def compute_image_positions!
case layout
when SMART
require 'compass/sass_extensions/sprites/layout/smart'
@images, @width, @height = Layout::Smart.new(@images, @kwargs).properties
when DIAGONAL
require 'compass/sass_extensions/sprites/layout/diagonal'
@images, @width, @height = Layout::Diagonal.new(@images, @kwargs).properties
when HORIZONTAL
require 'compass/sass_extensions/sprites/layout/horizontal'
@images, @width, @height = Layout::Horizontal.new(@images, @kwargs).properties
else
require 'compass/sass_extensions/sprites/layout/vertical'
@images, @width, @height = Layout::Vertical.new(@images, @kwargs).properties
end
end