agg_record: Capture drawing instructions without rendering

In ragg: Graphic Devices Based on AGG

Capture drawing instructions without rendering

Description

While the point of a graphics device is usually to render the graphics, there are a few situations where you are instead interested in only capturing the instructions required to render the graphics. While all graphics devices can be retrofitted for that using dev.control(), they would still render to their internal buffer even if you are only interested in the recorded instructions, thus adding a performance penalty. agg_record() is a device that does no rendering whatsoever, but has recording turned on by default making it a no-overhead solution for plot recording.

Usage

agg_record(
  width = 480,
  height = 480,
  units = "px",
  pointsize = 12,
  background = "white",
  res = 72,
  scaling = 1,
  snap_rect = TRUE,
  bg
)

Arguments

width, height	The dimensions of the device
units	The unit width and height is measured in, in either pixels ('px'), inches ('in'), millimeters ('mm'), or centimeter ('cm').
pointsize	The default pointsize of the device in pt. This will in general not have any effect on grid graphics (including ggplot2) as text size is always set explicitly there.
background	The background colour of the device
res	The resolution of the device. This setting will govern how device dimensions given in inches, centimeters, or millimeters will be converted to pixels. Further, it will be used to scale text sizes and linewidths
scaling	A scaling factor to apply to the rendered line width and text size. Useful for getting the right dimensions at the resolution that you need. If e.g. you need to render a plot at 4000x3000 pixels for it to fit into a layout, but you find that the result appears to small, you can increase the scaling argument to make everything appear bigger at the same resolution.
snap_rect	Should axis-aligned rectangles drawn with only fill snap to the pixel grid. This will prevent anti-aliasing artifacts when two rectangles are touching at their border.
bg	Same as background for compatibility with old graphic device APIs

Examples

# Capture drawing instructions
agg_record()
plot(1:10, 1:10)
rec <- recordPlot()
dev.off()

# Replay these on another device
file <- tempfile(fileext = '.png')
agg_png(file)
replayPlot(rec)
dev.off()

ragg documentation built on April 12, 2025, 1:23 a.m.