uint8_t * bytes, int count)
{
    for (int i = 0; i < count; i++)
    {
        if (i % 8 == 0)
        {
            fprintf(file, "    ");
        }
        fprintf(file, "0x%02xu,", bytes[i]);
        if ((i + 1) % 8 == 0)
        {
            fprintf(file, "\n");
        }
        else if (i < (count - 1))
        {
            fprintf(file, " ");
        }
    }
    if (count % 8 != 0)
    {
        fprintf(file, "\n");
    }
}

static void generate(const char * c_file_name)
{
    char * h_file_name = malloc(strlen(c_file_name) + 1);
    strcpy(h_file_name, c_file_name);
    h_file_name[strlen(h_file_name) - 1] = 'h';
    char * guard = include_guard_name(h_file_name);

    FILE * h_file = fopen(h_file_name, "wb");
    fprintf(h_file, "#ifndef %s\n", guard);
    fprintf(h_file, "#define %s\n\n", guard);
    fprintf(h_file, "#include <stdint.h>\n");
    fprintf(h_file, "typedef struct {\n    int width;\n    int height;\n    int top;\n    int left;\n    const uint8_t * bitmap;\n} fontgen_char_info_t;\n");
    fprintf(h_file, "typedef struct {\n    int line_height;\n    int advance;\n    int baseline_offset;\n    const fontgen_char_info_t ** char_infos;\n} fontgen_font_t;\n");
    fprintf(h_file, "extern const fontgen_font_t kfont;\n");
    fprintf(h_file, "#endif\n");
    fclose(h_file);

    FILE * c_file = fopen(c_file_name, "wb");
    fprintf(c_file, "#include \"%s\"\n", bare_header_name(h_file_name));
    fprintf(c_file, "#include <stddef.h>\n");
    for (int i = 0; i < N_CHARS; i++)
    {
        if (char_infos[i].width > 0)
        {
            fprintf(c_file, "static const uint8_t char_bitmap_%d[] = {\n", i);
            generate_bytes(c_file, char_infos[i].bitmap, char_infos[i].width * char_infos[i].height);
            fprintf(c_file, "};\n");
        }
        fprintf(c_file, "static const fontgen_char_info_t char_%d = {\n", i);
        fprintf(c_file, "    %d,\n", char_infos[i].width);
        fprintf(c_file, "    %d,\n", char_infos[i].height);
        fprintf(c_file, "    %d,\n", char_infos[i].top);
        fprintf(c_file, "    %d,\n", char_infos[i].left);
        if (char_infos[i].width > 0)
        {
            fprintf(c_file, "    char_bitmap_%d,\n", i);
        }
        else
        {
            fprintf(c_file, "    NULL,\n");
        }
        fprintf(c_file, "};\n\n");
    }
    fprintf(c_file, "const fontgen_char_info_t * char_infos[] = {\n");
    for (int i = 0; i < N_CHARS; i++)
    {
        fprintf(c_file, "    &char_%d,\n", i);
    }
    fprintf(c_file, "};\n");
    fprintf(c_file, "const fontgen_font_t kfont = {\n");
    fprintf(c_file, "    %d,\n", line_height);
    fprintf(c_file, "    %d,\n", max_advance);
    fprintf(c_file, "    %d,\n", baseline_offset);
    fprintf(c_file, "    char_infos,\n");
    fprintf(c_file, "};\n");
    fclose(c_file);
}

int main(int argc, char * argv[])
{
    /* Expect: font file, size, out file */
    if (argc != 4)
    {
        fprintf(stderr, "Incorrect arguments\n");
        return 1;
    }
    const char * font_file = argv[1];
    int size = atoi(argv[2]);
    const char * out_file = argv[3];

    FT_Library ft_library;
    if (FT_Init_FreeType(&ft_library) != 0)
    {
        fprintf(stderr, "Could not initialize freetype\n");
        return 2;
    }

    FT_Face face;
    if (FT_New_Face(ft_library, font_file, 0, &face) != 0)
    {
        fprintf(stderr, "Could not open %s\n", font_file);
        return 3;
    }

    FT_Set_Pixel_Sizes(face, 0, size);

    for (int i = 0; i < N_CHARS; i++)
    {
        load_char(face, i);
    }
    line_height = round_up_26_6(face->size->metrics.height);
    baseline_offset = (line_height - (max_top - min_bottom)) / 2 - min_bottom;

    generate(out_file);

    return 0;
}