atari2epson.c

/**
 *  atari2epson.c
 *  -------------
 *
 *  Convert Atari ST (GEM) 8x16 font files to Epson format.
 *
 *  The Atari font has a different structure as it is ordered by line
 *  rather than by character: The first 256 bytes represent the first
 *  line of the 256 ASCII characters. The second 256 bytes represend
 *  the second line of the characters etc.
 *
 *  The Epson format contains 16 bytes for the ASCII character 0, then
 *  16 bytes for the ASCII character 1 etc.
 *
 *  NOTE: Whole GDOS files are not supportet, only the raw raster data.
 *
 *  Usage: atari2epson fontfile [fontfile ...]
 *
 */

#include <libgen.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>


#define FONT_EXT  ".C16"


static void convert(FILE* fi, FILE* fo);
static void usage(const char* progname);


int main(int argc, char* argv[])
{
    if (argc < 2) {
        usage(argv[0]);
        exit(1);
    }

    for (int i = 1; i < argc; ++i) {
        char* infile  = argv[i];
        char* outfile = malloc(strlen(infile) + 4);
        char* ext     = strrchr(basename(infile), '.');
        FILE* fi;

        if (ext != NULL) {
            strcpy(outfile, infile);
            strcpy(strrchr(outfile, '.'), FONT_EXT);
        } else {
            strcat(strcpy(outfile, infile), FONT_EXT);
        }

        printf("%s", infile);

        fi = fopen(infile, "rb");

        if (fi == NULL) {
            puts(" cannot be opened.");
        } else {
            FILE* fo = fopen(outfile, "wb");

            if (fo == NULL) {
                puts(": Cannot open output file.");
            } else {
                fseek(fi, 0, SEEK_END);

                if (ftell(fi) != 0x1000) {
                    puts(" is not 4096 bytes long.");
                } else {
                    printf(" -> %s\n", outfile);
                    fseek(fi, 0, SEEK_SET);
                    convert(fi, fo);
                }

                fclose(fo);
            }

            fclose(fi);
        }
    }

    return 0;
}


void
convert(FILE* fi, FILE* fo)
{
    char inbuf[0x1000];
    char outbuf[0x1000];

    fread(inbuf, 0x1000, 1, fi);

    for (int c = 0; c < 256; ++c) {
        for (int l = 0; l < 16; ++l) {
            outbuf[c * 16 + l] = inbuf[c + 256 * l];
        }
    }

    fwrite(outbuf, 0x1000, 1, fo);
}


void
usage(const char* progname)
{
    printf("Usage: %s fontfile [fontfile ...]\n", progname);
}