This is Cram, a texture packing system in C.

About Cram

Cram is a portable C texture packing system intended for use in games, particularly 2D sprite games. Texture switching is an expensive operation, especially on low-end GPUs, so for performance it is imperative to pack sprites into textures to enable sprite batching.

Cram uses the maximal rectangles algorithm with the best area fit heuristic to pack your images. It automatically de-duplicates images to save space.

Cram ships with a default command line interface implemented in C, but if you wish you can configure CMake to build a shared library which will allow you to bind its essential functions to another language.

Usage

Usage: cram input_dir output_dir atlas_name [--padding padding_value] [--notrim] [--dimension max_dimension]

Cram expects input in PNG and outputs a PNG and a JSON metadata file that you can use to properly display the images in your game. Cram will recursively walk all the subdirectories of input_dir to generate your texture atlas.

Padding is set to 0 by default. If you need to use linear filtering, set padding to at least 1. If you need to use texture compression, set padding to at least 4.

Trimming is on by default. Use --notrim if for some weird reason you want it off.

Max dimension value is set to 8192 by default since that is a common max texture size for basically every GPU out there. Use --dimension [max_dimension] to override this maximum.

Dependencies

Cram depends on the C runtime.

libCram uses stb_ds for image hashing, and stb_image for image loading.

The CLI uses stb_image_write to output PNG images, and a portable dirent.h for a Windows-compatible dirent implemention.

Building Cram

For *nix platforms, use CMake:

$ mkdir build/
$ cd build
$ cmake ../
$ make

For Windows, use CMake to generate a visualc project.

License

Cram is licensed under the zlib license. See LICENSE for details.