image: Create or write image

imageR Documentation

Create or write image

Description

If you have V8, withr, and fs installed, you can use these functions can to create or write images as PNG or SVG, using a vegaspec or vegawidget. To convert to a bitmap, or write a PNG file, you will additionally need the rsvg and png packages.

Usage

vw_to_svg(spec, width = NULL, height = NULL, base_url = NULL, seed = NULL)

vw_to_bitmap(spec, scale = 1, width = NULL, height = NULL, ...)

vw_write_svg(spec, path, width = NULL, height = NULL, ...)

vw_write_png(spec, path, scale = 1, width = NULL, height = NULL, ...)

Arguments

spec

An object to be coerced to vegaspec, a Vega/Vega-Lite specification

width

integer, if specified, the total rendered width (in pixels) of the chart - valid only for single-view charts and layered charts; the default is to use the width in the chart specification

height

integer, if specified, the total rendered height (in pixels) of the chart - valid only for single-view charts and layered charts; the default is to use the height in the chart specification

base_url

character, the base URL for a data file, useful for specifying a local directory; defaults to an empty string

seed

integer, the random seed for a Vega specification, defaults to a "random" integer

scale

numeric, useful for specifying larger images supporting the increased-resolution of retina displays

...

additional arguments passed to vw_to_svg()

path

character, local path to which to write the file

Details

These functions can be called using (an object that can be coerced to) a vegaspec.

The scripts used are adapted from the Vega command line utilities.

Value

vw_to_svg()

character, SVG string

vw_to_bitmap()

array, bitmap array

vw_write_svg()

invisible vegaspec or vegawidget, called for side-effects

vw_write_png()

invisible vegaspec or vegawidget, called for side-effects

See Also

vega-view library

Examples

  # call any of these functions using either a vegaspec or a vegawidget
  svg <- vw_to_svg(vegawidget(spec_mtcars))
  bmp <- vw_to_bitmap(spec_mtcars)
  vw_write_png(spec_mtcars, file.path(tempdir(), "temp.png"))
  vw_write_svg(spec_mtcars, file.path(tempdir(), "temp.svg"))

  # To specify the path to a local file, use base_url
  spec_precip <-
    list(
      `$schema` = vega_schema(),
      data = list(url = "seattle-weather.csv"),
      mark = "tick",
      encoding = list(
        x = list(field = "precipitation", type = "quantitative")
      )
    ) %>%
    as_vegaspec()

  data_dir <- system.file("example-data/", package = "vegawidget")
  vw_write_png(
    spec_precip,
    file.path(tempdir(), "temp-local.png"),
    base_url = data_dir
  )


vegawidget documentation built on May 29, 2024, 12:17 p.m.