CBZFit

Fit manga and comic archives to your screen.

CBZFit resizes images in CBZ archives for a target display resolution while preserving their aspect ratio and original image format. Images that already fit are copied without re-encoding. CBZFit preserves non-image members, and leaves the source archive unchanged by default.

Features

• Resize portrait pages and landscape spreads for a target display
• Preserve JPEG, PNG, and WebP image formats
• Copy images without re-encoding when resizing is unnecessary
• Preserve archive member order and non-image members such as ComicInfo.xml
• Derive a safe destination name when DESTINATION is omitted
• Verify generated archives before publication
• Publish output atomically to avoid incomplete destination archives
• Display interactive transformation and verification progress
• Report image counts, elapsed time, and archive-size change

Requirements

• Python 3.12 or later

Installation

Recommended: pipx

Install CBZFit from PyPI with pipx:

pipx install cbzfit

Upgrade an existing installation with:

pipx upgrade cbzfit

Usage

cbzfit SOURCE [DESTINATION] --screen-width PIXELS --screen-height PIXELS

Screen dimensions must be positive and supplied in portrait orientation, with the width no greater than the height.

For example, resize an archive to a 1404 x 1872 display:

cbzfit "Manga Volume 01.cbz" --screen-width 1404 --screen-height 1872

When DESTINATION is omitted, the final extension of SOURCE must be .cbz or .zip. CBZFit inserts [CBZFit] before that extension and writes the output beside the source. The above example creates:

Manga Volume 01 [CBZFit].cbz

Specify the destination

For a source with another extension or no extension, provide DESTINATION explicitly.

cbzfit zipped-images.data comic-resized.cbz --screen-width 1404 --screen-height 1872

Landscape pages

By default, landscape images are fitted to the display in landscape orientation. To use portrait display bounds for every image:

cbzfit manga.cbz --screen-width 1404 --screen-height 1872 --no-landscape-display

Upscaling

Images smaller than the target display are not enlarged by default. Enable upscaling with:

cbzfit comic.cbz --screen-width 1404 --screen-height 1872 --upscale

Existing destinations

The default conflict mode is error, which stops without modifying the source or destination. Use --conflict replace to replace an existing destination or process an archive in place:

cbzfit manga.cbz manga.cbz --screen-width 1404 --screen-height 1872 --conflict replace

Output verification

Select verification with --verify MODE:

• structure, the default, reopens the generated archive and validates its ZIP structure
• crc reads every output member and validates its compressed data and CRC
• none trusts successful ZIP finalization and skips reopening the output

For the strongest verification:

cbzfit comic.cbz --screen-width 1404 --screen-height 1872 --verify crc

Progress

Progress is shown automatically when standard error is an interactive terminal. Transformation and CRC verification display member-based progress bars. Progress is written to standard error so the final summary remains on standard output.

Progress is suppressed when standard error is redirected. Disable it explicitly with:

cbzfit manga.cbz --screen-width 1404 --screen-height 1872 --no-progress

Completion summary

Successful processing prints a three-line summary:

Output: optimized.cbz completed in 10.5 s
└─Images: 200 total, 100 transformed, 100 unchanged. Other members copied: 100
└─Size: 180.0 MiB -> 95.8 MiB, 46.8 % decrease

Run the built-in help for the complete command reference:

cbzfit --help

Supported files and behavior

CBZFit processes ZIP-based archives containing static JPEG, PNG, or WebP images.

• Resized images preserve their source image format.
• Images that already fit are copied without re-encoding.
• Non-image members, including ComicInfo.xml, are preserved in archive order but are not interpreted or edited.
• The source archive remains unchanged unless in-place replacement is explicitly requested.
• Generated output is finalized, optionally verified, and published atomically.

CBZFit rejects:

• archives without supported images
• invalid ZIP archives
• animated images
• encrypted archive members
• symbolic links and other special ZIP member types
• unsafe or duplicate member paths
• unsupported ZIP compression methods
• image content that does not match its filename extension
• archive members or archives that exceed the configured safety limits
• compressed members whose declared expansion exceeds 100:1 beyond the 100 KiB allowance

Development

Clone the repository and create a virtual environment:

git clone https://github.com/luigibrosse/cbzfit.git
cd cbzfit
python -m venv .venv

Activate it:

# Windows PowerShell
.venv\Scripts\Activate.ps1

# Linux or macOS
source .venv/bin/activate

Install CBZFit in editable mode with the development dependencies:

python -m pip install -e ".[dev]"

Run Ruff and the complete test suite with branch coverage:

python -m ruff check .
python -m pytest --cov=cbzfit --cov-branch --cov-report=term-missing --cov-fail-under=100

Build and validate the distributions:

python -m pip install --upgrade build twine
python -m build
python -m twine check --strict dist/*

Versioning

CBZFit follows Semantic Versioning. Version 0.1.0 is an initial pre-1.0 release. Before 1.0, minor releases may introduce documented CLI or behavior changes. Patch releases are intended for backward-compatible fixes and documentation or packaging corrections.

User-visible changes are recorded in CHANGELOG.md. src/cbzfit/__init__.py is the authoritative version source through cbzfit.__version__; Hatchling derives the package metadata version from it.

License

CBZFit is licensed under the GNU General Public License v3.0 or later.