Image resizer

A Ruby app to resize images built with the Sinatra web framework and ImageMagick library.

Resizing images

The endpoint for resizing images is /image and it requires the params posted as multi-part form data.

• image_file the image to be resized
• width max width of the resized image in pixels. Defaults to 800
• height max height of the resized image in pixels. Defaults to 800

Images will be resized maintaining their aspect ratio.

Images that or not a png, gif, svg or jpeg will be converted to a png. The full list of supported image types is whatever installed version of imagemagick supports (`identify -list format).

SVG images will be optimised, but not have their dimensions modified.

Local development

You will need to install the dependencies for the Ruby image_processing gem. Here is the homebrew command for installing imagemagick on a mac.

# install dependencies
brew install imagemagick

# install app
bundle install

# start
rackup

# Lint
bundle exec rubocop

# Test
bundle exec rspec

Docker development

# Build
docker build -t citizensadvice/image-resizer .

# Test
docker compose run --rm app bundle exec rspec

# Start
docker compose up

The url is http://localhost:4567

Visiting this in a web browser displays a liveness message to confirm the service is running.

PNG

curl -X POST -F mime_type='image/png' -F image_file=@"./spec/fixtures/image_files/test-png-1102x1287px.png" http://localhost:4567/image --output test-png-image-resized.png

GIF

curl -X POST -F mime_type='image/gif' -F image_file=@"./spec/fixtures/image_files/test-gif-1102x1287px.gif" http://localhost:4567/image --output test-gif-image-resized.gif

JPEG

curl -X POST -F mime_type='image/jpeg' -F image_file=@"./spec/fixtures/image_files/test-jpg-1102x1287px.jpg" http://localhost:4567/image --output test-jpg-image-resized.jpg

TIFF

For images in the TIFF format they are automatically converted to PNG, so here is an example for this scenario.

curl -X POST -F mime_type='image/tiff' -F image_file=@"./spec/fixtures/image_files/test-bad-tif-800x1000px.tif" http://localhost:4567/image --output test-tif-image-resizer.png