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resmush

resmush is a R package that allows users to optimize and compress images using reSmush.it. reSmush.it is a free API that provides image optimization and has been implemented in WordPress and many other tools.

Some of the features of reSmush.it include:

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

Installation

Install resmush from CRAN with:

install.packages("resmush")

Example

Compressing an online jpg image:

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 with size 178.7 Kb
#> ✔ Success for 1 url: Size now is 45 Kb (was 178.7 Kb). Saved 133.7 Kb (74.82%).
#> See result in directory 'man/figures'.

Original uncompressed file (a)

Optimized file (b)

Figure 1: Original picture (a): 178.7 Kb; Optimized picture (b): 45 Kb (Compression: 74.8%). Click to enlarge.

The compression quality for jpg files can be adjusted using the qlty argument. However, it is recommended to keep this value above 90 to maintain good image quality.

# Extreme case
resmush_url(
  url,
  outfile = "man/figures/jpg_example_compress_low.jpg",
  overwrite = TRUE,
  qlty = 3
)
#> ══ resmush summary ═════════════════════════════════════════════════════════════
#> ℹ Input: 1 url with size 178.7 Kb
#> ✔ Success for 1 url: Size now is 2.2 Kb (was 178.7 Kb). Saved 176.4 Kb (98.74%).
#> See result in directory 'man/figures'.

Low quality figure

Figure 2: Low quality image due to a high compression rate.

All the functions return (invisibly) a dataset summarizing the process. The following example shows how this works when compressing a local file:

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

# For the example, copy to a temporary file
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

Other alternatives

Several other R packages also provide image optimization tools:

tool CRAN Additional software? Online? API Key? 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)
optout No Yes No No No
resmush Yes No Yes No Max size 5 MB

Table 1: R packages: Comparison of alternatives for optimizing images.

tool png jpg gif bmp tiff webp pdf
xfun::tinify() ✅ ✅ ❌ ❌ ❌ ✅ ❌
xfun::optipng() ✅ ❌ ❌ ❌ ❌ ❌ ❌
tinieR ✅ ✅ ❌ ❌ ❌ ✅ ❌
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 is

@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 = {0.2.2},
  url = {https://dieghernan.github.io/resmush/},
  abstract = {Compress local and online images using the reSmush.it API service <https://resmush.it/>.},
}

References

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