Tinyimg

Load a JPEG or PNG, get its dimensions, crop it, resize it, and extract it again as either a JPEG or PNG.

This gem can work from image data stored in memory, as well as from a file or IO stream. It's been coded to be as efficient as possible, so doesn't use temporary files.

Tinyimg uses libgd for its image processing. libgd is significantly less painful to install than ImageMagick and friends! Other than that, all that is required is Ruby 2.0+.

If you don't already have libgd installed on your system, install it.

On OS X, install Homebrew and

brew install libgd

On a Linux system, use your package manager. For example, on Debian/Ubuntu:

sudo apt-get install libgd-dev

Then add tinyimg to your project's Gemfile

gem 'tinyimg'

Load the image with the method that fits your use case:

image = Tinyimg.from_string(an_image_that_is_already_loaded)
image = Tinyimg.from_file("some_image.png")
image = Tinyimg.from_io(params[:uploaded_file])

Resize it by using one of these methods:

image.resize_exact!(100, 100)   # forces image to be exactly 100x100
image.resize!(width: 100)       # width = 100 and aspect ratio maintained
image.resize!(height: 50)       # height = 50 and aspect ratio maintained
image.resize_to_fit!(100, 100)  # image will be 100x100 maximum
image.resize_to_fill!(100, 100) # image will be 100x100 minimum

Crop it using this method:

# Crops the image from (20, 20) to (70, 70), resulting in a 50x50 image.
image.crop!(x: 20, y: 20, width: 50, height: 50)

# By default, x and y arguments are zero, and width and height arguments
# are the width and height of the original image.
image.crop!(width: image.height)

Set the transparent color of your PNG image if you're about to save it to a JPEG, as JPEG doesn't support transparency:

# Make the transparent color red
image.fill_transparent_color!(255, 0, 0)

Then get an image back:

image.to_png                 # returns a string
image.to_jpeg                # returns a string
image.save("some_image.jpg") # file type auto-determined by extension

You can ask for the image's dimensions:

image.width       # => 120
image.height      # => 80
image.dimensions  # => [120, 80]

You can also use the non-! versions of the operation methods: resize_exact, resize, resize_to_fit, resize_to_fill, crop and fill_transparent_color. These create a new image in memory and return it, leaving the old image untouched. This is useful if you want to resize an original image to multiple sizes. Using these methods will take more memory.

Take an uploaded file that's a PNG or JPEG, make the transparent color white, save the original as a JPEG, then resize to create a thumbnail and save that too:

Tinyimg
  .from_io(params[:uploaded_file])
  .fill_transparent_color!(255, 255, 255)
  .save("#{path}/full_size.jpg")
  .resize_to_fit!(100, 100)
  .save("#{path}/thumbnail.jpg")

Load a file from disk, make a thumbnail, and return it as a JPEG so we can save it into our database:

data = Tinyimg.from_file(image_filename).resize_to_fit!(100, 100).to_jpeg
user.update!(thumbnail_image: data)

Copyright 2015-2016 Roger Nesbitt. Licenced under the MIT licence.