How to Compare Font Differences Using 'ftxdiff' (with examples)

The ftxdiff command is a tool provided by Apple that allows developers and designers to compare differences between two font files. This can be incredibly useful when working with multiple versions of a font or when needing to ensure consistency across different platforms and projects. The command provides detailed comparisons and offers several options to tailor the output according to specific needs.

Use case 1: Output differences to a specific text file

Code:

ftxdiff --output path/to/fontdiff_file.txt path/to/font_file1.ttc path/to/font_file2.ttc

Motivation:

When working with font files, especially in a collaborative environment or as part of documentation, it’s often necessary to record the differences between fonts in a persistent way. By directing the output to a specific text file, you can easily share the results with colleagues or keep a record for future reference. This is particularly useful for designers or developers who need to track changes made across versions of a typeface.

Explanation:

• --output path/to/fontdiff_file.txt: This argument specifies the path where the differences between the two fonts should be saved. It allows users to keep the output organized and easily accessible.

• path/to/font_file1.ttc: This specifies the path to the first font file in TrueType Collection format that you want to compare.

• path/to/font_file2.ttc: This specifies the path to the second font file for the comparison.

Example Output:

The output in the text file could include details such as different glyph metrics, character mappings, or any substituted characters between the two fonts, helping to identify exactly how the fonts differ.

Use case 2: Include glyph names in output

Code:

ftxdiff --include-glyph-names path/to/font_file1.ttc path/to/font_file2.ttc

Motivation:

Including glyph names in your comparison output can be crucial for understanding exactly which characters differ. Glyph names provide a human-readable identifier for each glyph in the font, such as “A”, “B”, “G_breve”, etc., making it easier to pinpoint specific changes in glyph design or encoding. This is especially important for typographers or anyone specifically working on the design aspects of a font, as glyph names relate directly to the visual elements of the font.

Explanation:

• --include-glyph-names: This option tells ftxdiff to include the names of the glyphs in the output, providing more context about each difference.

• path/to/font_file1.ttc: Path to the first font file to be analyzed.

• path/to/font_file2.ttc: Path to the second font file to compare against.

Example Output:

The output might list differences such as glyph “A” has a different metadata or outline in font file 1 compared to font file 2, providing insight into what specific glyphs have been altered or are not consistent between two versions.

Use case 3: Include unicode names in output

Code:

ftxdiff --include-unicode-names path/to/font_file1.ttc path/to/font_file2.ttc

Motivation:

Unicode names are a key aspect of understanding font file differences, especially if you’re working with fonts that include many characters from various scripts or with special symbols. By including Unicode names in the output, you can get a clear picture of which specific characters differ between the fonts using their Unicode point. This is crucial for developers and linguists who are concerned with the coding and representation of characters across different software and documents.

Explanation:

• --include-unicode-names: This option instructs ftxdiff to output the Unicode names of the characters that have differences in their representation between the two font files.

• path/to/font_file1.ttc: Path to the first font file selected for comparison.

• path/to/font_file2.ttc: Path to the second font file for comparison purposes.

Example Output:

The comparison output might reveal that the character at U+0041 (“LATIN CAPITAL LETTER A”) has different characteristics between the two font files, such as variations in the glyph design or kerning values, providing essential information for ensuring text renders correctly.

Conclusion:

The ftxdiff tool is a powerful utility for anyone working with fonts, allowing you to efficiently compare two font files and output the differences in a structured and informative manner. Whether you need to record changes, focus on specific glyph adjustments, or analyze Unicode character differences, the various options offered by ftxdiff provide the flexibility needed to handle complex font comparison tasks.