age</a> which makes it relatively easy to use them in conjunction with ggplot2. Phrased in the most general terms, a filter is any function that takes one image as input and returns a new (presumably modified!) image as output. As an example, think about how Instagram filters work: the original photo is used as the input, and the modified one is returned as output. This filtering takes place at the pixel level, so it’s not immediately obvious how we could do this with ggplot2. The way that the ggfx packag