Task 740: .TTF File Format
Task 740: .TTF File Format
The task involves developing code related to the .TTF (TrueType Font) file format. Below, I address each numbered requirement based on the specifications obtained from reliable sources, such as the Apple TrueType Reference Manual. The .TTF format is a binary file format for scalable fonts, consisting of an offset subtable followed by a table directory and concatenated font tables. All data is big-endian, and tables are 4-byte aligned.
1. List of All Properties Intrinsic to the .TTF File Format
The intrinsic properties refer to the core structural elements in the file header (offset subtable) and table directory, which define the file's organization and are essential for parsing any .TTF file. These are derived directly from the format specification and do not include the contents of individual font tables (e.g., 'head' or 'cmap'), as those vary by font and are not universal to the file system structure.
- Scaler Type (uint32): A identifier for the font type, typically 0x00010000 for TrueType outlines or 'true' (0x74727565) on some platforms.
- Number of Tables (uint16): The count of font tables in the file.
- Search Range (uint16): Computed as (maximum power of 2 less than or equal to numTables) × 16, used for binary search optimization in the table directory.
- Entry Selector (uint16): Computed as log₂(searchRange / 16), indicating the number of binary search iterations needed.
- Range Shift (uint16): Computed as (numTables × 16) - searchRange, used as an offset in binary search.
- Table Directory Entries (repeated for each table; each entry is 16 bytes):
- Tag (uint32): A 4-character ASCII identifier for the table (e.g., 'head' as 0x68656164).
- Checksum (uint32): The unsigned sum of all 32-bit values in the table, for integrity verification.
- Offset (uint32): The byte offset from the file start to the beginning of the table.
- Length (uint32): The length of the table in bytes (unpadded).
These properties are fundamental to the file format's structure and must be present in every valid .TTF file.
2. Two Direct Download Links for .TTF Files
The following are direct download links to freely available .TTF files from open repositories. These are single .TTF files (not archives) and are licensed for public use (e.g., under Apache or SIL Open Font License).
- https://raw.githubusercontent.com/openmaptiles/fonts/master/roboto/Roboto-Regular.ttf (Roboto Regular font)
- https://raw.githubusercontent.com/taylor/fonts/master/LiberationSans-Regular.ttf (Liberation Sans Regular font)
3. Ghost Blog Embedded HTML JavaScript for Drag-and-Drop .TTF Property Dump
The following is a self-contained HTML snippet with embedded JavaScript that can be embedded in a Ghost blog post (or any HTML context). It creates a drag-and-drop area where a user can drop a .TTF file. The script reads the file as an ArrayBuffer, parses the properties listed in item 1 using DataView, and displays them on the screen in a structured format. Error handling is included for invalid files.
Drag and drop a .TTF file here
4. Python Class for .TTF Handling
The following Python class uses the struct module to decode, read, and write .TTF files. It opens a file, parses the properties, prints them to the console, and supports writing modifications (e.g., updating a checksum) back to a new file.
import struct
import os
class TTFHandler:
def __init__(self, filepath):
self.filepath = filepath
self.scaler_type = None
self.num_tables = None
self.search_range = None
self.entry_selector = None
self.range_shift = None
self.tables = [] # List of dicts: {'tag': str, 'checksum': int, 'offset': int, 'length': int}
self.data = None # Full file bytes
def read(self):
with open(self.filepath, 'rb') as f:
self.data = f.read()
if len(self.data) < 12:
raise ValueError("Invalid .TTF file: too short")
self.scaler_type, self.num_tables, self.search_range, self.entry_selector, self.range_shift = struct.unpack('>IHHHH', self.data[:12])
offset = 12
for _ in range(self.num_tables):
if offset + 16 > len(self.data):
raise ValueError("Invalid .TTF file: incomplete table directory")
tag_bytes, checksum, table_offset, length = struct.unpack('>4sIII', self.data[offset:offset+16])
tag = tag_bytes.decode('ascii').rstrip()
self.tables.append({'tag': tag, 'checksum': checksum, 'offset': table_offset, 'length': length})
offset += 16
def print_properties(self):
if self.scaler_type is None:
raise ValueError("File not read yet")
print(f"Scaler Type: 0x{self.scaler_type:08X}")
print(f"Number of Tables: {self.num_tables}")
print(f"Search Range: {self.search_range}")
print(f"Entry Selector: {self.entry_selector}")
print(f"Range Shift: {self.range_shift}")
print("\nTable Directory:")
for i, table in enumerate(self.tables, 1):
print(f"Table {i}:")
print(f" Tag: {table['tag']}")
print(f" Checksum: 0x{table['checksum']:08X}")
print(f" Offset: {table['offset']}")
print(f" Length: {table['length']}")
def write(self, output_filepath):
if self.data is None:
raise ValueError("File not read yet")
# Example modification: update first table checksum if exists (for demonstration)
if self.tables:
self.tables[0]['checksum'] += 1 # Arbitrary change
offset = 12
new_data = bytearray(self.data)
for table in self.tables:
struct.pack_into('>4sIII', new_data, offset, table['tag'].encode('ascii').ljust(4, b' '), table['checksum'], table['offset'], table['length'])
offset += 16
with open(output_filepath, 'wb') as f:
f.write(new_data)
# Example usage:
# handler = TTFHandler('example.ttf')
# handler.read()
# handler.print_properties()
# handler.write('modified.ttf')
5. Java Class for .TTF Handling
The following Java class uses DataInputStream for decoding and reading, and DataOutputStream for writing. It parses the properties, prints them to the console, and supports writing modifications.
import java.io.*;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
public class TTFHandler {
private String filepath;
private int scalerType;
private short numTables;
private short searchRange;
private short entrySelector;
private short rangeShift;
private TableEntry[] tables;
private byte[] data;
static class TableEntry {
String tag;
int checksum;
int offset;
int length;
}
public TTFHandler(String filepath) {
this.filepath = filepath;
}
public void read() throws IOException {
try (FileInputStream fis = new FileInputStream(filepath);
DataInputStream dis = new DataInputStream(fis)) {
data = new byte[(int) new File(filepath).length()];
dis.readFully(data);
}
ByteBuffer bb = ByteBuffer.wrap(data).order(ByteOrder.BIG_ENDIAN);
scalerType = bb.getInt(0);
numTables = bb.getShort(4);
searchRange = bb.getShort(6);
entrySelector = bb.getShort(8);
rangeShift = bb.getShort(10);
tables = new TableEntry[numTables];
int pos = 12;
for (int i = 0; i < numTables; i++) {
tables[i] = new TableEntry();
byte[] tagBytes = new byte[4];
bb.position(pos);
bb.get(tagBytes);
tables[i].tag = new String(tagBytes).trim();
tables[i].checksum = bb.getInt(pos + 4);
tables[i].offset = bb.getInt(pos + 8);
tables[i].length = bb.getInt(pos + 12);
pos += 16;
}
}
public void printProperties() {
System.out.printf("Scaler Type: 0x%08X%n", scalerType);
System.out.printf("Number of Tables: %d%n", numTables);
System.out.printf("Search Range: %d%n", searchRange);
System.out.printf("Entry Selector: %d%n", entrySelector);
System.out.printf("Range Shift: %d%n", rangeShift);
System.out.println("\nTable Directory:");
for (int i = 0; i < tables.length; i++) {
System.out.printf("Table %d:%n", i + 1);
System.out.printf(" Tag: %s%n", tables[i].tag);
System.out.printf(" Checksum: 0x%08X%n", tables[i].checksum);
System.out.printf(" Offset: %d%n", tables[i].offset);
System.out.printf(" Length: %d%n", tables[i].length);
}
}
public void write(String outputFilepath) throws IOException {
if (data == null) throw new IllegalStateException("File not read yet");
// Example modification: increment first table checksum
if (tables.length > 0) {
tables[0].checksum += 1;
ByteBuffer bb = ByteBuffer.wrap(data).order(ByteOrder.BIG_ENDIAN);
int pos = 12;
for (TableEntry table : tables) {
bb.position(pos);
byte[] tagBytes = table.tag.getBytes("US-ASCII");
for (byte b : tagBytes) bb.put(b);
for (int j = tagBytes.length; j < 4; j++) bb.put((byte) ' ');
bb.putInt(table.checksum);
bb.putInt(table.offset);
bb.putInt(table.length);
pos += 16;
}
}
try (FileOutputStream fos = new FileOutputStream(outputFilepath)) {
fos.write(data);
}
}
// Example usage:
// public static void main(String[] args) throws IOException {
// TTFHandler handler = new TTFHandler("example.ttf");
// handler.read();
// handler.printProperties();
// handler.write("modified.ttf");
// }
}
6. JavaScript Class for .TTF Handling
The following JavaScript class uses DataView for parsing in a browser or Node.js environment (with file reading via fs in Node). It decodes, reads, prints to console, and supports writing (in Node.js).
const fs = require('fs'); // For Node.js file I/O; omit in browser
class TTFHandler {
constructor(filepath) {
this.filepath = filepath;
this.scalerType = null;
this.numTables = null;
this.searchRange = null;
this.entrySelector = null;
this.rangeShift = null;
this.tables = [];
this.buffer = null;
}
read() {
this.buffer = fs.readFileSync(this.filepath); // Node.js; in browser, use FileReader
const view = new DataView(this.buffer.buffer);
this.scalerType = view.getUint32(0);
this.numTables = view.getUint16(4);
this.searchRange = view.getUint16(6);
this.entrySelector = view.getUint16(8);
this.rangeShift = view.getUint16(10);
let offset = 12;
for (let i = 0; i < this.numTables; i++) {
const tag = String.fromCharCode(view.getUint8(offset), view.getUint8(offset + 1), view.getUint8(offset + 2), view.getUint8(offset + 3)).trim();
const checksum = view.getUint32(offset + 4);
const tableOffset = view.getUint32(offset + 8);
const length = view.getUint32(offset + 12);
this.tables.push({ tag, checksum, offset: tableOffset, length });
offset += 16;
}
}
printProperties() {
console.log(`Scaler Type: 0x${this.scalerType.toString(16).padStart(8, '0')}`);
console.log(`Number of Tables: ${this.numTables}`);
console.log(`Search Range: ${this.searchRange}`);
console.log(`Entry Selector: ${this.entrySelector}`);
console.log(`Range Shift: ${this.rangeShift}`);
console.log('\nTable Directory:');
this.tables.forEach((table, i) => {
console.log(`Table ${i + 1}:`);
console.log(` Tag: ${table.tag}`);
console.log(` Checksum: 0x${table.checksum.toString(16).padStart(8, '0')}`);
console.log(` Offset: ${table.offset}`);
console.log(` Length: ${table.length}`);
});
}
write(outputFilepath) {
if (!this.buffer) throw new Error('File not read yet');
const view = new DataView(this.buffer.buffer);
// Example modification: increment first table checksum
if (this.tables.length > 0) {
this.tables[0].checksum += 1;
let offset = 12;
this.tables.forEach((table) => {
for (let j = 0; j < 4; j++) {
view.setUint8(offset + j, table.tag.charCodeAt(j) || 32); // Pad with space
}
view.setUint32(offset + 4, table.checksum);
view.setUint32(offset + 8, table.offset);
view.setUint32(offset + 12, table.length);
offset += 16;
});
}
fs.writeFileSync(outputFilepath, this.buffer);
}
}
// Example usage in Node.js:
// const handler = new TTFHandler('example.ttf');
// handler.read();
// handler.printProperties();
// handler.write('modified.ttf');
7. C++ Class for .TTF Handling
The following C++ class uses fstream for file I/O and manual byte reading/writing. It decodes, reads, prints to console, and supports writing modifications. (Note: C does not have native classes; C++ is used for object-oriented structure.)
#include <iostream>
#include <fstream>
#include <vector>
#include <string>
#include <iomanip>
#include <cstring>
struct TableEntry {
std::string tag;
uint32_t checksum;
uint32_t offset;
uint32_t length;
};
class TTFHandler {
private:
std::string filepath;
uint32_t scaler_type;
uint16_t num_tables;
uint16_t search_range;
uint16_t entry_selector;
uint16_t range_shift;
std::vector<TableEntry> tables;
std::vector<char> data;
public:
TTFHandler(const std::string& fp) : filepath(fp), scaler_type(0), num_tables(0), search_range(0), entry_selector(0), range_shift(0) {}
void read() {
std::ifstream file(filepath, std::ios::binary | std::ios::ate);
if (!file) throw std::runtime_error("Cannot open file");
size_t size = file.tellg();
data.resize(size);
file.seekg(0);
file.read(data.data(), size);
if (size < 12) throw std::runtime_error("Invalid .TTF file: too short");
memcpy(&scaler_type, data.data(), 4);
memcpy(&num_tables, data.data() + 4, 2);
memcpy(&search_range, data.data() + 6, 2);
memcpy(&entry_selector, data.data() + 8, 2);
memcpy(&range_shift, data.data() + 10, 2);
// Swap if little-endian host (assuming big-endian file)
scaler_type = __builtin_bswap32(scaler_type);
num_tables = __builtin_bswap16(num_tables);
search_range = __builtin_bswap16(search_range);
entry_selector = __builtin_bswap16(entry_selector);
range_shift = __builtin_bswap16(range_shift);
size_t pos = 12;
tables.resize(num_tables);
for (uint16_t i = 0; i < num_tables; ++i) {
if (pos + 16 > size) throw std::runtime_error("Invalid .TTF file: incomplete directory");
char tag_buf[5] = {0};
memcpy(tag_buf, data.data() + pos, 4);
tables[i].tag = std::string(tag_buf).substr(0, strnlen(tag_buf, 4));
memcpy(&tables[i].checksum, data.data() + pos + 4, 4);
memcpy(&tables[i].offset, data.data() + pos + 8, 4);
memcpy(&tables[i].length, data.data() + pos + 12, 4);
tables[i].checksum = __builtin_bswap32(tables[i].checksum);
tables[i].offset = __builtin_bswap32(tables[i].offset);
tables[i].length = __builtin_bswap32(tables[i].length);
pos += 16;
}
}
void printProperties() const {
std::cout << "Scaler Type: 0x" << std::hex << std::setw(8) << std::setfill('0') << scaler_type << std::dec << std::endl;
std::cout << "Number of Tables: " << num_tables << std::endl;
std::cout << "Search Range: " << search_range << std::endl;
std::cout << "Entry Selector: " << entry_selector << std::endl;
std::cout << "Range Shift: " << range_shift << std::endl;
std::cout << "\nTable Directory:" << std::endl;
for (size_t i = 0; i < tables.size(); ++i) {
std::cout << "Table " << (i + 1) << ":" << std::endl;
std::cout << " Tag: " << tables[i].tag << std::endl;
std::cout << " Checksum: 0x" << std::hex << std::setw(8) << std::setfill('0') << tables[i].checksum << std::dec << std::endl;
std::cout << " Offset: " << tables[i].offset << std::endl;
std::cout << " Length: " << tables[i].length << std::endl;
}
}
void write(const std::string& output_filepath) {
if (data.empty()) throw std::runtime_error("File not read yet");
// Example modification: increment first table checksum
if (!tables.empty()) {
tables[0].checksum += 1;
size_t pos = 12;
for (const auto& table : tables) {
uint32_t be_checksum = __builtin_bswap32(table.checksum);
uint32_t be_offset = __builtin_bswap32(table.offset);
uint32_t be_length = __builtin_bswap32(table.length);
char tag_buf[4];
strncpy(tag_buf, table.tag.c_str(), 4);
for (size_t j = table.tag.size(); j < 4; ++j) tag_buf[j] = ' ';
memcpy(data.data() + pos, tag_buf, 4);
memcpy(data.data() + pos + 4, &be_checksum, 4);
memcpy(data.data() + pos + 8, &be_offset, 4);
memcpy(data.data() + pos + 12, &be_length, 4);
pos += 16;
}
}
std::ofstream out(output_filepath, std::ios::binary);
if (!out) throw std::runtime_error("Cannot write file");
out.write(data.data(), data.size());
}
};
// Example usage:
// int main() {
// try {
// TTFHandler handler("example.ttf");
// handler.read();
// handler.printProperties();
// handler.write("modified.ttf");
// } catch (const std::exception& e) {
// std::cerr << e.what() << std::endl;
// }
// return 0;
// }