...
rule getValue is active {
select when pageview ".*" setting ()
pre {
image = <<data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg==>>;
base64EncodedDatamimetype = AWSS3:getType(image);
// Evaluates to image/png
...