with_displacement {ggfx}

Apply a displacement map to a layer

Description

This filter displaces the pixels based on the colour values of another layer or raster object. As such it can be used to distort the content of the layer.

Usage

with_displacement(x, x_map, y_map = x_map, x_scale = 1, y_scale = x_scale, ...)

Arguments

x

A ggplot2 layer object, a ggplot, a grob, or a character string naming a filter

x_map, y_map

The displacement maps to use. Can either be a string identifying a registered filter, or a raster object. The maps will be resized to match the dimensions of x. Only one channel will be used - see the docs on channels for info on how to set them.

x_scale, y_scale

How much displacement should a maximal channel value correspond to? If a numeric it will be interpreted as pixel dimensions. If a unit object it will be converted to pixel dimension when rendered.

...

Arguments to be passed on to methods. See the documentation of supported object for a description of object specific arguments.

Value

Depending on the input, either a grob, Layer, list of Layers, guide, or element object. Assume the output can be used in the same context as the input.

Examples

library(ggplot2)
ggplot() +
  as_reference(
    geom_polygon(aes(c(0, 1, 1), c(0, 0, 1)), colour = NA, fill = 'magenta' ),
    id = "displace_map"
  ) +
  with_displacement(
    geom_text(aes(0.5, 0.5, label = 'Displacements!'), size = 10),
    x_map = ch_red("displace_map"),
    y_map = ch_blue("displace_map"),
    x_scale = unit(0.025, 'npc'),
    y_scale = unit(0.025, 'npc')
  )