agg_jpeg {ragg}

Draw to a JPEG file

Description

The JPEG file format is a lossy compressed file format developed in particular for digital photography. The format is not particularly well-suited for line drawings and text of the type normally associated with statistical plots as the compression algorithm creates noticable artefacts. It is, however, great for saving image data, e.g. heightmaps etc. Thus, for standard plots, it would be better to use agg_png(), but for plots that includes a high degree of raster image rendering this device will result in smaller plots with very little quality degradation.

Usage

agg_jpeg(
  filename = "Rplot%03d.jpeg",
  width = 480,
  height = 480,
  units = "px",
  pointsize = 12,
  background = "white",
  res = 72,
  scaling = 1,
  snap_rect = TRUE,
  quality = 75,
  smoothing = FALSE,
  method = "slow",
  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.

quality

An integer between 0 and 100 defining the quality/size tradeoff. Setting this to 100 will result in no compression.

smoothing

A smoothing factor to apply before compression, from 0 (no smoothing) to 100 (full smoothing). Can also by FALSE (no smoothing) or TRUE (full smoothing).

method

The compression algorithm to use. Either 'slow', 'fast', or 'float'. Default is 'slow' which works best for most cases. 'fast' should only be used when quality is below 97 as it may result in worse performance at high quality settings. 'float' is a legacy options that calculate the compression using floating point precission instead of with integers. It offers no quality benefit and is often much slower.

bg

Same as background for compatibility with old graphic device APIs

Note

Smoothing is only applied if ragg has been compiled against a jpeg library that supports smoothing.

Examples

file <- tempfile(fileext = '.jpeg')
agg_jpeg(file, quality = 50)
plot(sin, -pi, 2*pi)
dev.off()