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.

Installation

Check the documentation for the development version at https://dieghernan.github.io/resmush/dev/.

You can install the development version of resmush from GitHub with:

# install.packages("pak")
pak::pak("dieghernan/resmush")

Alternatively, install resmush from r-universe:

# Install resmush in R:
install.packages(
  "resmush",
  repos = c(
    "https://dieghernan.r-universe.dev",
    "https://cloud.r-project.org"
  )
)

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 = "man/figures/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 'man/figures'.

(a)

(b)

Figure 1: Original image (a): 178.7 KB, optimized image (b): 45 KB (compression: 74.8%). Click to enlarge.

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 = "man/figures/jpg_example_compress_low.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 'man/figures'.

Figure 2: Image with visible compression artifacts caused by high compression (qlty = 3).

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.

Citation

Hernangómez D (2026). resmush: Optimize and Compress Image Files with reSmush.it. doi:10.32614/CRAN.package.resmush. https://dieghernan.github.io/resmush/.

A BibTeX entry for LaTeX users:

@Manual{R-resmush,
  title = {{resmush}: Optimize and Compress Image Files with {reSmush.it}},
  doi = {10.32614/CRAN.package.resmush},
  author = {Diego Hernangómez},
  year = {2026},
  version = {1.0.0.9000},
  url = {https://dieghernan.github.io/resmush/},
  abstract = {Optimize and compress local image files, directories and online images with the reSmush.it API <https://resmush.it/>. Supports png, jpg/jpeg, gif, bmp and tiff files.},
}

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.