local_image: Helper function for adding a local image

In rstudio/gt: Easily Create Presentation-Ready Display Tables

Helper function for adding a local image

Description

We can flexibly add a local image (i.e., an image residing on disk) inside of a table with local_image() function. The function provides a convenient way to generate an HTML fragment using an on-disk PNG or SVG. Because this function is currently HTML-based, it is only useful for HTML table output. To use this function inside of data cells, it is recommended to use text_transform() first. With that function, we can specify which data cells to target and then include a local_image() call within the required user-defined function (for the fn argument). If we want to include an image in other places (e.g., in the header, within footnote text, etc.) we need to use local_image() within the html() helper function.

By itself, the function creates an HTML image tag with an image URI embedded within. We can easily experiment with a local PNG or SVG image that's available in the gt package using the test_image() function. Using that, the call local_image(file = test_image(type = "png")) evaluates to:

⁠<img src=<data URI> style=\"height:30px;\">⁠

where a height of ⁠30px⁠ is a default height chosen to work well within the heights of most table rows.

Usage

local_image(filename, height = 30)

Arguments

filename	Path to image file ⁠scalar<character>⁠ // required A local path to an image file on disk.
height	Height of image ⁠scalar<numeric|integer>⁠ // default: 30 The absolute height of the image in the table cell (in "px" units). By default, this is set to "30px".

Value

A character object with an HTML fragment that can be placed inside of a cell.

Examples

Create a tibble that contains heights of an image in pixels (one column as a string, the other as numerical values), then, create a gt table. Use text_transform() to insert a local test image (PNG) image with the various sizes.

dplyr::tibble(
  pixels = px(seq(10, 35, 5)),
  image = seq(10, 35, 5)
) |>
  gt() |>
  text_transform(
    locations = cells_body(columns = image),
    fn = function(x) {
      local_image(
        filename = test_image(type = "png"),
        height = as.numeric(x)
      )
    }
  )

Function ID

9-2

Function Introduced

v0.2.0.5 (March 31, 2020)

See Also

Other image addition functions: ggplot_image(), test_image(), web_image()

rstudio/gt documentation built on Nov. 2, 2024, 5:53 p.m.