Feature request: fig.alt as a chunk option #1867

mdogucu · 2020-07-20T01:24:29Z

In addition to using ![alt text][id] to write alt text it would be very useful to have fig.alt option for code chunks that could write the alt text for a figure. Unfortunately, with the current state of things, the figure caption and alt text is the same when used in code chunk. Thus, when using a screen reader only figure caption is read by the screen reader. However, for visually impaired readers, often further description of an image is needed. An example of what I have on my mind is provided below with modifications to the code provided in the R Markdown book:

```{r mtcars, fig.cap = "Another amazing plot", fig.alt = "The scatter plot has hp on the x axis and mpg on the y axis. The points show a negative trend but the plot does not include a line of best fit."}
plot(mpg ~ hp, mtcars)
```

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cderv · 2020-07-20T07:04:13Z

About this topic, here is a chapter about accessibility in the next Rmarkdown book: https://bookdown.org/yihui/rmarkdown-cookbook/html-accessibility.html Your insights could be useful as we are not expert on this.
It comes from a discussion in rstudio/rmarkdown-cookbook#242

And yes currently, the caption and alt text are the same, and you can only have the alt text and not show the caption. But I don't think they can be different right now.
This is a feature request for knitr to add this chunk option. I think it could be a good idea and this seems important

AmeliaMN · 2020-07-20T15:29:38Z

Just here to put in another voice of support for this feature! Accessibility is important, so it should be easy for users to make things accessible. When I was working on my useR! talk I was trying to do the same thing. I think a chunk option is the way to go, and was surprised to see it didn't exist already.

cderv · 2020-07-20T16:37:03Z

I just opened an issue in knitr for adding a fig.alt chunk option. This must be done there and it is knitr code that we need to make this feasible.

jooyoungseo · 2020-10-25T19:39:36Z

Yes, let me vote for this feature request as an actual screen-reader user.

Currently, there is no way for users to create alt text and figure caption separately for graphs.

While figure caption is used for a relatively concise figure title, image alt text is intended to deliver more descriptive text-based information for assistive technologies (e.g., screen readers).

In the following example, you may understand the usage of auto-generated alt text, which should be different from fig.cap.

Ideally, I also want to give the figure a concise fig.cap like "Bar chart of clas" while attaching the alt text value to img$alt.

```{r g-alt, fig.cap = caption}
    # Make a simple graph
    library(tidyverse)

    g <- mpg %>%
      ggplot(aes(class)) +
      geom_bar()

    # Create alt text using BrailleR package
    if (!require(BrailleR)) {
      remotes::install_github("ajrgodfrey/BrailleR")
    }

    library(BrailleR)
    #;-) The BrailleR.View,  option is set to FALSE.
    #;-) 
    #;-) Attaching package: 'BrailleR'
    #;-) The following objects are masked from 'package:ggplot2':
    #;-) 
    #;-)     xlab, ylab
    #;-) The following objects are masked from 'package:graphics':
    #;-) 
    #;-)     boxplot, hist
    #;-) The following object is masked from 'package:utils':
    #;-) 
    #;-)     history
    #;-) The following objects are masked from 'package:base':
    #;-) 
    #;-)     grep, gsub

    caption <- paste(capture.output(BrailleR::VI(g)), collapse = " ")
    g
```

Result

![This is an untitled chart with no subtitle or caption. It has x-axis ‘class’ with labels . It has y-axis ‘count’ with labels . The chart is a bar chart containing 7 vertical bars. Bar 1 is centered horizontally at 2seater, and spans vertically from 0 to 5. Bar 2 is centered horizontally at compact, and spans vertically from 0 to 47. Bar 3 is centered horizontally at midsize, and spans vertically from 0 to 41. Bar 4 is centered horizontally at minivan, and spans vertically from 0 to 11. Bar 5 is centered horizontally at pickup, and spans vertically from 0 to 33. Bar 6 is centered horizontally at subcompact, and spans vertically from 0 to 35. Bar 7 is centered horizontally at suv, and spans vertically from 0 to 62.](https://i.imgur.com/t47e9BZ.png)