Spritemapper

Spritemapper is an application that merges multiple images into one and generates CSS positioning for the corresponding slices.

The package consists of a simple command-line tool that "does the job" and a Python library including its own PNG and CSS parser. The choice of writing/bundling this was to stay off 3rd-party requirements. Anybody who has ever had the pleasant job of installing PIL on various platforms should have a pretty good idea about what we're trying to avoid.

There are multiple alternatives to Spritemapper, but they all require a bit too much manual labour, whereas Spritemapper reads your current CSS, replacing background images and position with the generated result.

This technique drastically improves your website's loading speed, effectively reducing bandwidth by downloading fewer images.

Spritemapper in action

Here's a simple example illustrating what Spritemapper will do with your CSS:

.emote.smile {
  background: red url(../img/emoticons/smile.png) no-repeat;
}
.emote.grin {
  background: white url(../img/emoticons/grin.png) no-repeat;
}

turns into:

.emote.smile {
  background: red url(../img/emoticons.png) no-repeat 0 0;
}
.emote.grin {
  background: white url(../img/emoticons.png) no-repeat 0 -16px;
}

Check our homepage for real life examples.

Usage

-h, --help

show a help message and exit

-c INI, --conf=INI

read base configuration from INI (see Configuration options)

--padding=N

keep N pixels of padding between sprites

Configuration options

Configuration options can be specified in one of two ways: inline in the CSS, or using passing an INI file with defaults. For CSS it looks something like:

/* spritemapper.output_css = foofile.css

You can do the exact equivalent using an INI file, like this:

[spritemapper]
output_css = foofile.css

It's important to note that all paths are relative to the CSS file being processed.

base_url

a url at which the resulting css and image files can be reached. by default uses file-relative paths (recommended).

sprite_dirs

a list of directories within which to allow spritemaps to be generated. by default all directories are eligible.

recursive

set if sub-spritemaps should be generated when sub-directories are found. set by default.

output_image

the name of output spritemap image. sprite_dirs is incompatible with this because both tell the spritemapper how to sort sprites into spritemaps. by default <dir> + .png.

output_css

the name for the rewritten CSS file. by default sm_{basename}{extension}.

padding

amount of padding space between two images. this is mostly useful to counteract subpixel rendering artifacts on iOS devices. by default 1.

anneal_steps

a larger number here makes the box packer algorithm try more combinations. by default 9200.

Running tests

The test suite requires Nose. You can run them through setup.py, python setup.py test or plain nosetests.