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Texture packer and resource bundler. Use the rucksack executable to build your resources file, and then depend on librucksack in-game to get the resources out at runtime. Alternately, roll your own resource-loading code using the file format detailed at the end of this README.

rucksack defines a resource manifest file format which is loosely based on JSON but accepts comments, extra punctuation, and unquoted strings. This manifest file tells rucksack which files to bundle and how to store them. rucksack uses a rectangle bin packing algorithm to efficiently store multiple images into a single texture, otherwise known as a "sprite sheet".

Command Line Usage

rucksack v3.1.0

Usage: rucksack [command] [command-options]

  help       get info on how to use a command
  bundle     parses an assets json file and keeps a bundle up to date
  cat        extracts a single file from the bundle and writes it to stdout
  ls         lists all resources in a bundle
  rm         remove a file from the bundle
  strip      make an existing bundle as small as possible
  unpack     create a directory with the bundle contents

Library Usage

#include <rucksack/rucksack.h>

int main() {
    struct RuckSackBundle *bundle;
    rucksack_bundle_open(bundle_name, &bundle);

    struct RuckSackFileEntry *entry = rucksack_bundle_find_file(bundle, "blah");
    size_t size = rucksack_file_size(entry);
    unsigned char *buffer = malloc(size);
    rucksack_bundle_file_read(bundle, entry, buf);
    // buffer now contains the contents of the file indexed by "blah"



Pre-Built Packages

  • Ubuntu PPA

    sudo apt-add-repository ppa:andrewrk/rucksack
    sudo apt-get update
    sudo apt-get install rucksack

From Source

  1. mkdir build && cd build && cmake ..
  2. Verify that all dependencies say "OK".
  3. make && sudo make install

JSON Reference


// comments are OK :)
// single quotes, double quotes, and no quotes are OK
  // one-off files you want to directly save into the bundle
  files: {
    file1Name: {
      path: "path/to/file",
  // if you want to avoid manually specifying every file, you can glob
  globFiles: [
      path: "path/to/dir",
      glob: "*",
      prefix: "abc_", // prepended to the key
  // spritesheet generation
  textures: {
    texture1Name: {
      // 1024x1024 is the default.
      maxWidth: 1024,
      maxHeight: 1024,

      // By default rucksack enforces that the width and height of a texture
      // will be a power of 2. Set pow2 to false to disable this.
      pow2: true,

      // rucksack efficiently packs textures by sometimes rotating images
      // to make them fit better, and you can compensate for this by using
      // different UV coords when the images are rotated. If you for some
      // reason want to disable this feature, you can set allowRotate90 to
      // false.
      allowRotate90: true,

      globImages: [
          path: "path/to/dir",
          glob: "*",
          prefix: "abc_", // prepended to the key

          // can be any of these strings:
          // "top", "left", "bottom", "right"
          // "topleft", "topright", "bottomleft", "bottomright"
          // "center"
          // or it can be an object like this: {x: 13, y: 19}
          anchor: "center",
      images: {
        image1Name: {
          // can be any image format supported by FreeImage
          path: "path/to/image.png",

          // can be any of these strings:
          // "top", "left", "bottom", "right"
          // "topleft", "topright", "bottomleft", "bottomright"
          // "center"
          // or it can be an object like this: {x: 13, y: 19}
          anchor: "center",

RuckSack Bundle File Format

The main header identifies the file and tells you some metadata about the rest of the header entries.

The basic data supported by rucksack is a file. In this case the offset that a header entry points to is the raw file data. Some files in a rucksack bundle are textures, also known as spritesheets. This is described by Texture Format below.

Offset | Contents
     0 | 16 byte UUID - 60 70 c8 99 82 a1 41 84 89 51 08 c9 1c c9 b6 20
    16 | uint32be file format version. bumped when incompatible changes made.
    20 | uint32be offset of first header entry from file start
    24 | uint32be number of header entries

Header Entry Format

Offset | Contents
     0 | uint32be size of this header entry in bytes
     4 | uint64be offset of this entry's file contents
    12 | uint64be actual size of the file contents in bytes
    20 | uint64be number of allocated bytes for this file
    28 | uint32be file mtime
    32 | uint32be key size in bytes
    36 | key bytes

Texture Format

Offset | Contents
     0 | 16 byte UUID 0e b1 4c 84 47 4c b3 ad a6 bd 93 e4 be a5 46 ba
    16 | uint32be offset of the actual image data from 0 in this struct
    20 | uint32be number of images in this texture
    24 | uint32be offset of the first image entry from 0 in this struct
    28 | uint32be max_width used when creating this texture
    32 | uint32be max_height used when creating this texture
    36 | uint8 pow2 value used when creating this texture
    37 | uint8 allow_r90 value used when creating this texture

Image Entry Format

Offset | Contents
     0 | uint32be size of this image entry header in bytes
     4 | uint32be anchor position enum value
     8 | uint32be anchor x multiplied by 16384
    12 | uint32be anchor y multiplied by 16384
    16 | uint32be image x
    20 | uint32be image y
    24 | uint32be unrotated image width
    28 | uint32be unrotated image height
    32 | uint8 boolean whether the image is rotated clockwise 90 degrees
    33 | uint32be key size in bytes
    37 | key bytes

Projects Using rucksack

Feel free to make a pull request adding to this list.

  • Genesis - Digital Audio Workstation
  • spacefight - 3D asteroids prototype
  • grapple - prototyping a 4 player arcade game based on a grapple gun and a physics engine


texture packer and resource bundler




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