afm/parse.js

Adobe Font Metrics

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
var fs_1 = require("fs");
/**
parseCharMetrics() takes a single line from the "CharMetrics" section in an
AFM file, and extracts the crucial metrics for that character. For example, the
line describing capital A in Times-Roman from Adobe's Core14 font set is this:

    C 65 ; WX 722 ; N A ; B 15 0 706 674 ;

For which parseCharMetrics() would return a plain object:

    { charCode: 65, width: 722, name: 'A' }

From https://partners.adobe.com/public/developer/en/font/5004.AFM_Spec.pdf:

> `C integer`: Decimal value of default character code (−1 if not encoded).
> `CH` hex`:   Same as C, but the character code is given in hexadecimal.
               Either C or CH is required
> `WX number`: Width of character.
> `N name`:    (Optional.) PostScript language character name.
*/
function parseCharMetrics(line) {
    var charCode_match = line.match(/C\s+(\d+|-1)/);
    var width_match = line.match(/WX\s+(\d+)/);
    var name_match = line.match(/N\s+(\w+)/);
    var charCode = charCode_match ? parseInt(charCode_match[1], 10) : null;
    var width = width_match ? parseInt(width_match[1], 10) : null;
    var name = name_match ? name_match[1] : null;
    return { charCode: charCode, width: width, name: name };
}
exports.parseCharMetrics = parseCharMetrics;
/**
parseFontMetrics() takes an entire AFM file as a string, finds the
"CharMetrics" section, and parses all of the char metrics lines from that
section, returning an Array of those charmetrics.
*/
function parseFontMetrics(data) {
    var start_match = data.match(/^StartCharMetrics\s+(\d+)/m);
    var end_match = data.match(/^EndCharMetrics/m);
    var char_metrics_start = start_match.index + start_match[0].length;
    var char_metrics_data = data.slice(char_metrics_start, end_match.index);
    var char_metrics_lines = char_metrics_data.trim().split(/\r\n|\r|\n|\t/);
    return char_metrics_lines.map(parseCharMetrics);
}
exports.parseFontMetrics = parseFontMetrics;
/**
Parse Adobe Font Metrics data from inputStream
and write array of CharMetrics objects to outputStream as JSON.
*/
function convert(inputStream, outputStream, callback) {
    var chunks = [];
    inputStream
        .on('data', function (chunk) { chunks.push(chunk); })
        .on('end', function () {
        var data = Buffer.concat(chunks).toString('ascii');
        var charMetrics = parseFontMetrics(data);
        var json = JSON.stringify(charMetrics);
        outputStream.write(json);
    });
}
exports.convert = convert;
if (require.main === module) {
    var _a = process.argv, input_argument = _a[2], output_argument = _a[3];
    var inputStream = input_argument ? fs_1.createReadStream(input_argument) : process.stdin;
    var outputStream = output_argument ? fs_1.createWriteStream(output_argument) : process.stdout;
    convert(inputStream, outputStream, function (error) {
        if (error)
            throw error;
        process.exit();
    });
}