Imagekit Ruby and Rails SDK

ImageKit gem for Ruby on Rails that allows you to use real-time image resizing, optimization, and file uploading.

Table of contents -

• Installation
• Initialization
• URL Generation
• File Upload
• File Management
• Utility Functions
• Sample applications
• Support
• Links

Quick start guide

Get started with official quick start guide for integrating ImageKit in Ruby on Rails.

Installation

Add imagekitio dependency to your application's Gemfile:

gem 'imagekitio'

And then execute:

$ bundle install

Or install it yourself:

$ gem install imagekitio

Initialization

Add this configuration to config/environments/development.rb and config/environments/production.rb

config.imagekit={
  private_key: "<your-private-key>",
  public_key: "<your-public-key>",
  url_endpoint: "<endpoint-url>"
}

You can create a carrierwave uploader in order to attach pictures to your database objects as their attributes. To upload images without designating them as database attributes, skip to this section.

rails g uploader <Uploading_attribute_name>
# For example, if you want to create an uploader for Avatar attribute, then use
rails g uploader Avatar
# Generated uploader's path will be app/uploaders/avatar_uploader.rb

After that, you need to edit your generated uploader and make the following changes:

# Set store as imagekit_store
storage :imagekit_store

# If you want to add uploading options, then create this method inside the uploader file as an example

def options
    options={
        response_fields: 'isPrivateFile, tags',
        tags: %w[abc def],
        use_unique_file_name: false,
        folder: "your_directory/"
    }
end

# If you want to set upload dir, then you can use the following method, or you can also use the options method.
# This method should return a string
def store_dir
    "your_directory/"
end

Then you need to modify your model. for example- if your model name is employee, then do these changes.

class Employee < ApplicationRecord
    attr_accessor :avatar
    mount_uploader :avatar, AvatarUploader
end

Get image url:

# If @employee is an object of your model that has data.

# To get the original image url, use
@employee.avatar.url

# And to get transformed url use
# options is a transformation options
@employee.avatar.url_with(options)

Usage

You can use this Ruby SDK for three different kinds of methods - URL generation, file upload, and file management.

The usage of the SDK has been explained below.

URL generation

1. Using Image path and image hostname or endpoint

This method allows you to create a URL using the path where the image exists and the URL endpoint(url_endpoint) you want to use to access the image. You can refer to the documentation here to read more about URL endpoints in ImageKit and the section about image origins to understand about paths with different kinds of origins.

image_url = imagekitio.url({
    path: "/default-image.jpg",
    url_endpoint: "https://ik.imagekit.io/your_imagekit_id/endpoint/",
    transformation: [{height: "300", width: "400"}]
})

The result in a URL like

https://ik.imagekit.io/your_imagekit_id/endpoint/tr:h-300,w-400/default-image.jpg

2.Using full image URL This method allows you to add transformation parameters to an existing, complete URL that is already mapped to ImageKit using src parameter. This method should be used if you have the complete image URL mapped to ImageKit stored in your database.

image_url = imagekitio.url({
    src: "https://ik.imagekit.io/your_imagekit_id/endpoint/default-image.jpg",
    transformation: [{height: "300", width: "400"}],
})

The results in a URL like

https://ik.imagekit.io/your_imagekit_id/endpoint/default-image.jpg?tr=h-300%2Cw-400

The .url() method accepts the following parameters

Option	Description
url_endpoint	Optional. The base URL to be appended before the path of the image. If not specified, the URL Endpoint specified at the time of SDK initialization is used. For example, https://ik.imagekit.io/your_imagekit_id/endpoint/
path	Conditional. This is the path at which the image exists. For example, /path/to/image.jpg. Either the path or src parameter needs to be specified for URL generation.
src	Conditional. This is the complete URL of an image already mapped to ImageKit. For example, https://ik.imagekit.io/your_imagekit_id/endpoint/path/to/image.jpg. Either the path or src parameter needs to be specified for URL generation.
transformation	Optional. An array of objects specifying the transformation to be applied in the URL. The transformation name and the value should be specified as a key-value pair in the object. Different steps of a chained transformation can be specified as different objects of the array. The complete list of supported transformations in the SDK and some examples of using them are given later. If you use a transformation name that is not specified in the SDK, it gets applied as it is in the URL.
transformation_position	Optional. The default value is path that places the transformation string as a path parameter in the URL. It can also be specified as query, which adds the transformation string as the query parameter tr in the URL. If you use src parameter to create the URL, then the transformation string is always added as a query parameter.
query_parameters	Optional. These are the other query parameters that you want to add to the final URL. These can be any query parameters and not necessarily related to ImageKit. Especially useful if you want to add some versioning parameter to your URLs.
signed	Optional. Boolean. Default is false. If set to true, the SDK generates a signed image URL adding the image signature to the image URL. This can only be used if you are creating the URL with the url_endpoint and path parameters and not with the src parameter.
expire_seconds	Optional. Integer. Meant to be used along with the signed parameter to specify the time in seconds from now when the URL should expire. If specified, the URL contains the expiry timestamp in the URL, and the image signature is modified accordingly.

Examples of generating URLs

1. Chained Transformations as a query parameter

image_url = imagekitio.url({
    path: "/default-image.jpg",
    url_endpoint: "https://ik.imagekit.io/your_imagekit_id/endpoint/",
    transformation: [{
        height: "300",
        width: "400"
    },{
        rotation: 90
    }],
    transformation_position: "query"
})

Sample Result URL -

https://ik.imagekit.io/your_imagekit_id/endpoint/default-image.jpg?tr=h-300%2Cw-400%3Art-90

2. Sharpening and contrast transforms and a progressive JPG image

There are some transforms like Sharpening that can be added to the URL with or without any other value. To use such transforms without specifying a value, specify the value as "-" in the transformation object. Otherwise, specify the value that you want to be added to this transformation.

image_url = imagekitio.url({
    src: "https://ik.imagekit.io/your_imagekit_id/endpoint/default-image.jpg",
    transformation: [{
        format: "jpg",
        progressive: "true",
        effect_sharpen: "-",
        effect_contrast: "1"
    }]
})

//Note that because `src` parameter was used, the transformation string gets added as a query parameter `tr`
https://ik.imagekit.io/your_imagekit_id/endpoint/default-image.jpg?tr=f-jpg%2Cpr-true%2Ce-sharpen%2Ce-contrast-1

3. Signed URL that expires in 300 seconds with the default URL endpoint and other query parameters

image_url = imagekit.url({
    path: "/default-image",
    query_parameters: {
                "v": "123"
    },
    transformation: [{
        height: "300",
        width: "400"
    }],
    signed: True,
    expire_seconds: 300
})

Sample Result URL

https://ik.imagekit.io/your_imagekit_id/tr:h-300,w-400/default-image.jpg?v=123&ik-t=1567358667&ik-s=f2c7cdacbe7707b71a83d49cf1c6110e3d701054

List of transformations

The complete list of transformations supported and their usage in ImageKit can be found here. The SDK gives a name to each transformation parameter, making the code simpler, making the code simpler, and readable. If a transformation is supported in ImageKit, but a name for it cannot be found in the table below, then use the transformation code from ImageKit docs as the name when using the url function.

Supported Transformation Name	Translates to parameter
height	h
width	w
aspectRatio	ar
quality	q
crop	c
cropMode	cm
x	x
y	y
focus	fo
format	f
radius	r
background	bg
border	b
rotation	rt
blur	bl
named	n
overlayX	ox
overlayY	oy
overlayFocus	ofo
overlayHeight	oh
overlayWidth	ow
overlayImage	oi
overlayImageTrim	oit
overlayImageAspectRatio	oiar
overlayImageBackground	oibg
overlayImageBorder	oib
overlayImageDPR	oidpr
overlayImageQuality	oiq
overlayImageCropping	oic
overlayImageTrim	oit
overlayText	ot
overlayTextFontSize	ots
overlayTextFontFamily	otf
overlayTextColor	otc
overlayTextTransparency	oa
overlayAlpha	oa
overlayTextTypography	ott
overlayBackground	obg
overlayTextEncoded	ote
overlayTextWidth	otw
overlayTextBackground	otbg
overlayTextPadding	otp
overlayTextInnerAlignment	otia
overlayRadius	or
progressive	pr
lossless	lo
trim	t
metadata	md
colorProfile	cp
defaultImage	di
dpr	dpr
effectSharpen	e-sharpen
effectUSM	e-usm
effectContrast	e-contrast
effectGray	e-grayscale
original	orig

File Upload

This method can be used to directly upload images to your ImageKit Media Library without giving it the designation of an attribute of any database object.

The SDK provides a simple interface using the .upload() method to upload files to the ImageKit Media library. It accepts all the parameters supported by the ImageKit Upload API.

The upload() method requires at least the file and the file_name parameter to upload a file and returns a callback with the error and result as arguments. You can pass other parameters supported by the ImageKit upload API using the same parameter name as specified in the upload API documentation. For example, to specify tags for a file at the time of upload, use the tags parameter as specified in the documentation here.

Simple usage

imagekitio.upload_file(
    file = "<url|base_64|binary>", # required
    file_name= "my_file_name.jpg",  # required
    options= {response_fields: 'isPrivateFile, tags', tags: %w[abc def], use_unique_file_name: true,}
)

If the upload is succeeded, error will be None, and the result will be the same as what is received from ImageKit's servers. If the upload fails, error will be the same as what is received from ImageKit's servers, and the result will be None.

File Management

The SDK provides a simple interface for all the media APIs mentioned here to manage your files. This also returns error and result. The error will be None if API succeeds.

1. List & Search Files

Accepts an object specifying the parameters to be used to list and search files. All parameters specified in the documentation here can be passed with the correct values to get the results.

imagekitio.list_files({skip: 0, limit: 5})

2. Get File Details Accepts the file ID and fetches the details as per the API documentation here

imagekitio.get_file_details(file_id)

3. Get File Metadata Accepts the file ID and fetches the metadata as per the API documentation here

imagekit.get_file_metadata(file_id)

3. Get File Metadata from remote url Accepts the remote file url and fetches the metadata as per the API documentation here

imagekit.get_remote_file_url_metadata(remote_file_url)

4. Update File Details Update parameters associated with the file as per the API documentation here. The first argument to the update_field_details method is the file ID, and a second argument is an object with the parameters to be updated.

imagekitio.update_file_details(file_id, {
    tags: ["image_tag"],
    custom_coordinates: "10,10,100, 100"
})

6. Delete file Delete a file as per the API documentation here. The method accepts the file ID of the file that has to be deleted.

imagekitio.delete_file(file_id)

6. Bulk File Delete by IDs Delete a file as per the API documentation here. The method accepts a list of file IDs of files that has to be deleted.

imagekitio.bulk_file_delete(["file_id1", "file_id2"])

6. Purge Cache Programmatically issue a cache clear request as pet the API documentation here. Accepts the full URL of the file for which the cache has to be cleared.

imagekitio.purge_file_cache(full_url)

7. Purge Cache Status

Get the purge cache request status using the request ID returned when a purge cache request gets submitted as pet the API documentation here

imagekitio.get_purge_file_cache_status(cache_request_id)

Utility functions

We have included the following commonly used utility functions in this package.

Authentication parameter generation

In case you are looking to implement client-side file upload, you are going to need a token, expiry timestamp, and a valid signature for that upload. The SDK provides a simple method that you can use in your code to generate these authentication parameters for you.

Note: The Private API Key should never be exposed in any client-side code. You must always generate these authentication parameters on the server-side

authentication_parameters = imagekit.get_authentication_parameters(token, expire)

Returns

{
    "token": "unique_token",
    "expire": "valid_expiry_timestamp",
    "signature": "generated_signature"
}

Both the token and expire parameters are optional. If not specified, the SDK uses the uuid to generate a random token and also generates a valid expiry timestamp internally. The value of the token and expire used to generate the signature is always returned in the response, no matter if they are provided as an input to this method or not.

Distance calculation between two pHash values

Perceptual hashing allows you to construct a hash value that uniquely identifies an input image based on the contents of an image. imagekit.io metadata API returns the pHash value of an image in the response. You can use this value to find a duplicate near the duplicate(similar) image by calculating the distance between the two images.

This SDK exposes the phash_distance function to calculate the distance between two pHash value. It accepts two pHash hexadecimal strings and returns a numeric value indicative of the level of difference between the two images.

def calculate_distance():
    # fetch metadata of two uploaded image files
    ...
    # extract pHash strings from both: say 'first_hash' and 'second_hash.'
    ...
    # calculate the distance between them:

    distance = imagekitio.phash_distance(first_hash, second_hash)
    return distance

Distance calculation examples

imagekitio.phash_distance('f06830ca9f1e3e90', 'f06830ca9f1e3e90')
# output: 0 (ame image)

imagekitio.phash_distance('2d5ad3936d2e015b', '2d6ed293db36a4fb')
# output: 17 (similar images)

imagekitio.phash_distance('a4a65595ac94518b', '7838873e791f8400')
# output: 37 (dissimilar images)

Sample Application

There are two sample apps:

• Rails application using Carrierwave
• Plain ruby application

Instructions for a rails application

This is under samples/rails_app directory. Follow the instructions below to set up a rails application.

1. Clone git repository

git clone `https://github.com/imagekit-developer/imagekit-gem

2. Go to sample project directory

cd sample/rails_app

3. Write imagekit configuration in config/environments/development.rb

config.imagekit={
  private_key: "<your-private-key>",
  public_key: "<your-public-key>",
  url_endpoint: "<endpoint-url>"
}

4. Install dependency

bundle install

This sample project is using the Sqlite3 database. If you are getting sqlite3 gem installation error, then install sqlite3 first, then again run bundle install.

5. Migrate the database

bundle exec rake db:migrate

6. Run your application

rails s

It will run on your default rails port [3000]. Sample Application URL: http://localhost:3000/posts/

Instructions for ruby application

Run following command under samples/ruby_app directory

ruby app.rb

Support

For any feedback or to report any issues or general implementation support, please reach out to [email protected]

Links

• Documentation
• Main website

License

Released under the MIT license.