Suppress alt text for GIFs in rmarkdown HTML output - r

Question

I'm generating GIFs using the gganimate package within an RMarkdown file. When using output = github_document in the front matter, the GIF appears as expected in the output (github-document-output). However, when using output = html_document, the GIF generates with alt text, which defaults to the chunk name (html-document-output).
Is there a way to suppress this automatic caption? I've tried setting my own caption using the fig.cap chunk option, but that was unsuccessful.
RMarkdown code
---
output:
html_document: default
github_document: default
---
```{r}
knitr::opts_chunk$set(
collapse = TRUE,
comment = "#>",
fig.path = "output/test-fig-",
cache.path = "output/test-cache-"
)
```
```{r cache = FALSE}
library(knitr)
library(animation)
ani.options(autobrowse = FALSE, interval = 1)
opts_knit$set(animation.fun = function(x, options, format = "gif") {
x = c(knitr:::sans_ext(x), knitr:::file_ext(x))
fig.num = options$fig.num
format = sub("^[.]", "", format)
fig.fname = paste0(sub(paste0(fig.num, "$"), "*", x[1]),
".", x[2])
mov.fname = paste0(sub(paste0(fig.num, "$"), "", x[1]), ".",
format)
# order correctly
figs <- Sys.glob(fig.fname)
figs <- figs[order(as.numeric(stringr::str_match(figs, paste0("(\\d+)\\.", x[2]))[, 2]))]
animation::im.convert(figs, output = mov.fname)
sprintf("![%s](%s)", options$label, paste0(opts_knit$get("base.url"), mov.fname))
})
opts_chunk$set(cache = TRUE, message = FALSE, warning = FALSE, fig.show = "animate")
```
```{r pkgs, cache = FALSE}
library(gapminder)
library(ggplot2)
theme_set(theme_bw())
```
```{r setup}
p <- ggplot(gapminder, aes(gdpPercap, lifeExp, size = pop, color = continent, frame = year)) +
geom_point() +
scale_x_log10()
```
```{r dependson = "setup"}
library(gganimate)
gg_animate(p)
```

Answer 1

The problem here is that you include the resulting animation with markdown syntax. This introduces some iiritations I guess.
Taking a look at hook_plot_html we can simulate the default output for standard plots:
sprintf(paste0('<div class="figure %s">',
'<img src="%s">',
'<p class="caption">%s</p>',
'</div>'), options$fig.align, mov.fname, options$fig.cap)