mixin img(name, ext, alt)
img(srcset='img/#{name}.#{ext},img/#{name}@2x.#{ext} 1.5x,img/#{name}@2x.#{ext} 2x', src='img/#{name}.#{ext}', alt='!={alt}')
+img('sail','jpg', 'alt text')
<img srcset="img/#{name}.#{ext},img/#{name}@2x.#{ext} 1.5x,img/#{name}@2x.#{ext} 2x" src="img/#{name}.#{ext}" alt="#{alt}">