Extract a logo resource from a brand — brand_use

Returns a brand logo resource specified by name and variant from a brand object. The image paths in the returned object are adjusted to be absolute, relative to the location of the brand YAML file, if brand was read from a file, or the local working directory otherwise.

Usage

brand_use_logo(
  brand,
  name,
  variant = c("auto", "light", "dark", "light-dark"),
  ...,
  .required = !name %in% c("small", "medium", "large", "smallest", "largest"),
  .allow_fallback = TRUE
)

Arguments

brand

A brand object from read_brand_yml() or as_brand_yml().

name

The name of the logo to use. Either a size ("small", "medium", "large") or an image name from brand.logo.images. Alternatively, you can also use "smallest" or "largest" to select the smallest or largest available logo size, respectively.

variant

Which variant to use, only used when name is one of the brand.yml fixed logo sizes ("small", "medium", or "large"). Can be one of:

"auto": Auto-detect, returns a light/dark logo resource if both variants are present, otherwise it returns a single logo resource, either the value for brand.logo.{name} or the single light or dark variant if only one is present.
"light": Returns only the light variant. If no light variant is present, but brand.logo.{name} is a single logo resource and allow_fallback is TRUE, brand_use_logo() falls back to the single logo resource.
"dark": Returns only the dark variant, or, as above, falls back to the single logo resource if no dark variant is present and allow_fallback is TRUE.
"light-dark": Returns a light/dark object with both variants. If a single logo resource is present for brand.logo.{name} and allow_fallback is TRUE, the single logo resource is promoted to a light/dark logo resource with identical light and dark variants.

...

Additional named attributes to be added to the image HTML or markdown when created via format(), knitr::knit_print(), or htmltools::as.tags().

.required

Logical or character string. If TRUE, an error is thrown if the requested logo is not found. If a string, it is used to describe why the logo is required in the error message and completes the phrase "is required ____". Defaults to FALSE when name is one of the fixed sizes – "small", "medium", "large" or "smallest" or "largest". Otherwise, an error is thrown by default if the requested logo is not found.

.allow_fallback

If TRUE (the default), allows falling back to a non-variant-specific logo when a specific variant is requested. Only used when name is one of the fixed logo sizes ("small", "medium", or "large").

Value

A brand_logo_resource object, a brand_logo_resource_light_dark object, or NULL if the requested logo doesn't exist and .required is FALSE.

Shiny apps and HTML documents

You can use brand_use_logo() to include logos in Shiny apps or in HTML documents produced by Quarto or R Markdown.

In Shiny apps, logos returned by brand_use_logo() will automatically be converted into HTML tags using htmltools::as.tags(), so you can include them directly in your UI code.

library(shiny)
library(bslib)

brand <- read_brand_yml()

ui <- page_navbar(
  title = tagList(
    brand_use_logo(brand, "small"),
    "Brand Use Logo Test"
  ),
  nav_panel(
    "Page 1",
    card(
      card_header("My Brand"),
      brand_use_logo(brand, "medium", variant = "dark")
    )
  )
  # ... The rest of your app
)

If your brand includes a light/dark variant for a specific size, both images will be included in the app, but only the appropriate image will be shown based on the user's system preference of the app's current theme mode if you are using bslib::input_dark_mode().

To include additional classes or attributes in the <img> tag, you can call htmltools::as.tags() directly and provide those attributes:

brand <- as_brand_yml(list(
  logo = list(
    images = list(
      "cat-light" = list(
        path = "https://placecats.com/louie/300/300",
        alt = "A light-colored tabby cat on a purple rug"
      ),
      "cat-dark" = list(
        path = "https://placecats.com/millie/300/300",
        alt = "A dark-colored cat looking into the camera"
      ),
      "cat-med" = "https://placecats.com/600/600"
    ),
    small = list(light = "cat-light", dark = "cat-dark"),
    medium = "cat-med"
  )
))

brand_use_logo(brand, "small") |>
  htmltools::as.tags(class = "my-logo", height = 32)

The same applies to HTML documents produced by Quarto or R Markdown, where images can be used in-line:

```{r}
brand_use_logo(brand, "small")
```

This is my brand's medium sized logo: `r brand_use_logo(brand, "medium")`

Finally, you can use format() to convert the logo to raw HTML or markdown:

cat(format(brand_use_logo(brand, "small", variant = "light")))
#> <img src="https://placecats.com/louie/300/300" alt="A light-colored tabby cat on a purple rug" class="brand-logo"/>

cat(format(
  brand_use_logo(brand, "medium"),
  .format = "markdown",
  class = "my-logo",
  height = 500
))
#> ![](https://placecats.com/600/600){.brand-logo .my-logo alt="" height="500"}

Examples

brand <- as_brand_yml(list(
  logo = list(
    images = list(
      small = "logos/small.png",
      huge = list(path = "logos/huge.png", alt = "Huge Logo")
    ),
    small = "small",
    medium = list(
      light = list(
        path = "logos/medium-light.png",
        alt = "Medium Light Logo"
      ),
      dark = list(path = "logos/medium-dark.png")
    )
  )
))

brand_use_logo(brand, "small")
#> <brand_logo_resource src="./logos/small.png" alt="">
brand_use_logo(brand, "medium")
#> <brand_logo_resource src="./logos/medium-light.png" alt="Medium Light Logo" variant="light">
#> <brand_logo_resource src="./logos/medium-dark.png" alt="" variant="dark">
brand_use_logo(brand, "large")
#> NULL
brand_use_logo(brand, "huge")
#> <brand_logo_resource src="./logos/huge.png" alt="Huge Logo">

brand_use_logo(brand, "small", variant = "light")
#> <brand_logo_resource src="./logos/small.png" alt="">
brand_use_logo(brand, "small", variant = "light", allow_fallback = FALSE)
#> <brand_logo_resource src="./logos/small.png" alt="" allow_fallback="false">
brand_use_logo(brand, "small", variant = "light-dark")
#> <brand_logo_resource src="./logos/small.png" alt="" variant="light">
#> <brand_logo_resource src="./logos/small.png" alt="" variant="dark">
brand_use_logo(
  brand,
  "small",
  variant = "light-dark",
  allow_fallback = FALSE
)
#> <brand_logo_resource src="./logos/small.png" alt="" variant="light">
#> <brand_logo_resource src="./logos/small.png" alt="" variant="dark">

brand_use_logo(brand, "medium", variant = "light")
#> <brand_logo_resource src="./logos/medium-light.png" alt="Medium Light Logo">
brand_use_logo(brand, "medium", variant = "dark")
#> <brand_logo_resource src="./logos/medium-dark.png" alt="">
brand_use_logo(brand, "medium", variant = "light-dark")
#> <brand_logo_resource src="./logos/medium-light.png" alt="Medium Light Logo" variant="light">
#> <brand_logo_resource src="./logos/medium-dark.png" alt="" variant="dark">