Pdf and Html output

Hello everyone, I have a question.
A topic has an image with a size, but I want to get it by pdf with a size and by html5 with another size, is it possible?

Currently this image is inside a div class, would it be possible from the css to use an IF function that is to say if I take out the topic by pdf has a size and by html another? I would not like to have to duplicate outputs.
Thanks