UI Appearance testing tool?

I am looking for tools to web applications UI testing. I know that there are many tools like Selenium and similar, but I am looking something for testing UI appearance, not UI behavior. I do not want to test if correct form shows in correct moment. I would like to test charts, graphics and animations.

Example Let assume that I have web application with complex animations created using d3.js. I would like to test appearance with accuracy at the level of individual pixels: size, distance, colors of individual elements, transitions time and even singular frames.

I do not know if it is sensible approach? Do you know of such a tool?