alt_check: Check for Problems with the Alt Text for Images on a Web Page

In matt-dray/altcheckr: Assess Image Alt Text on a Web Page

Description

Infer whether an image's alt tag is missing or could be improved.

Usage

alt_check(
  attributes_df,
  max_char = 125,
  min_char = 20,
  file_ext = ".jpg$|.jpeg$|.png$|.svg$|.gif$",
  redundant_pattern = "image|picture|photo|graph|plot|diagram"
)

Arguments

attributes_df	A data.frame/tibble with image attributes, produced by alt_get.
max_char	A numeric value. Alt text longer than this is flagged.
min_char	A numeric value. Alt text shorter than this is flagged.
file_ext	A character string. A regular expression of image file extensions.
redundant_pattern	A character string. A regular expression of 'redundant' phrases in alt text.

Value

A tibble object with classes tbl_df, tbl and data.frame. In addition to columns provided by alt_get, also returns:

• alt_exists "Exists", "Missing" or intentionally "Empty".

• nchar_count Integer. Number of characters.

• nchar_assess "Short", "Long" or "OK", depending on inputs to min_char and max_char.

• file_ext Logical. Does it look like the alt text might just be a filename (e.g. ends with ".jpg")?

• self_evident Logical. Is a redundant phrase used in the alt text (e.g. "a picture of")?

• terminal_punct Logical. Does the alt text end with terminal punctuation, like a period, to allow a screen reader to parse it as a sentence?

• spellcheck Character. Words to check for misspelling. These could be misread by a screenreader.

• not_basic Character list column. Words that match to the 850 words of Charles Kay Ogden's Basic English.

Examples

## Not run: 
    url <- "https://alphagov.github.io/accessibility-tool-audit/test-cases.html#images"
    attr_df <- alt_get(url)
    alt_check(attr_df)
    
## End(Not run)

matt-dray/altcheckr documentation built on Jan. 21, 2021, 8:02 a.m.