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module Banzai
module Filter
# HTML filter that moves the value of image `src` attributes to `data-src`
# so they can be lazy loaded.
class ImageLazyLoadFilter < HTML::Pipeline::Filter
def call
doc.xpath('descendant-or-self::img').each do |img|
img['class'] ||= '' << 'lazy'
unless img['src'].nil? || img['src'].empty?
img['data-src'] = img['src']
img['src'] = LazyImageTagHelper.placeholder_image
begin
url = URI.parse(img['data-src'])
unless url.nil? || url.query.nil?
size_parameters = CGI.parse(url.query)
unless size_parameters['w'].empty? || size_parameters['h'].empty?
img_width = size_parameters['w'].first.to_i
img_height = size_parameters['h'].first.to_i
if img_width > 0 && img_height > 0
img['width'] = img_width
img['height'] = img_height
img['class'] << 'lazy-sized'
# We need to have a container around with actual aspect_ratio set to support responsive img's
if img.parent.name == 'a'
img.parent.style = '' << calculate_aspect_ratio(img_width, img_height)
else
img_container = doc.document.create_element(
'span',
class: 'rimg-container',
style: calculate_aspect_ratio(img_width, img_height)
)
img_container.children = img.clone
img.replace(img_container)
end
end
end
end
rescue URI::InvalidURIError
end
end
end
doc
end
def calculate_aspect_ratio(img_width, img_height)
if img_width > img_height
aspect_ratio = img_height / (img_width * 0.01)
"height:0;padding-bottom:#{aspect_ratio}%"
else
aspect_ratio = img_width / (img_height * 0.01)
"width:0;padding-right:#{aspect_ratio}%"
end
end
end
end
end
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