035-optipng.Rmd

This demos shows you how to optimize PNG images with `optipng`.

```{r setup}
opts_chunk$set(cache=TRUE)
knit_hooks$set(optipng = hook_optipng)
```

Now we set the chunk option `optipng` to a non-`NULL` value, e.g. `''`, to activate the hook.

```{r use-optipng, optipng=''}
library(ggplot2)
set.seed(123)
qplot(rnorm(1e3), rnorm(1e3))
```

Same plot, not optimized:

```{r no-optipng, ref.label='use-optipng'}
```

Same plot, most heavily optimized (pass `-o7` to `optipng`):

```{r optipng-o7, ref.label='use-optipng', optipng='-o7'}
```