Theia

A Ruby gem to

1. Transform website URL into PNGs or JPEGs using Puppeteer.
2. Compare two images using Node JS Library Pixelmatch
3. Compress an image using Sharp Sharp

Installation

Ruby Dependencies

Add this line to your application's Gemfile:

gem 'theia'

Node dependencies

nvm use 10.16.3
npm install puppeteer pixelmatch sharp

Usage

Screenshot [Google Puppeteer]

# Theia screenshot accepts a valid website URL for initialization.
theia_screenshot = Theia::Screenshot.new(<website_url>)

# Get a screenshot
png = theia_screenshot.to_png(<save_location>, options)
jpeg = theia_screenshot.to_jpeg(<save_location>, options) 

<save_location> must be in the format of output_file.png or output_file.jpg

Options

options is an object literal with the following properties:

• full_page When true, takes a screenshot of the full scrollable page. Defaults to false, values: true/false
• device Devices which will be used to generate screenshot, values: mobile, iphone, ipad, desktop and their respective landscapes by appending _landscape
• url Valid website URL, eg: https://www.google.com
• quality The quality of the image, between 0-100. Not applicable to png images, values: 0-100
• omit_background Hides default white background and allows capturing screenshots with transparency. Defaults to false, values: true/false

Image Compare [Pixelmatch]

theia_compare = Theia::ImageCompare.new

# Compare 2 pngs
theia_compare.compare(<file1.png>, <file2.png>, <output.png>, options)

Only PNG compare is supported now. JPEG will be added in the near future.

Options

options is an object literal with the following properties:

• threshold Matching threshold, ranges from 0 to 1. Smaller values make the comparison more sensitive. 0.1 by default.
• include_a_a If true, disables detecting and ignoring anti-aliased pixels. false by default.
• alpha Blending factor of unchanged pixels in the diff output. Ranges from 0 for pure white to 1 for original brightness. 0.1 by default.
• aa_color The color of anti-aliased pixels in the diff output in [R, G, B] format. [255, 255, 0] by default.
• diff_color The color of differing pixels in the diff output in [R, G, B] format. [255, 0, 0] by default.
• diff_mask Draw the diff over a transparent background (a mask), rather than over the original image. Will not draw anti-aliased pixels (if detected).

Compares two images, writes the output diff and returns the number of mismatched pixels.

Image Compress [Sharp]

theia_compress = Theia::ImageCompress.new(<image_type>)

# Compress an image
theia_compare.compress(<file1>, <output>, options)

Currently png and jpeg images are supported.

options is an object literal with the following properties:

• compression_level zlib compression level, 0-9 (optional, default 9). Only for PNGs
• quality Use the lowest number of colours needed to achieve given quality, requires libvips compiled with support for libimagequant (optional, default 100)
• force Boolean force JPEG/PNG output, otherwise attempt to use input format (optional, default true)
• adaptive_filtering Use adaptive row filtering (optional, default false)
• palette Quantise to a palette-based image with alpha transparency (boolean)
• colours Maximum number of palette entries, requires libvips compiled with support for libimagequant (optional, default 256)
• progressive Only for JPEG. Use progressive (interlace) scan (optional, default false)
• optimise_coding Only for JPEG. Optimise Huffman coding tables (optional, default true)

Contributions

Feel free to send suggestions, point out issues, or submit pull requests.