agg_png {ragg}

Draw to a PNG file

Description

The PNG (Portable Network Graphic) format is one of the most ubiquitous today, due to its versatiliity and widespread support. It supports transparency as well as both 8 and 16 bit colour. The device uses default compression and filtering and will not use a colour palette as this is less useful for antialiased data. This means that it might be possible to compress the resulting image even more if size is of concern (though the defaults are often very good). In contrast to grDevices::png() the date and time will not be written to the file, meaning that similar plot code will produce identical files (a good feature if used with version control). It will, however, write in the dimensions of the image based on the res argument.

Usage

agg_png(
  filename = "Rplot%03d.png",
  width = 480,
  height = 480,
  units = "px",
  pointsize = 12,
  background = "white",
  res = 72,
  scaling = 1,
  snap_rect = TRUE,
  bitsize = 8,
  bg
)

Arguments

filename

The name of the file. Follows the same semantics as the file naming in grDevices::png(), meaning that you can provide a sprintf() compliant string format to name multiple plots (such as the default value)

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.

bitsize

Should the device record colour as 8 or 16bit

bg

Same as background for compatibility with old graphic device APIs

Examples

file <- tempfile(fileext = '.png')
agg_png(file)
plot(sin, -pi, 2*pi)
dev.off()