Using resmush

resmush is an R package for optimizing and compressing images with reSmush.it. reSmush.it is a free API for image optimization and is available through WordPress and many other tools.

reSmush.it includes:

Free image optimization with no API key required.
Support for local and online images.
Support for png, jpg/jpeg, gif, bmp and tiff files.
Maximum image size: 5 MB.
Compression powered by several algorithms:
- PNGQuant: Removes unnecessary chunks from png files while preserving full alpha transparency.
- JPEGOptim: Lossless optimization based on Huffman table optimization.
- OptiPNG: A png optimizer used by several online compression tools.

Example

Compress an online jpg image with resmush_url():

library(resmush)

url <- "https://dieghernan.github.io/resmush/img/jpg_example_original.jpg"

resmush_url(url, outfile = "jpg_example_compress.jpg", overwrite = TRUE)
#> ══ resmush summary ═════════════════════════════════════════════════════════════
#> ℹ Input: 1 URL, total size 178.7 Kb.
#> ✔ Optimized 1 URL: Size is now 45 Kb (was 178.7 Kb). Saved 133.7 Kb (74.82%).
#> Saved result in directory '.'.

Use the qlty argument to adjust compression quality for jpg files. Keep this value above 90 to maintain good image quality.

# Use an extreme compression setting.
resmush_url(
  url,
  outfile = tempfile(fileext = ".jpg"),
  overwrite = TRUE,
  qlty = 3
)
#> ══ resmush summary ═════════════════════════════════════════════════════════════
#> ℹ Input: 1 URL, total size 178.7 Kb.
#> ✔ Optimized 1 URL: Size is now 2.2 Kb (was 178.7 Kb). Saved 176.4 Kb (98.74%).
#> Saved result in directory 'tempdir()'.

JPEG image with visible compression artifacts — Figure 2: Image with visible compression artifacts caused by high compression (`qlty = 3`), compared with Figure 1 (b).

All optimization functions invisibly return a data frame that summarizes the process. The following example shows this output when compressing a local file:

png_file <- system.file("extimg/example.png", package = "resmush")

# Copy to a temporary file for this example.
tmp_png <- tempfile(fileext = ".png")
file.copy(png_file, tmp_png, overwrite = TRUE)
#> [1] TRUE

summary <- resmush_file(tmp_png, overwrite = TRUE)

tibble::as_tibble(summary[, -c(1, 2)])
#> # A tibble: 1 × 6
#>   src_size dest_size compress_ratio notes src_bytes dest_bytes
#>   <chr>    <chr>     <chr>          <chr>     <dbl>      <dbl>
#> 1 239.9 Kb 70.7 Kb   70.54%         OK       245618      72356

Alternatives

Several other R packages also provide image optimization tools:

The xfun package (Xie 2024), which includes:
- xfun::tinify(): Similar to resmush_file() but uses TinyPNG and requires an API key.
- xfun::optipng(): Compresses local files using OptiPNG, which must be installed locally.
The tinieR package by jmablog: An R interface to TinyPNG.
The tinyimg package (Xie 2026): Optimizes local png and jpg/jpeg files using Rust libraries.
The optout package by @coolbutuseless: Similar to xfun::optipng() but with more options. Requires additional local software.

Tool	CRAN	Additional software	Online images	API key required	Limits
`xfun::tinify()`	Yes	No	Yes	Yes	500 files/month (free tier)
`xfun::optipng()`	Yes	Yes	No	No	No
tinieR	No	No	Yes	Yes	500 files/month (free tier)
tinyimg	Yes	Yes	No	No	No
optout	No	Yes	No	No	No
resmush	Yes	No	Yes	No	Maximum size: 5 MB

Table 1: R packages: comparison of image optimization alternatives.

Tool	png	jpg	gif	bmp	tiff	webp	pdf
`xfun::tinify()`	✅	✅	❌	❌	❌	✅	❌
`xfun::optipng()`	✅	❌	❌	❌	❌	❌	❌
tinieR	✅	✅	❌	❌	❌	✅	❌
tinyimg	✅	✅	❌	❌	❌	❌	❌
optout	✅	✅	❌	❌	❌	❌	✅
resmush	✅	✅	✅	✅	✅	❌	❌

Table 2: R packages: supported formats.

References

Xie, Yihui. 2024. xfun: Supporting Functions for Packages Maintained by Yihui Xie. https://github.com/yihui/xfun.

Xie, Yihui. 2026. tinyimg: Optimize and Compress Images. https://doi.org/10.32614/CRAN.package.tinyimg.