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Mar 4, 2011

Css sprite generation

Vladimir Sidorenko
Vladimir Sidorenko

I've created this small sprite to create css sprites. It glues images from directory directory into single file and generates corresponding css.

#!/usr/bin/python

import os
import os.path as p
import Image


css_inline_item_template = '''
%(selector)s {
    background: url(%(url)s) no-repeat -%(xpos)spx -%(ypos)spx;
    width: %(width)spx;
    height: %(height)spx;
}
'''

css_base_template = '''
%(base_selector)s {
    background-image: url(%(url)s);
    background-repeat: no-repeat;
}
'''

css_base_item_template = '''
%(selector)s {
    background-position: -%(xpos)spx -%(ypos)spx;
    width: %(width)spx;
    height: %(height)spx;
}
'''


def generate_sprite(images, margin=10):
    def _basename(path):
        return p.splitext(p.basename(path))[0]

    data = []

    master_height = max(*[i.size[1] for i in images])
    master_width = sum([i.size[0] for i in images]) + margin * (len(images) - 1)

    sprite = Image.new(
        mode='RGBA',
        size=(master_width, master_height),
        color=(0,0,0,0))  # fully transparent

    location = 0
    for image in images:
        if 'transparency' in image.info:
            raise Exception('Incorrect transparency mode: ' + image.filename)

        sprite.paste(image,(location, 0))
        data.append({
            'xpos': location,
            'ypos': 0,
            'dir': _basename(p.dirname(image.filename)),
            'file': _basename(image.filename),
            'width': image.size[0],
            'height': image.size[1],
        })
        location += image.size[0] + margin

    return sprite, data

def render_css(base_template, item_template, css_data, sprite_url, base_selector, selector):
    base_info = {
        'base_selector': base_selector,
        'url': sprite_url,
    }
    base_css = base_template % base_info

    items_css = '\n'.join([
        item_template % dict([('selector', selector % image_data)]
            + image_data.items()
            + base_info.items())
        for image_data in css_data])

    return base_css + items_css

def create_sprite_and_css(images_dir, css_output, sprite_output,
        selector='.%(file)s', base_selector='.sprite', url=None, inline=False):
    images = [Image.open(p.join(images_dir, filename))
                for filename in os.listdir(images_dir)
                if not filename.startswith('.')]

    sprite, css_data = generate_sprite(images)
    sprite.save(sprite_output)

    sprite_url = url or p.basename(sprite_output)
    if inline:
        css = render_css('', css_inline_item_template, css_data, sprite_url, base_selector, selector)
    else:
        css = render_css(css_base_template, css_base_item_template, css_data, sprite_url, base_selector, selector)

    css_file = open(css_output, 'w')
    css_file.write(css)
    css_file.close()


if __name__ == '__main__':
    from optparse import OptionParser

    usage = "usage: %prog [options] images_dir css_output sprite_output"
    parser = OptionParser(usage=usage)
    parser.add_option("-i", "--inline", action="store_true", dest="inline", default=False,
                      help="When set, image url will be put in css rule for every item.")
    parser.add_option("-s", "--selector", dest="selector", default='.%(file)s',
                      help="Selector template. You can use dir, file, width, height here.")
    parser.add_option("-S", "--base-selector", dest="base_selector", default='.sprite',
                      help="Base selector template for base css rule (when -i is not set).")
    parser.add_option("-u", "--url", dest="url", default='',
                      help="Css rule Image url template.")

    (options, args) = parser.parse_args()

    if len(args) < 3:
        print 'You must provide all 3 arguments.'
    else:
        images_dir, css_output, sprite_output = [p.realpath(arg) for arg in args]
        create_sprite_and_css(images_dir, css_output, sprite_output,
                selector=options.selector,
                base_selector=options.base_selector,
                inline=options.inline,
                url=options.url)

Update

This article is pretty old. Now it's better to use something integrated to your build process, like grunt or webassets.

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