web_image: Helper function for adding an image from the web

Description

We can flexibly add a web image inside of a table with web_image() function. The function provides a convenient way to generate an HTML fragment with an image URL. 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 that the text_transform() function is used. With that function, we can specify which data cells to target and then include a web_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 web_image() within the html() helper function.

Usage

web_image(url, height = 30)

Value

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

Arguments

url: A url that resolves to an image file.
height: The absolute height (px) of the image in the table cell.

Examples

Get the PNG-based logo for the R Project from an image URL.

r_png_url <- "https://www.r-project.org/logo/Rlogo.png"

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 the text_transform() function to insert the R logo 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) {
      web_image(
        url = r_png_url,
        height = as.numeric(x)
      )
    }
  )

This image of a table was generated from the first code example in the `web_image()` help file.

Get the SVG-based logo for the R Project from an image URL.

r_svg_url <- "https://www.r-project.org/logo/Rlogo.svg"

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 the tab_header() function to insert the R logo SVG image once in the title and five times in the subtitle.

dplyr::tibble(
  pixels = px(seq(10, 35, 5)),
  image = seq(10, 35, 5)
) %>%
  gt() %>%
  tab_header(
    title = html(
      "<strong>R Logo</strong>",
      web_image(
        url = r_svg_url,
        height = px(50)
      )
    ),
    subtitle = html(
      web_image(
        url = r_svg_url,
        height = px(12)
      ) %>%
        rep(5)
    )
  )

This image of a table was generated from the second code example in the `web_image()` help file.

Function ID

8-1

Details

By itself, the function creates an HTML image tag, so, the call web_image("http://example.com/image.png") evaluates to:

<img src=\"http://example.com/image.png\" style=\"height:30px;\">

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